Sunday, August 29, 2010

The Horse | Stone Bruises

The Horse Stone Bruises

I thought this might be of interest to those of you suffering the headache of a horse with a sole bruise.
Dr. C

Thursday, April 29, 2010

4/28/2010 Equine Melanoma

Vet tip of the Day: Equine Melanoma
Key Words: Melanoma, skin tumor, metastasis, cisplatin, cimetidine, laser

Many of you may have had experience over the years with melanoma in grey horses.  This form of melanoma, the dermal melanoma, is a very common skin tumor, usually slow growing, and usually confined to the site of origin.  Dermal melanomas are tumors of the black pigment cells, melanin cells, that are present in high numbers in the skin of grey horses.  The tumors typically are round, hard, and dense black when cut open.  They occur most frequently around the tail base and rectum, but also are seen in the throat latch region and at the base of the ear, where they most commonly arise in the parotid salivary gland.  While dermal melanomas often are solitary, some horses are afflicted with multiple tumors.  This condition is called dermal melanomatosis, and horses with multiple melanomas are more likely to have metastasis of tumors to remote locations, including lymph nodes, liver, spleen, and skeletal muscle.  Surgical removal of individual tumors in such horses may be locally curative, but the remaining tumors continue to grow and more tumors may develop.
There are two less common types of melanomas that occur in horses. The first is the melanocytic nevus, which is a benign tumor that occurs as a single, discrete, nodular mass in young horses. They may arise anywhere on the body and when removed surgically rarely recur.  At the other end of the spectrum are anaplastic malignant melanomas, which occur in older horses (usually over 20 years of age) of any color.  These tumors are uncommon, but usually metastasize to distant sites within a year and carry a poor prognosis.

While most horses with dermal melanomas tolerate them well, occasionally these tumors can be life threatening.  This happens most often when the tumors metastasize and grow in internal organs, or when they become so large that they cause mechanical obstruction to breathing in the throat region or impair defecation by obstructing the anus.

Dermal melanomas present an excellent example of how variable the behavior of tumors can be in different species.  As you probably are aware, melanoma in people often presents as a highly malignant tumor which may carry a poor prognosis for long term survival, even in the face of aggressive treatment.  Similarly, in dogs, oral melanoma is a malignant neoplastic process with a high fatality rate.  Many of you knew my wonderful dog Sticky, who died last year within three months of her diagnosis with malignant melanoma.  Luckily for our horses, this is NOT the case with equine dermal melanoma.  However, the common occurrence of melanoma in horses has made it a useful research tool for scientists investigating treatments for melanoma in other species.

One of the areas of intense investigation is the role of the immune system (immunomodulation) in treating melanomas in humans, dogs, and to a lesser degree, horses.  There is a melanoma vaccine currently under conditional license for malignant melanoma in dogs which I gave to Sticky during her treatment.  There also have been limited investigations using vaccines made directly from tumors removed from a particular horse then administered back to the same horse to control widespread melanomas. However, at this time there is no commercially available equine melanoma vaccine and the use of individual melanoma vaccines is not considered standard therapy.

There are many medications used for other purposes which exhibit immunomodulatory activity in addition to their primary mode of action.  One of these is cimetidine.  Cimetidine is an H2 histamine antagonist which reduces acid production in the stomach and is available over the counter as Tagamet, used in people and horses to treat gastric ulcers.  Cimetidine also acts in several complex ways to alter the body's immune  response to certain neoplastic (cancerous) processes.  It has been used with some success in the treatment of equine dermal melanoma at a dosage of 2.5 mg/kg given orally every 8 hours.  Unfortunately, after some promising initial studies, it appears that the activity of cimetidine against equine melanomas is very variable from horse to horse.  While the medication is unlikely to have adverse effects, its efficacy in each case is unpredictable, and therefore, it also no longer is widely used in the treatment of melanomas.

Dr. Robertson, a veterinarian at the Virginia Tech School of Veterinary Medicine did his PhD research on comparative melanoma (across species) and continues to conduct clinical research using Frankincense Oil as an immunomodulatory agent in the treatment of equine melanoma.  The oil is injected into the tumors and causes their regression.  The overall effectiveness of this treatment is not yet determined, but it is an interesting avenue holding promise for the future.  

In addition to immunomodulation, chemotherapy has been used in the treatment of equine melanoma. One chemotherapy agent used in horses is cisplatin, which is very effective in the treatment of squamous cell carcinoma (blog coming up on this soon).  Cisplatin has poor effectiveness against melanomas in dogs and people, but has been used with success in at least one clinical trial in horses.  In this study, 13/14 horses with melanoma had a positive response to the implantation of slow release cisplatin beads into the tumor mass.

The definitive treatment for melanomas is wide surgical excision.  With the advent of surgical lasers, it has become possible to remove larger tumors in challenging anatomic locations, such as the parotid salivary gland.
Traditionally, many veterinarians do not recommend the removal of small melanomas when they are first detected.  I disagree with this approach.  Melanomas tend to be very well isolated and complete surgical excision is often possible when the tumors are addressed early and are relatively small.  While excision does not prevent the development of new tumors at other sites, in my experience recurrence of the tumor at the site of excision is rare.

In summary, if you have a grey horse with melanomas, ask your veterinarian to evaluate them. I strongly recommend early surgical removal.  Consider cimetidine as an adjunctive therapy because it is safe, and may be effective.  Cimetidine can be obtained from reputable compounding pharmacies at a reasonable price.   For more advanced tumors, discuss the options of laser surgery and/or cisplatin bead implantation and consider seeking the opinion of a  veterinary specialist, an ACVS boarded surgeon and/or ACVIM boarded large animal internist.

I believe that education is the key to evolution. I believe that animals are the key to compassion. I believe the learning never stops.

Sunday, April 25, 2010

4/25/2010 Euthanasia Part III: Making the Decision

 Vet tip of the Day: When is it the right time for euthanasia?

In this final entry concerning the difficult topic of euthanasia, I would like to share with you my views as a veterinarian on the hardest part of the decision for euthanasia: when is the appropriate time?

First and foremost, I respect the right of a horse's owner to use their own judgement in deciding what they believe is best for their horse.  Horses legally are considered property, they do not have legal rights.  There are governing bodies in every state to respond to situations of animal cruelty to protect horses from abuse situations, but elective euthanasia is not considered abuse. I do not agree with every decision for euthansia, and I have refused to perform euthansia in rare cases.  However, the vast majority of owners who come to the decision to end their horse's life do so after careful and painful deliberation, and are acting in the best interest of their cherished animal.

I am frequently asked by clients to help them in making the decision to end a horse's life.  Usually this is in the case of geriatric horses, or chronically lame horses.  I would love to be able to tell you that it is always clear to me when a horse is suffering inhumanely, but it isn't.  The question of quality of life is engulfed in a huge grey cloud. Two things that I offer as factors to consider when you are trying to determine the quality of a debilitated or geriatric horse's life are: 1) progressive weight loss in the face of an excellent plane of nutrition and 2) prolonged periods of recumbency (lying down) to the point that pressure points such as hips develop non-healing sores, and the horse has pronounced difficulty rising.

The subject of euthanasia for practical reasons is really problematic.  Horses live a long time and they are very expensive to care for.  As horses age they typically require more calories and special dietary considerations, as well as nutritional supplements and sometimes medication (such as pergolide for Cushings horses, or anti-inflammtories for musculoskeletal problems) which increase the cost of upkeep for an animal that may no longer be rideable.  I stick very firmly to my respect for each horse owner's individual right to make decisions for such horses.

On the other end of the spectrum are owners who simply do not believe in euthanasia, and feel very strongly that all living beings should die a natural death.  Again, I respect this perspective, as long as the owner is able to provide adequate nursing care and pain medication to support their horse through the process of dying.  I always remember a foal I treated back at the University of Georgia when I was a resident.  The owner had lost a son to a long battle with cancer and absolutely would not consider euthanasia an option for this foal.  The foal suffered from neonatal septicemia, a bacterial infection that circulated throughout the body, seeding infections in multiple sites.  The foal had bacterial endocarditis (a vegetative bacterial growth on a heart valve), pneumonia, an infected umbilical cord, and an infection of the growth plate adjacent to one of the hind fetlock joints.  The bacteria responsible for all these infections was resistant to virtually every antibiotic available.  Statistically the foal's chance of survival was way below 10%, he was extremely lame, had dramatically reduced exercise capacity due to his enlarged heart and leaky mitral valve, as well as the severe pnuemonia.

Despite my repeated explanations of the foal's condition and poor quality of life, the owner refused to consider euthanasia, and instructed me to continue treating the foal, regardless of cost or prognosis.  Well guess what?  That foal lived to race as a 3 year old - he only raced once, and not very well, but he managed to overcome his heart infection, and although he never was sound, he was retired after his one race and lived out his life in a beautiful pasture. It is not our place to judge the decisions of others regarding their horses, unless cruelty or neglect are evident.

So when is it appropriate to choose euthanasia for your horse?  Only you can make that decision.  Listen to your veterinarian's assessment of your horse's condition and prognosis, then search your heart and mind and make your decision based on your own personal ethical code.  It is never easy, and it never gets easier, but it is part of the responsibility of horse ownership. 

I believe that education is the key to evolution. 
I believe that animals are the key to compassion.
I believe the learning never stops.

Thursday, April 22, 2010

4/22/2010 The mechanics of euthansia

Vet tip of the Day: Euthanasia - What really happens
Key Words: Barbiturate, gunshot, cerebral cortex
Yesterday's euthanasia stories came straight from the heart.  Today I'd like to take a step back and discuss this difficult topic from a more detached perspective. Much of what will be included in todays' blog was taken directly from the American Veterinary Medical Association Guidelines on Euthanasia published in 2000.  If you want to read them in more detail, they are available on line.

The word euthanasia is derived from two Greek words.  The first, "eu" means "good" and the second, "thanatos" means "death".  Thus the word means "good death" or the act of inducing humane death in an animal.  One of the greatest concerns expressed by owners with respect to euthanasia is their animal's state of consciousness during the transition from life to death.  The AVMA makes it very clear that any appropriate form of euthanasia should result in a rapid loss of consciousness and that the loss of consciousness should occur before, or simultaneously with, loss of motor control.  In most cases, equine euthanasia is performed with an injectable barbiturate, usually sodium pentobarbital.  This drug acts very rapidly, causing central nervous system depression beginning in the cerebral cortex.  The cortex is the center of consciousness, so the first thing that happens when a horse receives a large dose of sodium pentobarbital is an immediate loss of awareness.  The drug then rapidly depresses the lower brain centers, resulting in apnea, or failure to breathe, and cardiac arrest. 

The horse may sink quietly to the ground after the euthanasia injection is administered, but this cannot be guaranteed.  Sometimes the animal becomes rigid and may even fall over backwards.  It can be very disturbing to watch such a large animal hit the ground, but REMEMBER THAT THE HORSE IS UNCONSCIOUS AND UNAWARE.  The physical process of dying may include several gasping breaths, muscle trembling, and voiding.  These activities are natural physical processes that accompany the shutting down of body systems and even though they involve motor activity, or physical movement, they occur AFTER the cortex has stopped functioning and the animal has lost consciousness.

Sometimes owners request that their horse be sedated prior to euthanasia.  If the horse is extremely excited or difficult to handle, this is appropriate.  However, in general I try to avoid sedation if possible.  Sedatives slow the heart rate and decrease cardiac output, thereby slowing the delivery of barbiturate to the brain.  Euthanasia is most often performed on very sick or very old horses, which may already have impaired cardiovascular function.  The goal is to get the largest amount of barbiturate into the horse's brain as quickly as possible to achieve immediate and complete loss of consciousness.  Sedation can compromise this process.

Finally I'd like to address the issue of using firearms to perform euthanasia.  The following is quoted directly from the AVMA Guidelines on Euthanasia (note the term "physical methods" includes firearms and captive bolt pistols):

"When properly used by skilled personnel with well-maintained equipment, physical methods of euthanasia may result in less fear and anxiety and be more rapid, painless, humane and practical than other forms of euthanasia.  Some consider physical methods of euthanasia aesthetically displeasing.  There are occasions, however, when what is perceived as aesthetic and what is most humane are in conflict."

The term "physical methods" includes captive bolt pistols and gunshot.  Most of us have a natural fear of guns and are very upset by the violence associated with the act of shooting an animal, especially one we have loved and cared for. Horses do not share this aversion.  When performed safely and correctly, death by a bullet into the brain is instantaneous and therefore, painless.  It should never be considered unless the person handling the firearm is skilled not only with the weapon, but also absolutely understands the anatomy of the horse's head and how the shot should be placed. 

These are difficult things to think about, but I believe that understanding the process is an important part of making the decision to end a life.  This decision, when you face it, is about the quality of your horse's life.  It is painful, and sad, but it also is part of the responsibility of owning animals.  Now that we have examined the physical realities of euthanasia, tomorrow I will conclude this topic with some more philosophical thoughts on reaching the decision for euthanasia of your horse.

I believe that education is the key to evolution.
I believe that animals are the key to compassion.
I believe the learning never stops.

Wednesday, April 21, 2010

4/21/2010 Euthanasia

 Vet tip of the Day: Thinking about Euthanasia
I would like to introduce the topic of euthanasia with a few stories.  The first is one about an experience I had as a resident, and the second is about PipSqueak, a wonderful patient of mine

I completed a large animal internal medicine residency at the University of Georgia School of Veterinary Medicine.  I was on call to receive emergency patients into the hospital every 3rd weeknight and every other weekend for 5 consecutive years.  That's a lot of emergency admissions.  The sad reality of referral equine medicine is that we see a lot of very sick horses and many of them don't make it out of the hospital.

One weekend early in the first year of my residency I didn't sleep for 48 hours.  During that time I received 8 emergency patients.  Four of them were critically ill and over the course of two days I administered a lethal dose of sodium pentobarbital (euthanasia) to all four when it became clear that they had no hope of survival. Right there you come up against one of the more difficult concepts in the decision for euthanasia: no hope.  We all know that there always is hope, we just choose under certain circumstances to consider that hope too small to warrant the continued suffering of the really sick or the really old.  And let's face it, economic concerns and practical concerns influence the decision to end animal's lives as well.

That particular weekend in 1989 when I was a resident was very difficult for me. In the five subsequent years I never had to face the death of some many horses in such a short period of time.  I was exhausted, I was a new resident and I didn't have a lot of experience coping with the grief, guilt and confusion often experienced by owners when making the decision for euthanasia of an animal they love. At that stage of my career I also didn't have a lot of experience pushing the plunger on the syringe of "blue juice" that ends an animal's life.  I don't really remember all the details of that weekend.  I do remember that moment, just before performing each injection, when I wondered if perhaps there was hope, if perhaps I had misinformed the clients, if in fact the horse might survive if I could just do one more thing to turn its condition around, if I was making a terrible mistake.  None of these things was true, but the thoughts ran through my head nevertheless.  And I remember on Sunday afternoon, after I had humanely destroyed the fourth horse, sitting on the floor of the recovery stall outside the equine surgery suite and thinking, if one more horse comes in and requires euthanasia before tomorrow morning, someone else is going to have to push the plunger, I just can't take any more life today.

The second story is about PipSqueak.  PipSqueak was a grey arabian gelding who I took care of for 13 years, from the time he was 14 until his death.  Over these years PipSqueak belonged to 4 different owners, all of whom he taught the skill of riding after hounds, or foxhunting.  PipSqueak was a remarkable horse, an outstanding athlete, and a very wise soul.  Toward the last years of his life he was retired and turned out to pasture by his then owner.  His care was not adequate and he lost weight and began to have trouble getting up.  One of his previous owners, who by now was a teenage girl, saw PipSqueak's condition and reclaimed him.  She had owned PipSqueak when she was 8-12 years old and had ridden him all over the desert of Northern Nevada.  Now 15 years old, she brought PipSqueak home and fattened him up and took great care of him for another 9 months.

Although he was back in great body condition, PipSqueak's degenerative joint disease progressed to the point that he sometimes struggled for as long as 20 minutes attempting to rise, raising himself on his front legs but unable to lift his hind end to a standing position.  He was treated with joint supplements and anti-inflammatories, his hocks were injected, he was put on special footing and had special foot care, but his condition continued to deteriorate.  Finally his owner's grandmother called me one day to schedule an appointment for PipSqueak's elective euthanasia.

I arrived at the appointed time to find the entire family waiting with PipSqueak.  The horse had been bathed, his mane and tail brushed to a shimmering white, hoof dressing applied to all four feet, and he wore a beautiful new halter.  We all walked out with PipSqueak to the area where he was to be buried.  PipSqueak walked comfortably because his owner had given him one last whopping dose of bute that morning along with a bucket of grain so that he would be comfortable and feel especially spoiled in his final hours.  As we walked we shared stories of PipSqeak's many exploits over the years.

PipSqueak stood patiently while everyone said their goodbyes.  As I injected the sodium pentobarbital PipSqueak's family stood close by, speaking to him gently.  As soon as he fell to the ground we followed his descent, everyone keeping a hand somewhere on his neck or head.  We were very quiet,  his young owner began to cry and arms encircled her in her grief.  PipSqueak passed from life to death very swiftly, in the company of humans who loved and respected him, and who took the responsibility of ending his life squarely on their own shoulders, with compassion and grace.

I find the topic of euthanasia very complex, and will discuss it in more theoretical, and practical terms, over the next few days.  Please feel free to comment on this blog entry with your own thoughts and experiences concerning this topic.

I believe that education is the key to evolution.
I believe that learning never stops.

Tuesday, April 20, 2010

4/20/2010 Spring Breeding - the Transitional Period

Vet tip of the Day: The Mare's Transitional Period

It's the time of year when I get lots of calls regarding breeding mares.  In the past week I've also had several  about performance mares exhibiting unusual behavior and brood mares showing irregular heat cycles.  Both of these problems are related to the seasonal nature of mare's reproductive cycle, and may be particularly evident this year because of our unusual weather patterns. Today I am going to briefly review the mare's estrous cycle with emphasis on the transitional period that affects many mare's between January and April.

Seasonal variation in the duration of daylight has a profound influence on mare reproductive performance.  The horse is a seasonal breeder - increasing daylight improves the mare's reproductive efficiency while shortened days results in poor reproductive regulation.  Daylight is believed to act by stimulating the production of melatonin by the pineal gland, located within the brain.  This melatonin in turn causes the hypothalamus to release GnRH (gonadotropin releasing hormone).  GnRH acts on the pituitary, causing production of FSH (follicle stimulating hormone) and LH (luteinizing hormone) which influence the ovaries to develop and release follicles. In order for successful conception to occur, a mature follicle, or egg, must be fertilized by healthy sperm and then arrive in a uterus which is ready to accept and nourish it as it develops into a budding embryo. 

The transition from the short days of winter when most mares stop cycling all together, to the long days of June, when fertility is at its highest, is a gradual, progressive process.  During the spring and fall, mares enter a period of anovulatory receptivity, or the transitional period.  At this time, they often exhibit erratic estrus behavior, and while they appear to be in standing heat and accept a stallion, there often is not an associated ovulation of a mature follicle.  Even if a transitional mare does ovulate appropriately, it is also likely that the hormonal sequence necessary to maintain the early critical days of pregnancy will not be in place and the conceptus is lost.  Particularly in the spring, this transitional period is characterized by long, erratic heat cycles without ovulation. 

During the transition period performance horses often exhibit irritable behavior and are difficult to train.  It is during this time that trainers are often looking for ways to suppress reproductive activity so that their mares will behave appropriately in the show ring.  There are many oral supplements available over the counter which claim to improve the demeanor of irritable mares. The effectiveness of these supplements is debatable.  The only way to know if one will help your cranky mare is to try.  For years people have used cattle subcutaneous hormonal implants to control mare's heat cycles, but multiple research trials have been performed using these implants and no one has ever been able to show that they have any real effect on the mare's hormonal regulation.  Injectable progesterone in olive oil can be used intramuscularly to prevent mare's from cycling during the transitional period with variable success.  The only truly reliable means of controlling a mare's reproductive system and preventing cycling is the daily administration of  oral Regumate liquid (a synthetic progesterone).

Once the transitional period is over and mare's are cycling regularly, reproductive efficiency rapidly improves.  The "normal" mare has a 21 day heat cycle.  She is not receptive for 14-15 days (diestrus), then comes into heat for 4-7 days (estrus), ovulating 12-24 hours before behavioral signs of estrus disappear. Regarding performance horses, some mares continue to be difficult during the days close to ovulation, but in general the number of days when undesirable behavior is exhibited are markedly reduced, and can be predicted based on following the heat cycle.

So, when your mare is acting like a maniac and its February or March, remember that part of her behavior may be attributed to the "raging hormone" condition that we all recognize in each other from time to time.  Mares, just like people, are very individual in their reaction to their own internal chemistry.  Some have placid dispositions and do not seem affected by the ups and downs of hormonal transitions while others are truly distressed during these transitional phases and should not be punished when they are at the mercy of Mother Nature's nasty tricks.  If you own a mare you are trying to breed in the early spring, or a performance horse with seasonal behavior problems, speak with your veterinarian about management practices that may improve your breeding success or help your mare's disposition. 

I believe that education is the key to evolution.
I believe that animals are the key to compassion.
I believe the learning never stops.

Saturday, April 17, 2010

Prepurchase Exam III: Diagnostic tests

Vet tip of the Day: Prepurchase Part III - Additional Diagnostics
Key Words: Radiographs, ultrasound, endoscopy, blood work 

Today we will discuss the final aspect of a prepurchase examination: the decision to pursue further diagnostic tests.  Radiographs are commonly utilized to aid the veterinarian's evaluation of your prospective purchase.  In some cases, ultrasound, upper airway endoscopy, and blood work also may come into play.  Let's look at each individually.

There are two reasons to take x-rays.  First, to obtain further information about a specific anatomic region because of abnormal findings during the clinical portion of the exam.  A very common example would be a horse demonstrating a mild to moderate positive response to upper hind limb flexion, but no other signs of lameness.  Degenerative joint disease (djd) of the lower hock joints is very common in athletic horses (search blog entries for "hock" to review this subject) and often is quite manageable with appropriate medical therapy.  Therefore, hock radiographs are one of the most commonly obtained diagnostic series during prepurchase exams.

The second reason to obtain radiographs of the horse you are considering is to look proactively for radiographic abnormalities which may cause lameness problems in the future, or affect your ability to resell this horse, even though they are not causing clinical problems at this time. The most common anatomic areas investigated for these reasons are feet and stifles, but may also include fetlocks and carpi (front knees).

So how do you decide whether to request radiographs?  If your intended use for your new horse is pleasure riding or light competition, the horse is in full work and has a complete history, and the clinical examination of the horse is normal, you may choose to forego radiographic evaluation.  On the other hand, if you are buying a high level performance horse, if you are planning to re-sell the horse in the near future, if the horse has not been in full work prior to the prepurchase evaluation, or if there are any questions which arise after the horse's clinical evaluation, then you should seriously consider additional diagnostic tests based on consultation with the veterinarian conducting the examination.

One final word on radiographs: they sometimes open a can of worms that may be confusing to you.  While some radiographic abnormalities are straightforward, many are open to various interpretations.  If the horse you are looking at has abnormal radiographic findings in the absence of a corresponding clinical unsoundness, the veterinarian must give you their best professional opinion on the significance of the x-ray findings, but remember: they don't have a crystal ball! Once again, this brings up the importance of having a good performance record on your prospective purchase to help the veterinarian performing the evaluation interpret the significance of radiographic findings.

Ultrasound of the soft tissues of the distal limb, specifically suspensory ligament, superficial and deep flexor tendons, may be considered in higher level performance horses.  However, ultrasound imaging has not been standardized to the same extent as radiography, and ultrasound actually is not a sensitive tool for determining subtle changes in soft tissues.  I do not recommend ultrasound as part of a routine prepurchase examination.

Upper airway endoscopy usually is reserved for upper level performance horses such as race horses and upper level endurance horses.  During the exercise phase of the clinical evaluation, the veterinarian will ask the horse to canter long enough to elevate both heart rate and respiratory rate and will evaluate these systems immediately after exercise to look for any indication of upper airway problems indicating a need for endoscopic evaluation.

Blood work is not a bad idea.  Although very unusual, it is possible for a horse to be harboring a chronic inflammatory or infectious condition without showing outward clinical signs.  A complete blood count and chemistry screen can rule out the possibility of an underlying problem.  A toxicology screen testing for sedatives, analgesics (pain killers), or other behavior modifying drugs may be indicated in certain situations.  If you request a "tox" screen, be sure to ask the veterinarian what how long it will take to get results of this test - it may be up to a week, and thus you must factor this delay into your negotiation with the seller.

So that's the story on prepurchase examinations.  I strongly recommend you have a veterinarian conduct at least a full physical examination and basic lameness evaluation on any horse you plan to purchase.  There are  many problems that may not be apparent to either the seller or buyer that a vet can identify for you and help you understand before you make the decision to bring a new horse into your life.

I believe that education is the key to evolution.
I believe that animals are the key to compassion.
I believe the learning never stops.

Friday, April 16, 2010

4/16/2010 Prepurchase Exam II

Vet tip of the Day: What to Expect in Your Prepurchase Exam 
Key Words: Lameness, Conformation, Physical Examination, Suitability

Before I begin, let me apologize for the gap in my blog entries.  Spring is here and as much as I enjoy writing, my clinical practice takes first priority and it has been consuming my energy lately.  Also, in all honesty, I've been focusing on my young jumper in preparation for his first horse show of the season, and putting him ahead of writing time as well over the past week.

Back to the prepurchase exam.  What should you expect to see happen when a veterinarian is evaluating a horse for you?  First, a complete physical examination from head to toe, including an eye exam with ophthalmascope, careful ausculatation of heart, lungs and gastrointestinal tract with a stethoscope, a brief oral exam and careful palpation of the entire horse will  take place. We are mentally running through a check list of body systems as we perform this initial examination.  Before diving into the musculoskeletal portion of the examination we are checking skin, lymph nodes, circulation, heart and lungs, intestinal tract.  We get a sense of the horse's systemic well-being based on heart rate, respiratory rate, rectal temperature, body condition, and oral mucous membrane color and moisture.  Having completed the overall systemic exam, the musculoskeletal portion of the exam begins.

The veterinarian will look at the horse carefully from front, back and each side before beginning the hands on exam.The horse will be examined for conformational defects, musculoskeletal symmetry, body condition and mobility of large muscle groups such as the neck and back.  Each limb will be carefully palpated and manipulated and hoof testers applied to the feet.  As we feel each limb, there are specific anatomic structures being evaluated systematically by palpation and visual assessment.  Each joint is assessed for fluid filling and mobility.  Tendons and ligaments are palpated for painful responses and palpable swellings or irregularities.    After a thorough examination of the horse at rest, he will be observed in motion.

The gait evaluation portion of the examination will vary depending on the intended use of the horse, the horse's age and training, and the facility where the exam takes place.  For performance horses, even lower level athletes, minimum evaluation includes observation on a longe line at walk, trot and canter on at least two surfaces: once in deeper footing and once on hard ground.  In some cases the horse will be observed under saddle as well.  After evaluating the horse on the longe line it will be observed in hand at a walk and trot in a straight line.  Various full limb flexion tests will be performed to see whether these stress tests produce any alteration in the horse's gait.

Flexion tests are theoretically intended to reveal subtle discomfort in joints or soft tissue structures (tendons & ligaments) that may not cause overt lameness at the time of the examination.  When a horse trots off lame after a flexion test, it may indicate the need for further diagnostic evaluation such as radiographs (x-ray) or ultrasound.  The interpretation of flexion tests is controversial.  There is considerable debate among veterinarians concerning the significance of flexion tests.  The problem is the wide variation from horse to horse in the response to flexion and variations of technique in performing flexion tests between veterinarians.  This is one of the many areas where an experienced trainer, and a veterinarian you know and trust, can be of great assistance in helping you interpret the findings of a prepurchase examination.

I put a lot of effort into trying to make explanations of my findings clear yet thorough when speaking to a prospective buyer during a prepurchase exam.  However, I'll be honest with you,  it is challenging to condense years of knowledge and experience of the anatomy, pathophysiology, and demands of a performance horse's life into simple formulas that adequately explain the implications of every abnormality revealed during a prepurchase examination.  And that is what we are trying to do, both for the benefit of the buyer and the horse.  Therefore, it is important that you ask questions until you feel comfortable in your understanding of the significance of the veterinarian's findings with respect to YOUR needs for THIS particular horse.  Finally, you must understand that as veterinarians, we are asked to look at a horse once, over the course of 45 minutes to a couple of hours, and determine whether it is going to stay sound and healthy for years to come.  Obviously this isn't possible, but remember from the last blog post, you are most likely to have a positive outcome if the horse you are looking at has a complete history and is in full work at a performance level close to its intended use for you.

In tomorrow's blog (and I PROMISE to write an entry tomorrow) we will discuss ancillary tests, such as x-rays, ultrasound, and blood work which may be part of your pre-purchase examination.  Until then, enjoy the sunshine and warmer weather!

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I believe that education is the key to evolution.
I believe that animals are the key to compassion.
I believe the learning never stops.

Friday, April 2, 2010

4/2/2010 - The Prepurchase Exam

Vet tip of the Day: The Prepurchase Examination
Key Words: Intended Use, Physical examination, X-rays
 Today I am going to discuss some theoretical considerations regarding prepurchase examinations.  Tomorrow I will go over the nuts and bolts of the prepurchase exam including what you should expect your veterinarian to do during the exam, and how to determine if x-rays or blood work are indicated.  Right now let's begin with a look at the issue of suitability.

Today I completed a prepurchase examination on a 15 year old arabian endurance horse.  The horse was experienced, with 5,000 competition miles and no history of lameness problems.  The buyers were looking for a safe, experienced horse to do 25 to 50  mile endurance rides, but not at a highly competitive level.  The horse had not been competing for the past two years, but had been consistently ridden as an athletic trail horse.

I share this information with you, and chose this picture of the little cowgirl riding her barrel patterns on what appears to be a very wise old mare, for a reason.  The arabian gelding I saw today, and the old quarter horse poking around the barrel are two very different horses, but each is appropriate for their rider's needs.

A prepurchase exam is a veterinarian's evaluation of a horse's physical well being based on a single evaluation which takes from 45 minutes to a couple of hours to complete. While a tremendous amount of valuable information can be gathered based on a thorough physical examination, lameness evaluation, and diagnostic imaging, even the most rigorous prepurchase exam cannot replace a good history on a horse's past performance record and a buyer's solid understanding of their goals in purchasing this horse.  Obviously the little cowgirl's horse needn't demonstrate the same athletic ability as the 15 year old endurance horse.

As a veterinarian, one of the most challenging situations when performing a prepurchase examination is trying to evaluate a horse with an unknown history which is not performing the job for which it is intended.  For example, last fall I was asked to evaluate a 9 year old thoroughbred mare being purchased as a children's show jumper.  The mare had done some showing as a 5 and 6 year old, and then for an unknown reason had become a brood mare.  She had 2 foals then didn't conceive last year and now was for sale. 

Evaluating a horse like this is really difficult.  She has not been in any kind of exercise program for 3 years and there is no explanation for her change from performance horse to brood mare.  She may have a perfect prepurchase examination on the day I look at her.  She may be sound, have good conformation and pass all my flexion tests and limb palpations with flying colors.  She may have normal x-rays of her hocks, and front feet.  From my perspective, she is a sound horse.  However, I always caution buyers of such animals that the horse is not performing at the level of intended use and has an incomplete history therefore it is impossible for me to have great confidence in assessing the horse's long term prospects for continued soundness.   In fact, when this mare was put back in regular work and began jumping she developed a hind limb lameness that was attributed to a suspensory injury, which very possibly had been the reason she became a brood mare in the first place.

The moral of the story is this:  when purchasing a horse, always look for an animal that is in work, and performing at least close to the level at which you intend to use it.  It is then much more likely that your veterinarian will be able to accurately identify issues of concern and discuss them with you.  Make every effort to obtain a history of the horse's past performance and ask the seller why the horse is for sale.

A prepurchase examination is a very important part of making a wise investment.  Often I identify problems during a prepurchase exam about which the seller was unaware - that is why we subject the horse to unusually rigorous conditions during the examination such as trotting small circles on very hard and very soft surfaces.  But at the end of the day, the ethical horse seller with a complete history on their horse can be equally as valuable as your veterinarian's assessment.  Tomorrow I will discuss in detail what you should expect from your veterinarian during a prepurchase examination.

The wind is howling - Mother Nature has been very restless throughout March and appears to be continuing her mood right into April.  Keep your head down and your spirits high.

Thursday, April 1, 2010

4/1/2010 Protecting our Ecology

Vet tip of the Day: Homeostasis- Support the Water Wars
Today's vet tip isn't strictly about veterinary medicine, but it is about the most important concept behind practicing good medicine: Homeostasis.

Whenever I am treating a very sick horse, foremost in my mind is the concept of homeostasis, which is the natural balance of all the elements in the body which when present, produces a healthy organism.

This morning I received a call from a client who has been deeply involved in a fight in the area where I live to stop the exportation of dangerous amounts of water out of our delicate watershed by a land development consortium.  She asked me to post the following message on the blog on behalf of the Northern Nevada Citizens for Water Conservation.  For many of us, riding our horses in the exquisite high desert environment of Northern Nevada nourishes our souls in a manner that defies expression.  The exportation of water proposed by these developers threatens the homeostasis of this delicate ecological system.  Please read Helen's message and do anything you can to support NNCWC in their fight for our precious native ecology.

You are all probably aware that RRR LLC have filed an appeal to the

Nevada Supreme Court with regards to the Washoe County Commission's
decision not to allow them to export water from our valley.
RRR LLC has been denied this on three different occasions; at the
Community Advisory Board, Washoe County Commission, and most recently
in their request for a Judicial Review.
Northern Nevada Citizens for Water Conservation has organized and funded this
fight. We hired an attorney when the Judicial Review was requested, by
doing so we were allowed to have our testimony and concerns heard.
Legal fees have pretty much exhausted our funds. How far we have gotten
in our cause, on fundraisers and donations is remarkable.

NNCWC is working for everyone's water. We need money for round number
four, it's that simple. Please put your donation in perspective with
what you are at stake to lose; if your well levels drop and you are
forced to drill deeper, (hoping to find the diminishing water table);
how that will affect your property value or even your ability to
exist here...

One more thing, be aware that the State Water Engineer has been
severely chastised by the courts for allowing excessive water
exportation permits to the potential devastation of environments and
small rural communities. The message being that their interests are not
necessarily yours, nor are they looking out for you. Please help. Send
contributions to: NNCWC 448 Hill St Reno, Nv 89501.

To learn more about water issues in the West, log on to

Thank you,
Helen Mooney

Wednesday, March 31, 2010

3/31/2010 - Vaccination Reactions II

Vet tip of the Day: "Allergic" reactions to vaccination
Key Words: Urticaria, hives, hypersensitivity, anaphylaxis

Most importantly, remember that severe vaccination reactions are rare.  That's why it was difficult to find a decent picture - sorry for the quality of this one.  True hypersensitivity or anaphylactic reactions to vaccines, while rare, do occur and require immediate attention.  The physiology behind these reactions is very complex and poorly understood in horses. 

Anaphylaxis refers to a shock reaction by the body to some foreign substance.  In the case of vaccines, anaphylaxis can occur the first time a vaccine is administered.  An anaphylactic response can vary from mild hives that appear hours after a vaccine is given, to acute life-threatening cardiovascular collapse which can occur within minutes of vaccination.  Epinephrine is the preferrred initial treatment for severe anaphylasis.  It works by counteracting the immediately life-threatening components of the body's severe inflammatory response.  It is usually administered by intramuscular injection.  In the most severe cases, it may be given intravenously.  Administration may be repeated every 15-20  minutes if necessary.

Hypersensitivity and immune-mediated reactions to vaccines also occur and may have similar clinical signs to anaphylaxis.  When these reactions occur, they usually are less dramatic than acute, severe anaphylaxis.  Signs may include swelling of the muzzle, face and throat region, which can lead to respiratory distress, or may manifest as hives, or urticaria.  Depending on the severity and progression of the clinical signs, treatment may include steroidal or non-steroidal (phenylbutazone, flunixin/banamine) anti-inflammtory agents, and/or anti-histamines.

When a horse experiences an adverse reaction to vaccination, the question always arises, should the horse be vaccinated again?  If the reaction is a very sore neck, sometimes changing vaccine brands, and thus the adjuvant used, will help.  If the horse has a true anaphylactic or severe hypersensitivity response to vaccination, the problem is more complex and the decision to repeat vaccination should be made based on the severity of the reaction and consideration of the true risk of the disease against which vaccination is directed.

Finally, for those of you who adminster your own vaccines, be aware that storage conditions are extremely important for vaccines.  Vaccines that are not stored at proper temperatures are significantly more likely to cause adverse reactions than those kept cool at all times. Also, correct administration of intramuscular shots, both with respect to location of the injection and injection technique, play important roles in the safety of injections.  If you choose to vaccinate your own horses, be sure to obtain instruction from a licensed veterinarian or licensed veterinary technician concerning the correct administration of intramuscular injections.  And be sure that your vaccines have been properly stored before you purchase them, check the expiration date, and keep them carefully stored until they are administered.  Better yet, take advantage of the chance to visit with your vet and have a spring wellness check up and make an appointment with your veterinarian to give your spring vaccinations!

It's cold and snowy on March 31 in Northern Nevada.  What's it like where you are?  Looking forward to spring and good riding weather.

Tuesday, March 30, 2010

03/30/2004 - Vaccination Reactions

Vet tip of the Day: When Vaccinations go Wrong
Key Words: Vaccine, adjuvant, immune system, clostridium

Vaccination season is drawing to a close, but I thought I would return to this subject one more time to talk about vaccination reactions.  Of course I would like to tell you that I have never had a horse demonstrate an adverse response to vaccination, but that would be a big fat lie.  Fortunately, I can tell you that I have never had a horse suffer a serious vaccination reaction that didn't respond promptly to appropriate treatment. There are several types of adverse reactions to vaccination, and it is important that you understand how they differ, both in onset of signs, and seriousness of consequences.

By far the most common adverse reaction to vaccination is the simple sore neck.  I vaccinate hundreds (literally) of horses every spring, and this year to date I know of only two horses which developed significant signs of neck pain following vaccination.  Typically the day after vaccination the owner notices that these horses are unwilling to move their heads, show signs of pain if one of the vaccination sites is touched, and exhibit swelling at the vaccination site.  Occasionally the discomfort will be so severe that horses will not lower their heads to eat or drink, or will pull back if pressure is applied to a lead rope when they are haltered.  Years ago I had a client call to tell me that her horse was having a seizure when in fact the horse's neck was so painful that when the owner tried to lead her forward she reared over backwards in response to the pain.  The vast majority of inflammatory reactions after vaccination resolve within 48 - 72 hours with palliative therapy including warm compresses and phenylbutazone.

This "sore neck" reaction to vaccination is NOT an allergic response to the vaccine.  It is an exagerrated inflammatory response to the ingredient in the vaccine that stimulates the horse's immune system.  This ingredient is called an adjuvant, and is very important in causing vaccines to elicit a strong antibody response by your horse's immune system.  Without this response, the vaccine will not be effective in preventing the disease against which it is directed.  Drug companies spend a lot of time and money developing different adjuvants.  Their goal is to find an adjuvant that is a potent stimulator of the immune system but does not cause severe local soreness.  Over the years I have used many brands of vaccines, and have come to be a staunch supporter of Intervet vaccines.  I believe that their adjuvant causes very few advers reactions, and I have been impressed with the company's dedication to client education and with their committment to research and development of new products to protect horses' health, such as Prevenile, their DNA based West Nile vaccine.

When a horse develops a sore neck after vaccination, it is important to notice whether or not the horse is systemically ill.  Specifically, will the horse refuse food and water even when it is placed so that the horse can reach it without lowering its head? Is the horse's temperature over 102.5 degrees?  Is the swelling at the vaccination site severe and increasing over time?  When the swelling is palpated, is there a crackling feeling underneath the skin?  Does the horse appear markedly depressed?  If the answer to any of these questions is yes, then the horse should be examined by a veterinarian.  As stated earlier, the vast majority of inflammatory reactions after vaccination are not serious and resolve within 48 - 72 hours with palliative therapy including warm compresses and  phenylbutazone.  However, in rare cases, it is possible for a bacteria called Clostridium to grow deep in muscle tissue at a vaccination site. If this unlikely event does occur, it can be life-threatening.
Clostridial bacteria exist normally in the environment in a spore form which can only grow in the abscence of oxygen.  Even when a clean needle and syringe are used and the vaccination is administered correctly, it is possible for Clostridial spore sitting on the skin to be carried deep into the muscle tissue by the needle during vaccination.  When this happens it is a random, extremely unlucky event, and does not mean that the vaccine was administered improperly.  Clostridial infections can be life threatening and require prompt and aggressive treatment. The Clostridium bacteria grow rapidly in the abscence of oxygen and produce several toxins which invade the horse's blood stream and cause severe systemic illness which can be fatal. Therefore, it is always a good idea to contact your veterinarian if your horse has an adverse reaction to a vaccine and discuss your horse's specific clinical signs so that you and your vet can decide if your horse needs to be examined.  If you take your horse's temperature and do a physical examination (see blog on this!) and carefully observe your horse's behavior before you call your vet you will be best able to provide important information in making that decision.

In tomorrow's Vet tip of the Day I will discuss Allergic reactions to vaccination and the importance of careful storage and administration of  vaccines, for those of you who vaccinate your own horses.

Until then,

I believe that education is the key to evolution.
I believe that animals are the key to compassion.
I believe the learning never stops.

Thursday, March 25, 2010

4/25/2010 - How Diseases Spread

Vet tip of the Day: Infectious Disease Control/Equine Herpes Virus
Key Words: EHV-1, EHV-4, neurologic disease, upper respiratory virus

This story is loosely based on actual events that took place in 2007-2008, spanning from Europe to New York, then south to Florida, and west to California. The goal is not to alarm you, or make you an expert on Equine Herpes Virus type-1 (EHV-1), but to provide guidelines on how to protect your horse from infectious diseases. Developing an increased awareness of how diseases can change and spread rapidly will help you to improve the care and well-being of your equine companions. Our story:

An eight-year-old horse that received excellent care in Germany was purchased by a person in the United States. He was vaccinated and dewormed regularly, and received appropriate booster vaccinations three weeks before his transport by air to New York. Upon arrival he was quarantined according to federal regulations. Once released from quarantine, he was transported by truck to Kentucky with one group of horses, and then shipped on to Florida with a different group. When he arrived in Florida 10 days after leaving New York, a handler noticed he seemed depressed and unsteady on his feet. The owner was alerted and a veterinarian was contacted to evaluate the horse.

How are diseases spread?

How and why did the horse become ill? We know the horse received excellent management with booster vaccinations for appropriate infectious diseases three weeks before shipping overseas. The immune system takes at least 10 days to fully respond to a booster vaccine, so ideally they should be given two to four weeks before shipping or change of environment.

It would have been advisable to rest the horse in New York following the flight and quarantine before transporting to Florida, and to avoid the mixing of different groups of horses during travel. Research has shown that horses subjected to long-distance transport are at significantly greater risk of infection with respiratory tract pathogens compared to similar non-transported horses.

The veterinarian exam revealed the horse had a 102.5 ºF fever and neurologic signs manifested as weakness and incoordination of the hind limbs, and a rectal palpation determined the horse’s bladder was distended with urine. The owner was told that a neurologic form of EHV-1 was suspected and immediate isolation was recommended until a diagnosis could be confirmed because a new, highly contagious form of this disease had been reported in other U.S. locations.

What is EHV-1?

Equine Herpes Virus Type-1 (EHV-1) is an old and common disease in horses, most commonly causing an upper respiratory infection in young horses, but also responsible for late term abortion and a sporadic neurologic disease. Luckily, this veterinarian was aware of outbreaks in recent years of neurologic disease affecting multiple horses caused by EHV-1; most notably one in a university hospital in which 46 of 135 in-house patients developed neurologic signs, leading to death in 12 of those horses.

It was discovered that the EHV-1 virus had undergone a mutation in which a single element in the viral DNA code was altered. The resulting strain was more virulent, contagious, and specifically attacked the horse’s neurologic system. Therefore it was named neuropathogenic EHV-1. With the emergence of this mutated virus, the clinical form of EHV-1 associated with neurologic signs was becoming more common and more. This exemplifies how a tiny change in the genetic code of a virus can have far-reaching and dangerous effects.

In Florida, a nasal swab confirmed the diagnosis of neuropathogenic EHV-1. This first horse was treated and recovered. Meanwhile, another horse off-loaded from the original truck in Kentucky was arriving in Southern California, and a third horse that had accompanied our horse by van to Florida was taken to a farm, and later to a horse show facility nearby. The horse in California walked off the truck with clinical signs similar to the first index horse in Florida, and was quickly assessed and isolated. The third horse never showed signs of illness, but 10 days after arriving at the show grounds, other horses began to develop signs of neurologic disease. Subsequently, the presence of the neuropathogenic form of EHV-1 was confirmed, leading to an extended quarantine of the show grounds. No other cases were detected in Southern California after isolation of the index case, but within the month, a horse was confirmed infected at Golden Gate Race Track. There have been isolated confirmations of neuropathogenic EHV-1 in California horses since, but no multiple case outbreaks have occurred.

Disease control and prevention among horses

How could the spread to the show grounds have been prevented? First, when a contagious disease is suspected, the affected horse should be isolated and other in-contact horses should be quarantined and monitored for signs of disease for an appropriate duration. This would have meant immediately contacting the shipping company and identifying all the horses transported with the original horse in Florida with clinical signs. In the case of EHV-1, the incubation period is typically two to eight days, but can be as short as 24 hours – showing how quickly this becomes a logistical nightmare, and how critical every hour becomes. The horse in Southern California was traced back to the horse in Florida, which was connected to the air transport from Europe – tedious tracking, but important to successfully contain infectious diseases.

Second, rapid diagnosis is critical. Our astute veterinarian in Florida submitted the nasal swab for a state-of-the-art diagnostic technique called PCR (polymerase chain reaction). This test amplifies specific DNA segments in the sample and allows the detection and identification of minute amounts of viral DNA, confirming that this particular viral strain was present in the affected horse.

Finally, how can you as a horse owner reduce the spread of infectious disease? Your first goal is to protect your horse against infection by consulting with your veterinarian to ensure that your horse is appropriately vaccinated. Learn all you can about the safe and comfortable transporting of horses. With these good management techniques, you’re supporting your horse’s immune system and reducing the odds that he will succumb to an infectious disease, even in the face of exposure. Use common sense during competitive events: do not share water, tack, or grooming equipment. EHV-1 is spread primarily by horse to horse contact and by virus transported on equipment and the clothing, hands, and shoes of people moving between horses. If your horse is exposed to fewer viral particles and has a healthy immune system, illness is less likely.

When your horse is at high risk of contracting an infectious disease such as EHV-1, even the best management may not protect him completely. If he does become infected with a contagious disease, your goal is to protect him and other horses with early detection. Fever is the earliest sign of most viral diseases. The single most important thing you can do is to monitor your horse’s rectal temperature twice daily at shows, before and after shipping, and when new horses come on the property. Whenever your horse’s rectal temperature is 102.2 ºF or higher, contact your veterinarian and follow their recommendations.

Don’t abandon your equestrian activities for fear of infectious disease. Just stay informed and use common sense to guide you. Your veterinarian is your best resource for advice on the prevention and control of infectious diseases. Don’t hesitate to ask questions and continue your life-long education as a responsible and caring horse owner.

More Information on EHV-1

This story first appeared in Petfolio magazine, published in Reno, Nevada.

I believe that education is the key to evolution.
I believe that animals are the key to compassion.
I believe the learning never stops.

Wednesday, March 24, 2010

3/24/2010 Normal Physical Exam

Vet tip of the Day: The Normal Horse
Key Words: Heart rate, Respiratory Rate, Temp, Gut sounds, mucous membranes

I performed a prepurchase examination for a new horse owner this week.  She had lots of good questions about her horse husbandry.  One thing she was interested in was learning normal physical examination findings, so I thought I would go over some basics which all horse owners should know.  In case of emergency, or if your horse simply isn't feeling well, being able to do a basic asssessment of your horse's physical parameters can be extremely useful.  Not only does it give you factual information to convey to your veterinarian over the telephone, it also gives YOU factual information to allow you to determine just how serious your horse's condition may be.

First you need some equipment.  Go to any nursing supply store and by a CHEAP stethoscope.  The most basic model is perfectly adequate for obtaining a heart rate.  To listen to your horse's heart, place the flat side of the stethoscope bell against your horse's chest just behind the point of the elbow, then push the stethoscope head forward as far as you can so it slides in underneath the triceps muscle.  Close your eyes and listen carefully.  The heart beat has two parts - lubdub...lubdub...lubdub.  Practice until you can hear it clearly.

Next go to the drug store and buy a regular old human digital thermometer - I prefer the non-flexible ones. 

Finally, purchase a small, LED flashlight and cheap watch with a second hand and store them, along with your stethoscope, thermometer, and a small notebook with a pen attached to it by a piece of string in a handy place in your feed or tack room or horse trailer.

Here are some normal numbers - write them down in your notebook so in an emergency you don't have to remember them. 

Heart rate: 28- 44 beats per minute.  I usually count the heart rate for 15 seconds and multiply by 4 to get beats/minute. Heart rates over 52 beats per minute are definitely abnormal.  Heart rates over 80 beats per minute indicate severe cardiovascular distress.  Remember, exercise, nervousness or excitement may cause your horse's heart rate to be elevated without any serious illness present.
Respiratory rate: 8-16 breaths per minute.  The best way to count the respiratory rate is to stand back from the horse and watch the abdomen just behind the ribcage.  In a normal horse you will see a gentle rise of the abdomen with each breath.  Taking an accurate resting respiratory rate in a normal horse can be difficult, because as soon as you approach them they begin sniffing and snuffling, thereby disrupting the quiet, resting breathing rate.  If your horse has a wide flare to the nostrils with each breath and an deep movement of the abdomen with each breath coinciding with the nostril flare, this is a sign of labored breathing and is abnormal.
Gut Sounds: Using your stethoscope, listen to your horse's abdomen in 4 places - up high and down low on each side, behind the ribs and in front of the hip.  Gut sounds vary tremendously even in a normal horse, but if you listen for 30 seconds in each location, you should hear at least one good, rumbling gurgle in each of your 4 listening zones.
Mucous membranes: Standing beside your horse's head (not in front), lift your horse's lip just enough to see the gums above the incisors on one side.  Normal gums are quite pale pink, with a glistening surface.  If you press against the gums firmly with your finger for a few seconds, when you remove your finger the gums should be white, and should refill with the normal pale pink color in less than 2 seconds.  This is called the capillary refill time (crt).
Attitude:  When I record my physical examination findings, I will often note: BAR.  This is code for Bright, Alert, and Responsive.  When you do your physical exam, note your horse's attitude, expression, head position and body position. Look in the stall or pen and check for fresh manure, or signs of distress such as areas where your horse may have been pawing or rolling.  Check to see if the water trough is full and if the last feeding has been consumed.
Gait/Posture:  Finally, move your horse around a bit and check for lameness and willingness to move forward.

Now you are prepared to do a comprehensive physical examination on your horse.  The best way to recognize abnormal is to know normal, so practice performing physical examinations on your horse frequently so that when you are concerned that something isn't right, you will be confident in your assessment.


Sunday, March 21, 2010

3/28/2010: More on Vaccines

Vet Tip of the Day: Vaccinating old horses
Key Words:  geriatric, immune system
A client called this week asking about recommendations for vaccinating old horses and mules.  She was wondering if her old retirees still needed all the same vaccinations that her younger, active, travelling horses receive.  I thought I would answer her question with a blog post so you could all share this information.  Please first review the two previous blog entries on vaccinations posted earlier this spring.  To find them you can type  - vaccination - into the search bar at the top of the blog home page  OR click on - vaccination - in the label group in the top left margin on the blog home page.
Let me reiterate that the decision to vaccinate any horse should be made based on an assessment of risk of disease to that horse and to the other horses in that horse's population group.  With this in mind, let's look at the geriatric horse in particular.  Your old horse's immune system is likely to look pretty much like your old horse does: it ages along with the rest of his body, inside and out.  When deciding whether or not to vaccinate the old fellow, consider the following: his body condition, his mobility, and his population dynamics.  Then think about each disease against with we vaccinate in the terms discussed in the previous blog posts.
Let's consider a contagious disease (spread from horse to horse) such as the upper respiratory viruses - Flu/Rhino.  Keep in mind that immunity to these viruses in general is relatively short lived in all horses.  Should your old horse contract influenza it may take longer for him to recover, and, under certain circumstances he may be at greater risk of developing complications such as pneumonia.  What are these circumstances? Living as part of a  large group of horses in a small area is probably the most threatening to an old horse.  If your horse has chronic lameness issues that cause him to spend significant periods of time lying down, again he is at increased risk of  secondary pneumonia.  If your horse is in poor body condition or has poor dentition, he is at greater risk of having difficulty shaking the flu.  If, however, your retired horse or horses are in good health, living in a large field without much contact with other horses, then their liklihood of contracting a contagious disease such as influenza or rhinopneumonitis is decreased, and should they "catch a cold", it is likely it will run its course without complication.  Under these conditions, you may choose not to vaccinate against Influenza or Rhinopneumonitis.

Concerning Strangles (Strep Equi)  the situation is somewhat different.  While Strangles is a highly contagious disease spread from horse to horse, it also is a disease which causes a powerful and long-lasting immune response in those exposed to the disease.  Because Strangles is common in our area of northern Nevada, most older horses have good naturally aquired immunity.  Therefore, Strangles is uncommon in older horses.  Unfortunately,  old, debilitated horses which do contract Strangles are definitely at higher risk of potentially life threatening complications.  I recommend Stranges vaccination in old horses only if they are living in a high risk environment such as a concentrated boarding barn with high turnover of population or on a breeding farm with high number of foals in close contact.

All older horses should be vaccinated against West Nile Virus.  The disease is sporadic and unrelated to population dynamics.  To contract West Nile Virus, an infected bird flies over your horse's location, a mosquito bites the bird and within a short period of time that same mosquite flies down and bites your old horse.  Old horses definitely are at greater risk of death should they contract West Nile Virus.

Tetanus?  Sleeping Sickness?  The killed vaccines used against these diseases are very effective and afford long lasting immunity.  If you have owned your old friend for years and know for sure that annual tetanus/encephalitis vaccine has been administered, I would be comfortable decreasing the frequency of that vaccination to every 3 years rather than annually.  If you select this route, BE SURE that your horse receives a tetanus toxoid (not tetanus antitoxin) should he develop a foot abscess or deep puncture wound.

Hopefully this information will be of use to you when deciding which vaccines are appropriate for your old horses.

Forward this blog entry to all your friends with old horses.  Become a fan of HighDesertEquine on Facebook - and sign up as a follower of this blog! Your participation is vital to the success of these internet information efforts - every new fan and member moves us up on the search engine list and means that these educational articles will reach more people trying to become better informed caretakers to their horses. 

Wednesday, March 17, 2010

3/17/2010: New Foals Arriving!

Vet Tip of the Day: Keeping your Newborn Foal Healthy
Key Words: neonate, umbilicus, colostrum, IgG, plasma, passive transfer
It is spring, and for me that means lots of work related to reproduction.  Ironically, it seems like I'm either stopping reproduction (gelding colts) or enhancing reproduction (breeding mares) every day.  But the most fun for me is welcoming new equine lives into the world.

I strongly recommend that you look at the Mare & Foal page on our website (link at top of blog page).  There is an excellent revue of prepartions needed before your foal is born.  What I'd like to do  here is speak in a bit more depth about the equine neonate and its particular susceptibility to infection in the first few hours & days after birth.

Foals are born with naive immune systems.  This means that when they hit the ground, they have NO circulating antibodies.  Their bodies begin responding to challenges and producing antibodies immediately, but the development of a fully competent immune system takes time, and in the first hours and days of life an invading organism can quickly gain the upper hand.  Antibodies are the body's infantry in the fight against infection.  Without antibodies, we succumb to disease causing organisms and we die.  End of story.  No exceptions.  Foals obtain critical antibodies in colostrum, the first milk produced by their dams.  The absorption of colostral antibodies by the foal from the mare's milk is called passive transfer.  Two basic things have to happen for successful passive transfer to occur. 
1) The mare must be healthy and produce sufficient quantitiy and quality of colostrum.  Older mares, malnourished mares, and maiden mares all are at risk of producing poor quality colostrum.  The ideal high quality colostrum producer is a mare between 6-10 years of age, giving birth to her second foal, on an excellent diet, vaccinated 4-6 weeks before foaling to increase antibody production against common diseases
2) The foal must drink and abosrb the colostrum.  The antibodies in colostrum are very large molecules.  The foal is born with specialized cells in its small intestine which can absorb these antibody molecules.  These cells only function for 12-24 hours after the foal is born.  Therefore, the foal MUST consume adequate colostrum during the first 12 - 18 hours of life.  After this small window of opportunity closes, it doesn't matter how much colostrum the foal drinks, it will not be absorbed.

Sounds simple, but often it is not.  Maiden mares may be nervous about allowing foals to drink and they may have limited quantities of colostrum.  Foals born in severe cold may be slow to rise and may have delayed intestinal motility decreasing colostral absorption.  Foals born prematurely or with musculoskeletal abnormalities may also be slow to rise and nurse. All foals should be up and nursing within 2 hours.  If a foal is not nursing vigorously within 2 hours please contact your veterinarian immediately.  Foals are very delicate creatures and succumb rapidly to infections in the first few days of life, often with fatal consequences.

Let's assume your foal gets up and nurses appropriately and your mare has adequate colostrum.  Great! However, there are still risk factors which may predispose your foal to early infection.  The envivonment in which the foal is delivered should be clean and dry.  The foals' umbilicus is a little highway into the foal's blood stream for disease causing bacteria in the foal's environment.  The umbilicus should be dipped in 2% idodine or dilute chlorhexidine 3-4x in the first 24 hours of life to help minimize the chances of ascending infection through the umbilicus.

Even with successful passive transfer (absorption of colostral antibodies) if a foal is exposed to a large number of pathogenic (disease causing) bacteria in the first hours of life, they are at risk of developing a bactrial infection of the blood stream.  This is called neonatal septicemia, and is often fatal in foals.  The key to succeful treatment of neonatal septicemia is early detection and aggressive intervention. 

I cannot emphasize enough the importance of contacting your veterinarian IMMEDIATELY if any of the following is true:

Your foal is 2 hours old and is not up and nursing
Your foal shows signs of decreasing energy/lethary/depression at any time in the first week of life.
Your foal develops diarrhea.
Your foal shows signs of abdominal pain - foals with colic often roll up on their backs and lie like a dog with all 4 legs in the air, or they may roll and thrash like an adult horse with colic.
You notice that the mare's bag is full or is dripping milk and the foal is not nursing vigorously at least twice every hour.
You notice that your foal is constantly trying to nurse and does not lie down and sleep between nursing - this is hallmark sign that the mare does not have sufficient milk productio and the foal is hungry.

Please remember that foals are particularly delicate creatures - early intervention can often save them, but a delay of a few hours can mean the difference between life and death for a sick neonatal foal.

All foals should be examined by a veterinarian at 18-24 hours of age at which time a physical  examination and blood test to check for adequate colostral absorption is performed.

Don't be complacent about your newborn.  If you have any questions or concerns, call your veterinarian immediately - these precious lives are in our safekeeping, take the best care of them you possibly can.  Please read the mare/foal care information on our website.


Monday, March 15, 2010

3/14/2010 - Spring is Coming

Vet tip of the Day: Thinking about spring and your horse's feet
Wow, the sun came out and I wasn't wearing 4 layers today.  It was such a wonderful feeling not to feel that chill in my bones.  With spring come those freeze thaw cycles when the ground is frozen in sharp, uneven layers at night only to thaw and turn into a slippery slimey mess during the day.  For many of us our horse's turn out areas are a mess this time of year. Particularly around feeders and water troughs, footing tends to be wet during the day and frozen at night.

Because our soil is usually so dry, our horse's feet are adapted to a dry environment.  After a long wet winter as we've had this year, the manure and urine soaked into high traffic areas where horses stand a lot, combined with the freeze/thaw cycles, create a bad formula for our horses feet.  This time of year I see LOTS of severe subsolar abscesses, particularly in older horses.  Here's what happens: first, the horse living in a dry desert climate typically has a hard, somewhat brittle sole.  Over the winter, if the horse's environment is not kept clean and dry, then wet, manure packed material accumulates in the sole and along the sulci of the frog.  This material is full of bacteria.  It softens the frog which becomes recessed, thereby leaving the sole in direct contact with the ground.  The horse steps on a frozen jagged mud edge, creating a tiny defect in the sole which provides access for bacteria to infiltrate into the foot.  The bacteria become trapped beneath the hard sole where there is no air supply.  They begin to proliferate, spreading between the natural layers of the sole.  In response to the bacterial proliferation, the body mounts an inflammatory response, resulting in the accumulation of pus.  Eventually this pus produces enough pressure within the hoof that the horse becomes acutely severely lame.

At this point the sole must be removed to allow drainage of the dead tissue and expose the area to air.  In the worst case scenario, it is possible for the bacteria to migrate far enough into the hoof to cause infection of the coffin bone, although this is NOT the typical outcome.  Once the dead sole is removed exposing the area where the bacteria have infiltrated, with appropriate treatment the sole will harden and repair itself without long term complications.  However, subsolar abscesses are extremely painful, and can be frustrating and time consuming to treat, especially in horses living in outdoor settings.

Prevention is worth a pound of cure, and subsolar abscesses that occur secondary to poor footing conditions during the winter are preventable. First, be sure your horse has regular farrier care.  Second, PICK YOUR HORSES FEET OUT THOROUGHLY EVERY DAY!  Third, try to keep the area around feeders and water troughs as dry as possible, and remove manure from these areas.  If this is not possible,  using a tooth brush rub strong iodine (7%) into your horse's soles and frog several times a week after you clean out the feet.  Following these three simple rules may save you and your horse a major aggravation.  Again, this problem is especially prevalent in older, less active horses, so don't forget about the feet of the retirees, even though they are no longer performance horses.

Friday, March 12, 2010

3/12/2010 - Anatomy and OCD

Vet tip of the Day: Significance of OCD based on anatomic location
Key Words: Osteochondrosis, lameness, joint, anatomy

This cute foal picture is here to remind you that OCD is a developmental orthopedice disease.  In other words, it develops as a foal grows, although it may not manifest itself clinically until later in life when joints are subjected to the rigors of training and controlled exercise.  When we consider the prognosis of various OCD lesions, then, there is one common sense rule to keep in mind: foals that develop significant lameness early in life due to OCD are likely to have more severe lesions than animals that do not show any clinical signs until they are older and in training. 

Regardless of the anatomic location, the larger and deeper the OCD lesion is in a given animal, the less likely it is that surgical treatment will be successful.  In general, the degree of lameness and age at onset correlate with the severity of the lesion.  Consider our mare Classy, a five year old just completing 60 days of fairly rigorous training and only demonstrating a grade 1 lameness and mild joint swelling.  Even before examining her radiographs, one can be hopeful that her prognosis for full function would be favorable.  And this is in fact the case.  Classy has an excellent prognosis for a full athletic career following surgical debridement of her stifle lesions.  On the other hand, a 6 month old weanling with grade 3 lameness and severe swelling of the stifle joint undoubtedly has a more conservative prognosis for an athletic career, even with appropriate treatment.

OCD can occur in any joint in the body. The most commonly affected joints are the stifle, hock and fetlock, and less commonly the shoulder and cervical spine (neck).  Within each of these joints there are several locations where lesions can occur.  In addition, lesions may occur as mineralized cartilage fragments that have separated from the underlying bone (see Classy's x-ray's for a beautiful example) or they may appear as cyst-like lesions, where the cartilage lining the bone is still intact, but is no longer attached in one region, with fluid and tissue debris filling the area between the detached cartilage and underlying bone. Remember our jump painting analogy?  The detached lesions are like paint chips, leaving the wood of the jump exposed, the cyst-like lesions are like bubbles in the paint, detached from the wood, but with the paint surface still intact. 

The prognosis for full athletic function for OCD of the lateral trochlear ridge in the stifle and most locations in the hock is excellent in the majority of cases, particularly when lameness is not severe, and does not become apparent until the horse enters training.  OCD of the fetlock is often treated successfully, but caries a more conservative prognosis in general than lesions of the hock or stifle.  OCD of the shoulder and cervical spine in general carry a guarded prognosis. There are certain anatomic locations where OCD lesions may be detected radiographically in a sound horse during a pre-purchase examination, for example, and be considered clinically insignificant, depending on their severity, and the horse's level of performance.

While surgical debridement (scraping the lesion just as you would scrape the paint on your jumps before correctly applying fresh paint) remains the gold standard for treatment of OCD, there are many emerging treatments under investigation which may alter our approach to this complex disease.  Intra-articular stem cell therapy is one of the most promising of these.  And still, many foals and weanlings with early diagnosis of less severe forms of OCD respond well to simple rest and careful rehabilatation with intra-articular chondoprotective therapy, allowing mother nature to do her own magic in healing lesions.

I've barely scratched the surface of the subject of OCD in these past few posts, but hopefully you will take away the message that in most horses this diagnosis does not mean the end of an athletic career.

I'm off to dinner after a long, cold day of work in windy, 45 degree rain spitting Reno today.


Wednesday, March 10, 2010

3/9/2010 - Osteochondrosis - What is it?

Vet Tip of the Day: Osteochondrosis - Understanding the disease Process
Key Words: Bone, Cartilage, Mineralization, endochondral ossication

Yesterday I discussed the lameness workup on Classy, a 5 years old thoroughbred mare with OCD of the stifle.  So what is OCD anyway?
Today Iwill describe the disease process, and some of the factors we believe predispose juvenile horses to this problem.  Tomorrow I will go over some of the more common location for OCD lesions.

OCD stands for Osteochondrosis dissecans.  Just to give you a hint at how complex this disease is, there is still debate over whether this even is an accurate name for the problem.  To understand this disease at all, you must first understand how bones grow.  A joint is a moving part, consisting of bones that slide along each other, separated and lubricated by joint fluid.  The surface of the bone is covered by a layer of cartilage, which is softer and more compliant than bone, and therefore stands up better than more rigid bone to the forces exerted on joints during athletic activity. 

Think about it - how do your foal's bones get longer and thicker as the foal grows?  What happens is a process called endochondral ossification.  The bones grow from the surface cartilage toward the underlying bone.  The cartilage cells, called chondrocytes, divide and increase in number.  As they mature, they become mineralized and eventually transform into bone.  This is a rapidly ongoing process in the growing foal.  If the transition from young chondrocyte to mineralized chondrocyte to bone doesn't occur correctly, there is a defect in bone maturation.  Thus, osteochondrosis is a defect in endochondral ossification. 

Try this image to help you imagine what happens.  You are painting the jumps in your arena.  You are getting tired, so instead of putting on several thin coats of paint, and allowing each to dry in between, you start globbing on thick layers of paint, not letting each layer dry.  When you lay the paint on correctly, each layer adheres to the one beneath and you end up with a shiny surface of smooth paint that doesn't crack or peel.  If you glob the paint incorrectly, you end up with bubbles underneath the surface and cracks and flakes on the surface soon after the paint dries.  Exactly the same thing happens in foals with OCD.  The cartilage to bone development is abnormal, and the resulting defects include cysts (just like the bubbles under your paint surface) and cartilage flaps that detach from the underlying bone just like your flaky paint, because the attachment to the underlying layers is not healthy. 

Cysts lying just below a thin layer of unhealthy cartilage, flaky, cracked cartilage, and actual flaps of calcified cartilage that separate from the underlying bone are all manifestations of OCD.  In all three cases, the smooth, gliding surface that is critical to pain free, athletic joint function, is lost.  The result is swelling and pain during athletic activity.  Many factors predispose horses to develop OCD.  The particular combination of events in a given foal that result in OCD are complex and inter-related.  Some of the major forces at play are: genetics, rapid growth and large body size, excess feeding of carbohydrate, abnormal stress and trauma, and mineral imbalance, specifically copper deficiency.

This is a very basic overview of the disease process called OCD.  Tomorrow we will look at some of the most common sites in the body where OCD occurs, and the clinical significance of some of these sites.

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