Spider Bites

I think of winter as a time when bugs and snakes and things that cause nasty bite wounds are asleep.  While this is mostly true for our friend the rattlesnake, I learned last week that it is not so for spiders, when I was called out to see Venus, a 12 yo thoroughbred mare.
 
Venus was fine the night before when her owners closed up the barn, but they came out Sunday morning to find her standing in her stall with her head down, breathing heavily, unwilling to move, with a severely swollen hind leg.  On my arrival, initial examination revealed an elevated heart rate (80 beats per minute/normal 40), respiratory rate (24 breaths per minute, normal 12), and temperature (104.5 F, normal on a digital thermometer 99-100).  Venus was exquisitely painful - her breathing was shallow and panting, when forced to move she hopped on her right hind leg, and the leg was 3x normal size, from the pastern to the stifle.  The swelling in her leg was warm and very painful to touch.  After careful examination of the leg, I discovered a tiny red spot on the lateral aspect  of her metatarsus (outside of the cannon bone).  The skin immediately surrounding this spot was weeping a clear yellow fluid.

The rule outs for acute, severe swelling and lameness in a limb are abscess, infection, and fracture.  The most common is a foot abscess.  However, it would be extremely unusual for a hoof abscess to cause swelling extending this far up the limb and such a high fever to develop in just 12 hours.  Nevertheless, I pulled out my hoof testers and performed a careful examination of the hoof before crossing this one off the list.  Next to eliminate was fracture of the tibia or femur.  These bones in the upper limb, when broken, may be associated with severe swelling of the surrounding muscle masses.  However, the presence of a high fever was not consistent with fracture, and once Venus was brought out of her stall and moved around a bit, she did bear full weight on the leg when standing.  This did not completely eliminate the possibility of fracture, but made it less likely.  Upon discovery of the red spot with serum oozing around it, the high fever, severe pain, sudden onset of swelling and lameness were most compatible with a diagnosis of cellulitis of unknown origin.

Cellulitis literally means inflammed cells.  It describes a condition where something - trauma, bacteria, virus, toxin, cancer - sets off a cellular reaction that causes the body to release fluid, white blood cells, and a wide variety of small chemical molecules into a region of the body in response to the insult.  This is the body going to war - these factors are the body's soldiers and weapons that it uses to kill invading organisms.  Unfortunately, as in any war, there is collateral damage, and the body not only attacks the enemy, it also attacks itself.  The result is swelling, heat, pain, and redness, the four classic signs of inflammation (rubor, calor, tumor & dolor in latin - these signs have been recognized since ancient times).

The yellow fluid leaking through Venus' skin was serum - as the cells in her skin and underlying interstitial tissues fell apart, the blood and lymph vessels in the area also lost their integrity, allowing the fluid that should be retained within the body's plumbing system to leak out.  The damage to Venus' leg was so severe that this liquid was exuding through her skin - the body's final and most important barrier to the big bad outside world.

Whatever the initiating cause of cellulitis, the destruction of the body's intricate array of barriers to the external environment allows immediate invasion of infectious organisms that always are lurking about- primarily bacteria.  In a barn setting, these bacteria are everywhere because they love to live in warm organic matter - manure, bedding, wet spots under water buckets - I'm sure you can  imagine many more if you look around your barn and paddocks.  Although to us hairless humans winter feels very cold, in our climate prolonged deep freeze is actually rare - and if you dig to the bottom of the manure that's been accumulating since November in the corner of a pen, you'll likely find some warm, wet spots that are the bacterial equivalent of our mid-winter Baha vacation haven.

So, let's take a step back and decide what to do for Venus.  Although at this point we have not determined the definitive cause of her clinical signs, we have put together the fever, painful swelling, and serum leakage as indicators of cellulitis as the most likely primary problem.  We have reasoned that cellulitis is associated with inflammation and infection, therefore our initial treatment should be directed against 1) pain 2) inflammation 3) infection.  On a scale of 1-10, I gave Venus' condition a clinical score of 8 - very severe.  When choosing medications, we must chose oral, intramuscular or intravenous routes of administration, and we must choose drugs according to their strength and spectrum of activity.  Venus needed the big guns - so she was given intravenous flunixin meglumine (Banamine - anti-inflammatory/analgesic), Gentocin (antibiotic) and Potassium Pencillin (antibiotic) as well as an intramuscular tetanus toxoid.

The next concern was hydration and nutrition.  I decided to monitor Venus' reponse to therapy for 24-48 hours.  She did improve, but it was not logistically possible to continue frequent intravenous antibiotic adminstration and Venus did not eat or drink well over the next 48 hours, so the decision was made to hospitalize her where she responded rapidly to intensive medical therapy.  She returned home a healthy, sound horse, although she continued to loose hair and some skin on the affected leg for 10 days after the initial insult.

What happened to Venus?  The owners reported finding a Black Widow spider in the tack room next to Venus' stall a few days before her adventure began.  They have had problems with these spiders in the past.  Although we cannot know for certain, I believe that Venus was bitten along the side of her cannon bone (the red spot leaking serum) by a Black Widow.

We have two spiders in our area that cause toxic bite reactions.  The picture at the top of the blog is a Brown Recluse.  The actual Brown Recluse species is rare in Northern Nevada, but we do have a closely related species.  The bite of the Brown Recluse and its relatives causes a severe, localized, necrotizing reaction, but not a generalized response. The site of brown recluse bites initially is warm and painful, and over the subsequent 3-7 days may develop into a deep, debilitating open wound with massive loss of tissue and secondary infection.

The Black Widow bite contains a neurotoxin.  It travels through the body and tends to cause more systemic signs which can range from muscle pain to neurologic signs, depending on the site of the bite and the size of the victim.  While dogs are quite resistant to the affects of Black Widow toxin, horses are very sensitive. To learn more about these two spiders, visit Slideshow: Black Widow Spider vs. Brown Recluse Spider on eMedicineHealth.com 


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

The Will to LIve

The Will to Live

     

     Three years ago, Angel was born dysmature and septic.  Angel could not stand, could not suckle, and had a bacterial infection (neonatal septicemia) affecting her entire body.  Hospitalization in a neonatal intensive care unit was not an option due to financial constraints.  Under the best of circumstances the likliehood of survival in this situation is 20%.  In an at home care setting, it is drastically reduced.  Somebody forgot to tell Angel.

We set up a MASH unit in the outdoor paddock where Angel and her dam lived.  Angel’s human family basically stopped eating or sleeping for the next 10 days.  I provided Angel with an intravenous catheter and a nasogastric feeding tube, and administered initial aggressive treatment to address the immediate issues of failure of passive transfer, sepsis, inadequate caloric intake, toxemia, and possible cerebral anoxia, and gave the owners a crash course on IV medication and fluid administration, feeding tube maintenance, and neonatal foal nursing care.  Remember, Angel couldn’t stand  – she could barely lift her head.

     Angel required around the clock care and she got it.  As day 1 became day 2, then 3…6…10 I watched amazed as Angel’s owners gave life to this gritty little filly.  As the caregivers began to look increasingly weak and exhausted, Angel did just the opposite – by 2 weeks of age she was a bouncing, active, clinically normal foal.  We all danced for joy (well, her owners watched with bleary eyes while I danced – they were just too wooped to jump around) and Angel set off to live a normal life.

     Turn the clock ahead to late summer, 2010.  Angel is now 3, and has been sent off to spend some time with a cowboy trainer.  She went on a slow cattle drive and had some great experience just learning to be out and about with other horses.  Unfortunately, there was an outbreak of Strangles on the ranch while she was there.  Strangles is a strep bacteria: Streptococcus equi sp. equi.  It is highly contagious.  A typical case of Strangle goes like this: the horse is exposed to the bacteria.  Three to five days later the horse is depressed and has a fever.  This may go unnoticed.  By day seven the horse has a thick yellow nasal discharge.  Over the next week to ten days, the horse develops swelling just behind the cheek bones (retropharyngeal) or between the jaw bones (submandibular) caused by lymph node abscessation.  These abscesses break open and drain, the horse recovers and that’s that.  An uncomplicated case of Strangles is not treated with antibiotics, and has no long lasting consequences for the horse.

     Complications occur in about 10% of horses with Strangles.  These include abscesses that compress the airway and interfere with breathing or swallowing, pneumonia, formation of internal abscesses within the abdominal cavity, and an uncommon immune mediated disease called purpura hemorrhagica.  All complicated cases of Strangles require intensive medical treatment and are potentially fatal.

     Angel didn’t handle her Strangles well.  By the time her owner was notified and came to see Angel she had been sick for 3 weeks.  She had multiple abscesses on the left side of her face and neck, she had pneumonia, she was suffering from severe malnutrition, and to top things off, she had multiple foxtail abscesses under her tongue and in her throat.  This picture was taken the day Angel came home.  She was weak, staggered as she unloaded from the trailer, had long strings of saliva falling from her mouth, and stood with her head extended, her eyes half closed.  Her heart rate, respiratory rate and temperature were elevated and she had difficulty breathing.  Her hip bones and back bone were prominent – I estimated her weight loss over the 3 weeks at over 100 pounds.

      Once again, the MASH unit was organized.  However, instead of a 65 pound neonate, the owners were now trying to manage a critically ill adult.  I placed an intravenous catheter and we began intensive antibiotic, anti-inflammatory and fluid treatment, but when Angel’s initial blood work came back from the lab, it was obvious that we were not going to able to provide adequate care at home.  She was suffering not only from a critical bacterial infection, but also from severe cachexia.  Our bodies burn many additional calories when we are ill.  Angel’s ability to prehend, chew and swallow had been compromised for 3 weeks, and to compound this problem, she had been competing for food in a group of horses.  In her increasingly weakened condition she had been left with the poorest quality hay to try and consume.  Her blood protein levels were alarmingly low – her body was consuming itself in an effort to fight the infectious process and it was losing the battle. 

     Angel’s owners and I sat down and had a heart to heart.  None of us were willing to give up on Angel, even though it was clear that she once again was facing an immediately life-threatening situation with a guarded prognosis for recovery.  I called UC Davis and arranged for an emergency referral.  Angel’s owners loaded her up and off she went.  Angel , whose normal body weight is 950-1000 pounds, weighed 760 pounds on arrival at the University hospital .  Diagnostic testing including ultrasound and endoscopy confirmed the presence of pneumonia and multiple upper airway abscesses.  Under the excellent care of Dr. Dawson, a senior medicine clinician and her staff, Angel once again defied the odds.  She was in the hospital for close to 3 weeks, and continued her treatment at home for another month.  By Christmas Angel had recovered completely from her second brush with death.  Here she is, head up, bright eyed, and round barrelled.

     It takes a village.  Angel has a tremendous will to live.  She also has a family who loves her and doesn’t hesitate in the face of adversity.  Grandma, grandpa, grand-daughter, the entire medicine staff at UC Davis, the benefactors who support the UC Davis Emergency fund, the Care Credit organization, myself and my assistants, all played roles in Angel’s survival. 

     These days we see and hear a lot of stories of loss, of animals suffering because the money isn’t there, because people give up.  Angel’s owners are not wealthy, but they were willing to look for help when they needed it, and to roll up their sleeves and work themselves to the point of exhaustion to care for their horse.  Their dedication and Angel’s desire to survive are insipirational.

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

Go to Facebook

Hi there.  I haven't been blogging through the busy warm seasons and suddenly it is 2011 and I have NO EXCUSES.

I have found that sometimes it is more convenient to post short educational pieces or links to informative articles directly on our Facebook Page.  Therefore, if you don't see fresh info on this blog, be sure and check out the HighDesertEquine Facebook page, or just click on the Facebook link on our website home page at HighDesertEquine.com.

If I haven't seen you recently, feel free to comment here or on our Facebook page - and as always, let me know what you want to hear about and I will try to address your topic of interest quickly!

Please become a fan or friend of the Facebook page  - it helps it circulate to more people.

Take care,
Dr. C






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

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

The Horse | Shoeing in the Frontal and Horizontal Planes

The Horse | Shoeing in the Frontal and Horizontal Planes

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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.

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.