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“Strangles” is a disease caused by the bacterium Streptococcus equi. Characteristics of the disease include an abrupt onset of fever (>103 F) seen 3-14 days after exposure, swollen lymph nodes (lymphadenopathy), and lower respiratory tract signs (nasal discharge starting as clear then progressing to mucopurulent/pus), swelling and abscessation of submandibular and retropharyngeal lymph nodes. Horses will usually develop swollen lymph nodes 1 week after infection and the first sign is hot, swollen, painful lymph nodes. Other clinical signs include difficulty swallowing (dysphagia), pharyngitis (inflammation of the pharynx), difficulty breathing, possible cough, depression, lethargy, and going off-feed. Complications of excessive lymphadenopathy and difficulty breathing may require a tracheostomy.
Horses become infected through exposure in the nose and/or mouth. This can occur through direct and indirect contact from horse-horse contact, fomites (ie, blankets, water and feed buckets, brushes, bridals, halters, etc.), and person to horse. The bacteria, once in the oral and nasal cavity can attach to the tonsils and reach deeper tissues to set up infection within a few hours. Because of the ease of spread, hygiene and biosecurity are crucial components of controlling an outbreak of Strangles on a farm.
Diagnosis of Strangles includes cultures of nasal swabs, nasal washes, or aspirates of pus from abscesses. PCR (polymerase chain reaction) can be used, but it does not differentiate between live and dead bacteria, therefore it is an appropriate adjunctive diagnostic, but culture is the gold standard. Blood can also be submitted to measure the amount of antibody in the horse’s blood to a specific protein from the bacteria called Streptococcus equi M protein. The blood test does not differentiate between a vaccination response or a response to infection, therefore it is an appropriate test to determine antibody levels when checking for necessity for a booster, or in cases of suspect Pupura hemorrhagica (see description below).
Controlling outbreaks require strict hygiene and biosecurity. Quarantine should be established where no horses come on or off the property. Designated areas should be created on the farm as “dirty” and “clean” areas where horses showing signs and/or having a positive culture from a nasal swab or wash should be separated from those not showing signs and/or those with a negative culture. Horse’s rectal temperatures should be taken at least once daily and if they are above 101.0 F, they should be moved to the “dirty” area. Bleach is an effective disinfectant therefore footbaths should be placed at areas entering/exiting filled with a dilute bleach/water mixture. Designated clothing should be worn for only the sick and only the healthy horses.
Treatment with antibiotics is dependent on the clinical signs. In horses that have a fever and signs of depression with no swollen lymph nodes, treatment with Penicillin for 3-5 days may be beneficial. It is generally contraindicated in horses with lymphadenopathy and fever; however, in the case of a fever, anorexia, difficulty breathing, depression, and detectable swollen lymph nodes, antibiotics are warranted to decrease abscess size and prevent complete airway obstruction. In those horses with swollen lymph nodes, signs of depression, and fever, but not showing respiratory distress or severe signs of illness, treatment includes rest, placement in a dry warm stall with soft, moist feed, free choice water, and close monitoring for respiratory distress. Hot packing of abscesses may help to quicken maturity and subsequent rupture of the abscesses. Abscesses that have matured and have a thin membrane along the bottom can be lanced and flushed daily with dilute iodine solutions. Non-steroidal anti-inflammatories (Banamine and Bute) can help with pain relief and help reduce fevers.
To monitor recovery, weekly nasal swabs or pharyngeal washes should be performed and submitted for culture. In horses who have tested positive, endoscopy of the upper respiratory tract and guttural pouches should be performed to check for the presence of chondroids (inspissated pus).
Secondary complications from a Strangles infection can be Bastard Strangles (spread of infection through the blood and lymphatics to distant organs causing secondary complications such as abscessation, bronchopneumonia, septic arthritis, brain abscesses, and ulcerative keratitis), purpura hemorrhagica (immune-mediated syndrome where immune complexes are deposited in blood vessel walls causing vasculitis, swelling of the limbs and low platelet counts), myositis (infection/inflammation of muscles), muscle infarctions, and lack of milk production in pregnant mares.
Vaccination for Strangles should be discussed thoroughly with your veterinarian as to what is appropriate for the barn. It depends on your horses’s job (travel and increased exposure versus stabled at one farm with no travel, etc.). Vaccinations should not be used in an outbreak unless the horse has had no known contact with an infected horse. The vaccine is a modified live vaccine given initially at 2 doses (2-3 weeks apart) with an annual booster.
Be sure when moving your horse to a new farm to check with the farm manager with regards to their policy on vaccinations and/or any history of Strangles outbreaks at the farm. Please contact your veterinarian or the veterinarians at New England Equine Medical & Surgical Center with any questions regarding Strangles.
Kate Britton, DVM
Jacqueline Bartol, DVM, DACVIM
Neck and Back Anatomy and Pain in Performance Horses
Neck and back pain is widely acknowledged to have negative effects on equine performance. However, neck and back issues are often undiagnosed and go untreated. There are many causes for pain associated with the spinal column and most can be treated once they have been properly identified.
Several different anatomical structures must be considered when trying to diagnose neck and back pain. The vertebrae, the bones that make up the spinal column and protect the spinal cord, are divided into five groups.
The seven cervical vertebrae are located from the back of the skull to just in front of the first rib. The eighteen thoracic vertebrae, which also
articulate with the ribs, extend from about the level of the point of the
shoulder and through about 2/3 of the back. The six lumbar vertebrae make up the last 1/3 of the back. The dorsal spinous processes of the thoracic and lumbar vertebrae extend from the main body of the vertebrae (which houses the spinal cord) up to just under the skin. These are the structures that make the shape of the withers. The five sacral vertebrae are located behind the lumbar vertebrae and are fused together to make the sacrum. The sacrum is attached to the pelvis at the sacroiliac joints. The caudal vertebrae vary in number and make up the spinal column in the tail. Intervertebral discs are located between the vertebrae. Many ligaments extend between individual vertebrae and keep the spinal column in alignment. The nuchal ligament (which
extends from the back of the skull to the withers) and the supraspinous ligament (which extends from the withers to the sacrum) are located on top of the vertebral column and act as a “spring” when the horse rounds its neck and back. Finally, the epaxial muscles run along either side of the vertebral column and enable a horse to bend from side to side.
Although many problems can occur with such complex anatomy, there are a few issues that are most commonly seen in the neck and back of the performance horse. In the neck, the joints between the cervical vertebrae (called cervical facet joints) can develop osteoarthritis. This is usually a degenerative process that occurs over time and is more common as horses get older. Narrowing of the facet joint spaces can be seen on radiographs. Proliferation of bone at the joint spaces can also be seen on ultrasound.
Signs of cervical facet joint osteoarthritis may include decreased range of motion in the neck, especially from side to side, reluctance to bend
laterally under saddle and resistance to the bit when bending. The facet joints can be medicated under ultrasound guidance with steroids, which decrease inflammation in the area and will often make the horse more comfortable for 6 months to a year. In conjunction with joint injections, horses will often benefit from neck stretching exercises (“carrot stretches”) and non-steroidal anti-inflammatory drugs (such as phenylbutazone).
Another common condition is overlapping or overcrowding of the thoracic and lumbar dorsal spinous processes, also known as “kissing spines”. This occurs when the spaces between the dorsal spinous processes decrease, causing inflammation and bony changes. This can occur secondary to trauma but is probably more commonly associated with exercise and spinal conformation. It is particularly common in hunters and jumpers and horses may refuse to jump. Kissing spines can be particularly painful because they often occur where the saddle sits on the back. Horses may resent the saddle and palpation of the back and may move quite stiffly. Diagnosis of kissing spines may
include deep palpation of the back, radiographs, ultrasound or nuclear scintigraphy (bone scan). Once accurately identified, the narrowed spaces between the dorsal spinal processes can be medicated with steroids. The muscles surrounding the affected bones may also be quite tight and will add to the pain associated with kissing spines. Steroid injections into the surrounding muscles and mesotherapy (intradermal injections to decrease pain conduction) will help break the pain cycle and allow horses to continue exercising and building back muscles.
It is important to remember that back pain can be caused by compensation for lameness in either the front or hind limbs. When diagnosing a horse with back pain, the entire clinical picture must be taken into account. However, with more awareness for neck and back diseases, horse with decreased performance due to neck and back pain are being diagnosed and treated more appropriately.
A. Rachel Roemer, DVM
Omar Maher, DV, DACVS
So you're taking the plunge and looking to buy a horse? Regardless of if this your first horse or fifth, there are a few important things to keep in mind.
When looking for a horse, keeping an open mind will often help you find your best fit. Depending on what you are looking for, your potential market may be limited, for instance a completely sound schoolmaster may not exist. If you are just getting into horses or a beginner rider, you should look for horses that are well-trained as opposed to green or just off-the-track. Even if you are looking to sell your horse at a later date, temperament is important in developing a relationship with your horse.
If your potential horse is horrible to be around or has vices like cribbing that
are difficult to deal with, it may not be for you. A trial period or short term
lease will let you get to know the horse in your environment and learn if there are any problems prior to getting a pre-purchase.
When selecting a veterinarian for a pre-purchase exam, go with what you know! If you already have a relationship with a vet, take advantage of it. The better the vet knows you, the better they will be able to evaluate whether the horse fits your needs. If you don't already have a veterinarian, research vets in your area that are well known in your discipline, or a vet that your trainer or friends recommend.
A vet in your discipline will have a good idea of the level of performance your potential horse will have to cope with. You should feel comfortable communicating exactly what you are looking for in a horse to your vet, and your vet should be able to give you an experienced opinion as to their findings. The American Association of Equine Practitioners (www.aaep.org) has a database of member veterinarians if you wish to find one in your area.
The pre-purchase exam has a number of components, and depending on the value of the horse and level of performance you are expecting, there are a wide range of options available. If you are looking for a backyard pony, for instance, a general health check may be sufficient, but if you are looking for a Grand Prix show jumper, extensive radiographs should be taken to ensure the horse's soundness.
First of all, a detailed medical history of the horse should be available from the seller or the seller's veterinarian. The history should include prior medial issues, surgeries, lamenesses, any medications the horse has been treated with, vaccine/deworming records, and training/competition history. The seller will hopefully be honest, as the veterinarian may not be able to find everything during the exam. The work and competition history may be helpful to explain any issues found later on in the exam as well. The health
evaluation should include listening to the heart, lungs, and abdomen for any heart murmurs or arrhythmias, heaves, or sand in the GI tract. The vet will examine the eyes and nose for any discharge, the ears, and the musculature of the head for any neurologic problems. They should also do a basic dental exam to make sure the horse does not have significant dental problems that have not been previously addressed, as well as to check the horse's age. The confirmation of the horse will be assessed, which could tell a lot about potential problems or how suited the horse may be to its job. The hooves should be checked for routine trimming or shoeing, and depending on the horse, to see if it has been nerved. The vet will palpate all over the horses body, checking for swelling, pain or scars.
In most instances, a lameness evaluation will follow. Hoof testers will check for any soreness in the feet, such as navicular syndrome, pedal osteitis or laminitis. The horse will walk and trot on a straight line and in circles to assess movement on both hard and soft ground, as different injuries may be evident based on the footing. The horse may also be ridden under saddle to assess movement, back problems, or respiratory issues. Flexion tests will isolate pain to certain joints and will be graded on a scale. Based on the flexion tests and the horse's value, radiographs will be taken to investigate any issues or ensure general soundness. Digital radiographs have become quite common recently and are faster with a great amount of detail,
so if you are planning on taking a lot of radiographs, a vet with digital capabilities may be a better fit. Special radiographs can also be taken of the neck, back, skull, and other areas.
An ultrasound exam could be used to assess integrity of soft tissue structures, but are usually reserved to further investigate an abnormal finding. A horse that will be used for breeding, however, should have a rectal ultrasound to check the reproductive tract.
Depending on the horse's job, endoscopy or gastroscopy is a possible test. The endoscope is a small tube with a camera on the end that is passed through the horse's nose. It can be used to assess the upper airway in the performance horse, or the stomach for ulceration. The horse must be fasted prior to gastroscopy, and may require sedation. Bloodwork may be run on the horse for a variety of tests. A Coggins should be drawn to test for Equine Infectious Anemia, and is required for travel. Depending on the state, a Coggins needs to be drawn every 6 months to a year. A complete blood count and chemistry panel can check for general wellness, possible infection, and organ function. Drug testing is available as well. Other
more extensive testing includes nuclear scintigraphy ("bone scan"), MRI, neurologic tests, and an echocardiogram or ECG. These tests would not be recommended other than to follow up on an abnormality found previously. For sport horses especially, blood should be pulled and either analyzed or stored for later analysis for possible drug administration.
In closing, you should make sure your vet knows what you want in a horse, and your vet should make recommendations based on their findings, as well as the horse's temperament and intended use. They will give you a written report and will include radiographic interpretation if they were taken. If you have any questions about pre-purchase exams, feel free to contact the veterinarians at New England Equine Medical and Surgical Center.
Cara McNamee, DVM
Omar Maher, DV, DACVS
Foals can be affected by omphalitis (infection/inflammation of the umbilical structures) which can be due to inflammation of the umbilical arteries, umbilical vein, urachus, or tissues surrounding the umbilicus. Omphalophlebitis is infection of the umbilical vessels. The urachus is a structure that in utero transports fetal urine from the fetal bladder to the placenta. It normally will close at birth, but can become infected and/or inflamed in neonatal foals. After birth, blood flow no longer occurs in the umbilical arteries and vein, and they become ligaments in the abdomen. These structures can each serve as areas of infection. Umbilical remnant infections have been referred to in the past as “navel ill”.
There are some predisposing factors that can put a foal at greater risk of developing an infected umbilical remnant due to infection spreading to the umbilicus or associated vessels such as a foal with failure of passive transfer (lack of intake of colostrum). Healthy foals can also develop local infections of their umbilical remnants, and this is one of the reasons why it is very important to clean the umbilicus with diluted chlorhexidine or dilute betadine solution in neonatal foals.
Clinical signs important to watch for in the cases of omphalitis/phlebitis depend on whether the infection is due to a systemic infection or due to a local infection.
• Local: umbilical swelling, purulent (pus-like) discharge, swelling along the lower abdomen, pain, and/or heat around the umbilicus.
• Systemic (septic): fever (greater than 102.5 F), depression, recumbency, inappetance/loss of suckle, signs associated with systemic infection (increased respiration, difficulty breathing, diarrhea, colic, swollen joints, lameness), along with general clinical signs associated with a local umbilical infection.
Treatment options for umbilical remnant infections consist of medical and/or surgical therapy. Your veterinarian can perform a physical exam, bloodwork, and possibly an ultrasound examination to determine the extent of infection.
•Medical: This is preferable in small, localized infections in foals that are not good anesthetic candidates. Treatment includes broad spectrum antibiotics (2-3 week duration at times), with frequent re-evaluation through assessing vital signs (temperature, pulse, respiration, general demeanor), bloodwork values (especially fibrinogen) and ultrasonographic exams of the umbilical remnants. If there is no improvement within 7-10 days, a change in antibiotics is recommended; however, surgical intervention to remove the entire remnant may be necessary if the foal does not respond to medical therapy.
•Surgical: This is the most definitive and is the standard treatment.
A foal with a systemic illness (septicemia) should be stabilized prior to surgery, but complete removal of the infected remnant is essential so as to prevent future seeding of the remnant and other parts of the body (joints, lungs, GI) with infection. The entire remnant is removed including the arteries up to the level of the bladder and the vein extending to the level of the liver. Bacterial culture should be performed on the stump to direct appropriate antibiotic treatment.
When caring for a foal, it is important to contact your veterinarian at the first signs of a depressed attitude, lethargy, changes in eating, fever, colic, cough, lameness, swelling, discharge, or heat around the umbilicus, or any signs of discomfort in your foal. We recommend a routine foal check at 24 hours of age. Your veterinarian can assess the foal’s overall health and condition and determine if the foal has any predisposing factors for infection. An IgG level should be checked at this time. Umbilical infections are one of the primary sites of infection in a foal that does not have an IgG level of greater than 800.
If you have any questions regarding foal care and health or specific questions about umbilical infections, please contact your veterinarian or any of the veterinarians at New England Equine Medical & Surgical Center.
Kate Britton, DVM
Jacqueline Bartol, DVM, DACVIM
Lyme Disease and Anaplasmosis
If you have been walking in the woods or tall grass, you have probably noticed that the ticks are out in full force. With them comes the emergence of tick-borne diseases. In horses in the Northeast, we mainly see Anaplasmosis ( previously Ehrlichiosis) and Lyme Disease as causing problems.
Formerly known as Ehrlichia equi, Anaplasma phagocytophilum is a rickettsial bacteria in the same family as the organisms causing Typhus and Rocky Mountain Spotted Fever in humans. A. phagocytophilum is not contagious to humans, nor can horses transmit it to each other. The disease is transmitted to the horse by Ixodes sp. ticks, which in the Northeast is Ixodes scapularis, more commonly known as the Deer Tick or Blacklegged Tick. Immature ticks pick up the bacterium from rodents who serve as reservoirs, maintain it as they mature, and then transmit it to the horse they feed off of as adults. It is unknown how long the tick has to be attached before transmission occurs. It takes approximately 2-3 weeks after disease transmission for the horse to develop clinical signs of Anaplasmosis, meaning that by the time signs are noticed the tick is long gone. The most common signs seen by owners are depression/lethargy and a high fever, as high as 104-105° Fahrenheit. Other signs can include limb edema (swelling), petechial hemorrhages (small red/purple spots) on the mucous membranes, icterus (yellow mucous membranes), and poor appetite.
A. phagocytophilum organisms infect neutrophils and eosinophils in the blood, and this is one method of diagnosis. A direct evaluation of a blood smear from the horse can reveal the organisms within these cells, making the diagnosis very straightforward. Another method of diagnosis, usually used on farm and then confirmed with a blood smear, is the use of the canine 4Dx snap test. In dogs this simple test using only a few drops of blood tests for heartworm (Dirofilaria immitis), Lyme (Borrelia burgdorferi), Anaplasmosis (Anaplasma phagocytophilum and platys), and Ehrlichiosis (Ehrlichia canis). Conveniently, this test can be used in our horses for both Lyme and Anaplasma diagnosis. While it is not perfect, it is a good, quick, stall-side diagnostic tool that can be used to direct further testing or treatment. If laboratory bloodwork is submitted, thrombocytopenia (low platelet count) is very commonly seen, which can be low enough to cause spontaneous bleeding and hemorrhages of the mucous membranes. Low red blood cell and white blood cell levels can also be seen, which can be severe enough to cause weakness, and increase susceptibility to other infections, respectively. If questions exist about a diagnosis, an immunofluorescent antibody test (IFA) can be submitted to quantify an antibody response against A. phagocytophilum.
In the Northeast, a horse with an extremely high fever but no clinical signs of viral respiratory disease (another possible cause of such high fevers) is highly suspected of having Anaplasmosis. If confirmed by snap test or blood smear, the treatment is fortunately straightforward. Oxytetracycline intravenously for 3-5 days is the preferred treatment, although oral doxycycline may also be used with somewhat more variable results and timeline, as its absorption from the GI tract is not as predictable. The fevers usually subside very quickly and the horse feels much better within 2-3 days, with no lasting effects. Prolonged treatment is not necessary, and horses gain some protective immunity from the infection, although how long this protection lasts is not known. Anytime a horse has a very high fever, the concern for potential side effects such as laminitis and abortion cannot be ignored, however these are not generally seen with Anaplasmosis. Prevention is difficult; some horses have a natural immunity likely stemming from exposure and disease which was so mild it went unrecognized, but the key lies in tick control. Permethrin-containing tick repellant products are available but ticks may still be able to attach and transmit disease. Environmental management such as keeping grass trimmed short and horses out of the wooded and brushy areas preferred by ticks is helpful. Grooming your horse thoroughly after rides in tall grass or wooded areas may help dislodge ticks which haven’t attached, but it is difficult to comb through every hair of your horse to find all the areas ticks might be hiding. No vaccine is currently available.
Lyme disease is a commonly diagnosed problem in the Northeast, though many lameness or neurologic issues may be unfairly ascribed to it. A very large proportion of horses have been exposed to Borrelia burgdorferi and have antibodies to it, which are picked up in the canine snap test. A positive snap test may be associated with an active infection, but horses with a positive snap test plus clinical signs consistent with Lyme are commonly treated and in many cases, improvement is seen. The disease, like Anaplasmosis, is transmitted by Ixodes scapularis which pick up this spirochete bacterium from rodents as nymphs then transmit it to the horse as adults. Again, it is not known how long the tick must be attached for transmission (research has shown it may be 24-48 hours), and it may be several weeks before signs are noted, and infected horses do not transmit disease to humans or other horses. The signs of Lyme disease are varied and vague in horses, including shifting limb lameness (“Today the right front, yesterday the left hind, what’s going on?!?!”), mild fevers, stiffness, sensitivity to touch, muscle soreness, attitude changes, swelling in multiple joints, decreased appetite, and a host of things which fall into the ‘he’s just not quite right’ category.
If a snap test is positive, confirmation can be obtained by Western Blot and ELISA testing (usually performed concurrently). Likewise, if the snap test is negative but the disease is still highly suspected, these tests may be submitted to make sure the snap result was not a ‘false negative’. In horses with neurologic disease in which Lyme is suspected, cerebrospinal fluid may be submitted as well, to determine whether organisms have affected the central nervous system. Lyme frequently causes inflammation in the synovial lining of multiple joints, which accounts for many of the signs seen. A full lameness and neurologic evaluation may need to be performed along with testing to help rule in or rule out the disease. Laboratory bloodwork (CBC, Chemistry panel) does not tend to show anything specific.
If a horse is suspected or confirmed to have Lyme disease, like with Anaplasmosis, tetracyclines are the drugs of choice. Most horses are put on oral doxycycline as this is easy to do at home, but the course of treatment can be many weeks to months. Another way to treat is to give intravenous oxytetracycline in a hospital setting twice daily for 3 weeks. For these horses, kidney values must be monitored as the prolonged treatment can cause kidney damage in some cases. If elevations are seen, the treatment can be reduced to once a day; if elevations continue or are severe, the treatment must be stopped. The kidney damage, as long as it is caught quickly, is not permanent, but prolonged treatment with no knowledge of kidney function could result in permanent damage. Horses undergoing intravenous treatment may also continue treatment with oral doxycycline once they go home. Once treated, horses can be tested in 3-6 months as the antibodies take a long time to disappear from the blood stream, and a false positive result may be obtained. And again, a positive test in a horse who has been treated does not necessarily indicate another active infection, it could be exposure with an immune response that protects the horse from disease. There is no approved equine Lyme vaccine. However, in horses that test negative on ELISA and western blot, a canine Lyme vaccine may be used to attempt to prevent infection. This should be discussed with your veterinarian and the decision made based on an individual horse by horse basis.
If you have any questions about Anaplasmosis or Lyme disease please contact your veterinarian or the veterinarians at New England Equine Medical and Surgical Center.
Susan Barnett, DVM Jacqueline Bartol, DVM, DACVIM
Any horse that is not vaccinated properly is susceptible to Tetanus. With the poor prognosis for recovery and low cost for this vaccine, there is no reason that any equid should not be protected for this disease.
The classic picture of a horse with tetanus is a rigid stance with an inability to open the jaw muscles. Other clinical signs that accompany tetanus include elevated tail head, protrusion of the third eyelid over the eye and a spastic gait. These signs often become more pronounced following a sharp, loud noise, such as clapping of the hands.
The signs of tetanus are caused by a toxin released by the bacteria Clostridium tetani. The bacteria usually gains entry to the horse’s body through a hoof or other soft tissue wound and the toxin affects nerve function in the spinal cord and brain. Nerves in the body are influenced by signals (neurotransmitters) that stimulate and inhibit the nerve. The toxin secreted by Clostridium tetani blocks the signals that inhibit the nerves. This results in spastic muscle response, that can be exacerbated with sudden excitement.
A diagnosis of tetanus is based on the observed clinical signs in an unvaccinated horse. There are no blood tests, although culture of a concurrent wound for C. tetani can be attempted. Often, clinical signs are observed 7-10 days after a wound has occurred.
Although the prognosis for survival is poor, treatment can be attempted. Treatment focuses on five things:
1). Debriding and flushing the wound to reduce remaining number of Clostridium bacteria – The wound is left open for drainage and in some cases the antibiotic penicillin is flushed into the wound.
2). Neutralizing any unbound toxin that has not yet bound to the nerves – Toxin can be present circulating in the blood, as well as in the cerebrospinal fluid bathing the spinal cord.. Tetanus antitoxin is given intramuscularly to bind any circulating toxin in the blood. In some cases, it is also injected into the cerebrospinal fluid, as intramuscular administered antitoxin does not cross into the nervous system.
3). Providing muscle relaxation/tranquilization - Acepromazine, a tranquilizer, is given to relax the muscle spasticity and the patient’s excitement.
4). Supportive care – A quiet dark stall is best to minimize stimulation. The toxin also affects the muscles that are responsible for drinking and eating. Therefore, these horses are often placed on intravenous fluids to keep them hydrated. An indwelling stomach tube can also be placed to supply calories if the patient cannot swallow food.
5). Stimulating an immune response – An affected horse may not start producing antibodies against the toxin, since even a low level of toxin can cause disease. Therefore, the horse should also be vaccinated at some point with a tetanus toxoid. This is a killed version of the toxin that elicits an immune response.
In conclusion, every horse should be boostered yearly with a tetanus toxoid vaccine. If the horse has sustained a wound and has not received the vaccine within the past 6 months, it should also receive a booster at that time. Sometimes, a tetanus antitoxin is given to a horse with a current wound and unknown vaccination history. This only provides coverage for a few weeks. A potential side effect of the tetanus antitoxin in horses is serum hepatitis or liver failure. This is uncommon, but can occur and should be mentioned.
If you have any questions regarding tetanus or vaccination of your horse, then please don’t hesitate to call.
Andris J. Kaneps, DVM, PhD, DACVS
Karyn Labbe, DVM