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Stallion Showcase: Stem cells and the future of horse health

Stem cell therapy has been utilized in horses to help heal tendon, ligament and joint injuries for more than 25 years, and new uses are always being explored. These stem cells are mesenchymal stromal cells (MSCs), which are isolated from fetuses, foals or adult horses, as opposed to embryonic stem cells from embryos. The MSC stem cells can be isolated from almost any tissue, but are most commonly obtained from bone marrow, fat tissue, and from the umbilical cord of newborn foals.  

The two main methods are use of the patient’s own cells (autologous cells) or cells from another horse (allogeneic cells).  

Autologous Cells 

The advantage of using autologous cells is that they are not rejected by the patient’s immune system, and there are fewer regulations for use. The disadvantage of using autologous cells is that it takes 2 to 3 weeks to expand the cells prior to use, to get enough. This involves a two-step process requiring the horse to return for treatment after initial sample collection. This may hamper optimal treatment time since an adequate number of cells are not readily available. 

Allogeneic Cells 

Allogeneic cells have the advantage of being already available, with time to select and potentially enhance cell functions prior to use.  

The disadvantage is that cells from another horse are recognized by the patient’s immune system (and rejected) faster than autologous cells. Also, the regulations are different; allogeneic cell product development is considered drug development  

Drugs vs Devices 

A number of veterinarians, clinics and stem cell companies have treated thousands of horses with stem cells for many years. They started by treating soft tissue injuries and then progressed to treating joints. Some have also treated laminitis with stem cells.  

There was such an expansion of stem cell therapy in veterinary medicine that the FDA became involved, to make sure it was regulated and that this kind of therapy wasn’t being used inappropriately. Use of stem cells was put on hold, and the FDA ruled that stem cells fell into the category of drug therapy. That meant regulations for bringing a new drug to market, apply which requires years and a lot of money. There was very little stem cell use in horses for a number of years. 

Today, most commercial strategies are focused on developing frozen allogeneic cell products. One approach is use of allogeneic stem cells from umbilical cord blood that could be basically off-the-shelf/storable and given to any horse. Two products have been approved in Europe, and trials are underway in North America to get equine products approved here. 

There are no approved stem cell products currently available in North. Other regenerative therapies like platelet rich plasma (PRP) or interleukin receptor antagonist protein (IRAP), fall under the FDA’s category of devices rather than drugs. “There is a big difference between getting a device approved by FDA and getting a drug approved,” says Dr. Thomas Koch, associate professor, Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Canada. “It is very expensive and time-consuming to get a drug approved, which is a big impediment for veterinary medicine. From a pharmaceutical perspective it is a very small market,”  


Koch is founder and CEO of eQcell, a company that is starting two trials using stem cells in equine synovitis and early stages of osteoarthritis–one at University of Guelph’s Ontario Veterinary College Equine Sports Medicine and Reproductive Centre, and the other trial at the University of California-Davis Veterinary Institute for Regenerative Cures (VIRC).  

The Canadian study in equine fetlock and carpal joint osteoarthritis is authorized by Health Canada’s Veterinary Drug Directorate and is the first stem cell trial in Canada for treatment of equine osteoarthritis. The U.S. study in fetlock osteoarthritis is being conducted under VIRC’s Investigational New Animal Drug (INAD) with the FDA. 

Collecting and Growing Stem Cells 

“The cells we are working with are from umbilical cord blood of newborn foals,” Koch says. “My PhD work reported on the presence of these cells in 2007. This had been reported in humans, but we were the first to see if we could find similar cells in equine umbilical cord blood.” 

Koch continued that work after he finished his PhD.  

His company gets the cells from umbilical cord blood. Most people get it from bone marrow or fat tissue. 

“These cells adhere to certain types of plastics. In the lab we use plastic culture dishes. In the first few days a lot of cells are just floating in the media and don’t attach, and then some start attaching to the plastic. When we aspirate the media off and replace it with fresh media, this gets rid of all the floating cells. We end up with a cell population stuck to the plastic.” 

After 8 to 12 days some of the cells on the dish start to form colonies, undergo cell division and expand. “We use enzymes to lift them off the plastic; the enzymes cleave the binding without damaging the cells. We harvest them this way and split them into 3 to 5 flasks of the same size. Those cells reattach and keep growing. We can eventually grow them into billions of cells,” he says. 

The original cells from umbilical cord blood come from breeding farms. “I work with Standardbred and Thoroughbred farms in southern Ontario. During foaling season they have eQcell’s collection kits, and whenever a foal is born, the attendant clamps the umbilical cord. When the foal stands up, the cord simply breaks at its natural breaking point. With the clamp across it (toward the mare side) the blood is not gushing out from the placenta, and is saved.” 

The attendants use a blood transfusion bag to collect it. “These bags come preloaded from the company, with anticoagulant and a needle on the end. The attendants clean the cord and put the needle into the blood vessel within it, and the blood can drain into this collection bag. It’s non-invasive; you are just saving the blood that would otherwise drain out and be lost.” The infusion bag can be stored in a refrigerator overnight, then shipped by FedEx to the lab.  

“What’s nice about this source of cells is that they are as young as we can get them, and consistent. The cells are from newborn foals, and mares that have no signs of disease during the pregnancy,” he says. 

There are advantages to having very young cells. “If you get cells from fat tissue, blood or bone marrow from adult horses, they may be damaged. All cells age, so even if you have a healthy, normal animal, there are stringent requirements for donor testing.” With foal cells, there is some variability between one foal and another, but these cells are more consistent.  

Osteoarthritis Treatment 

Koch says the many treatments being used for OA indicate there’s not one really good answer to the problem of osteoarthritis.  

“There are many products being used for OA, and veterinarians have different preferences in treatment,” Koch says. “This indicates that no one treatment has been shown to be superior. There is interesting data in humans and animals, however, showing that stem cells may be useful in treating some joint conditions.” 

Stem cell therapy holds a lot of promise because it has several advantages over traditional pain medications like phenylbutazone, “bute,” which merely mask pain and has a narrow window of safety and can have damaging side effects, and can’t be legally used in competition. 

Some biologic products, like PRP and IRAP can be injected into joints, and there are fewer regulations regarding their use, as opposed to stem cells. “But it’s hit or miss whether they work, depending on the individual horse,” says Koch. Steroids have also been used for treating OA, but there is controversy about using those in joints because they may damage the cartilage.  

Stem cell therapies are gaining interest because they have several advantages. “There are now two cell products approved in Europe for treating inflammatory joint pain in horses caused by synovitis and early OA,” Koch says. “These are HorStem and Arti-Cell Forte. They both use culture expanded MSCs. HorStem utilizes cells from equine placental umbilical cord tissue, and Arti-Cell Forte isolates MSCs from peripheral blood of adult horses. These two products are both approved for use in horses with joint pain due to early stage synovitis but are slightly different in formulation.  

“HorStem contains only the cells (15 million stem cells) and Arti-Cell Forte is a combination product. It actually has only 2 million cells, plus PRP. So it’s difficult to know if the healing effect is due to the cells or the PRP, or whether the two may have a synergistic effect working together,” says Koch.  

Arti-Cell Forte was acquired by Boehringer Ingelheim (a large international pharmaceutical company) last summer. “This is a boost, to know that this big company thinks stem cells and regenerative medicine have a role to play in veterinary medicine,” Koch says. 

At Cornell University a research trial studied the effect of mesenchymal stem cells on damaged cartilage in research horses. “In the follow-up, the researchers saw that the cartilage in the joints that received the cell formulation were much more preserved than the joints that did not get those cells,” Koch said. 

“I’m not sure if these therapies can turn a damaged joint into a less-damaged joint, but the Cornell study indicates that maybe we can arrest the damage and prevent further damage.” 

Every new effective treatment offers more hope for horses with damaged joints. “There’s possibility now for more consistent disease management, with joint injections, to keep a horse comfortable. It might only have to be every 6 to 8 months or even longer. It might depend on the horse, but for horses that do respond, we may be able to manage their disease more consistently and have some degree of joint disease arrest,” Koch says. This could be career-extending for some horses. 

Nominations due for Merle Wood Humanitarian Award

The time has come to nominate individuals who support our industry’s youth for the American Quarter Horse Foundation Merle Wood Humanitarian Award.

Established in 1997 in honor of the late AQHA Honorary Vice President Merle Wood, this award is designed to recognize an individual who exemplifies an ethic of meritorious kindness and benevolence in providing opportunities for all young people to be involved with the American Quarter Horse.

Nominations are due May 1.

The Merle Wood Humanitarian Award is presented each year to an individual whose outstanding voluntary service has been marked by actions or deeds that have enabled young people to experience positive opportunities and activities involving the American Quarter Horse. A multitude of service activities will be considered and is not restricted to any one type of action or deed involving youth. The award is presented each year at the AQHA convention. The 2021 AQHA Convention is February 25 – March 1 in San Antonio.

Nominees must distinguish themselves through non-compensated humanitarian endeavors. The award is not designed to honor individuals who have supported youth activities primarily through financial contributions. Previous recipients and American Quarter Horse Hall of Fame inductees are not eligible to receive this award. Awards and achievements received through industry show and/or racing competition are not a factor in the selection process.

To nominate someone for this award, please visit the Merle Wood Humanitarian Award page to submit an online application.

The Merle Wood Humanitarian award is presented by the American Quarter Horse Foundation. The award exemplifies the Foundation’s mission to connect horses and people through charitable giving in order to develop and support programs and initiatives that preserve our horse’s legacy and further the overall well being of the American Quarter Horse and the people who comprise the Quarter Horse family.

Due to the cancellation of the 2020 AQHA Convention, the 2019 and 2020 Merle Wood Humanitarian award winners will be presented at the 2021 AQHA Convention, which is scheduled for February 25 to March 1 in San Antonio.

For more information, please contact 806-378-5029 or foundation@aqha.org.

AQHA News and information is a service of the American Quarter Horse Association. For more news and information, follow @AQHA on Twitter and visit www.aqha.com/news.


Dealing with endometritis

You’ve chosen the perfect stallion, checked his history and your mare’s genetic tests are clear. The calendar is set for tracking heat cycles and your plan is sound. What could go wrong?
One relatively common issue that wreaks havoc in breeding mares is equine endometritis – an infection of the uterus that’s usually caused by bacteria such as Streptococcus, Actinomyces, Staphylococcus or Pseudomonas.

Veterinarian Rick Leone, equine reproductive specialist at Peak View Animal Hospital in Fowler, Colorado, explains that endometritis can also be due to fungal infection or an inflammatory process. “If the cervix isn’t closed, any urine or air that’s enclosed in the vaginal vault gains access to the uterus,” he said. “Loss of cervical integrity can lead to mechanical endometritis.”

Leone says endometritis is relatively common in horses, accounts for 60 to 70 percent of mares that fail to become pregnant, and can be difficult to treat. The most likely candidates for the problem are mares older than 10 to 12 years, mares in poor body condition, mares with a tipped vulva and mares with a history of having an extremely large foal that resulted in cervical damage. Mares that have had a minor tear of the vulva or vagina at foaling are also at much higher risk, and multiparous mares become more prone to endometritis.

“Wet mares, because they typically carry less body condition, are more prone to tipping of the vulva because their body condition causes the vulva to tip forward,” Leone explained. “If that happens, urine or feces can enter the cervical canal and lead to infection.”

While older mares are the most likely candidates for this reproductive challenge, Leone has seen relatively young maiden mares with raging endometritis. “Younger mares normally have a healthy uterine environment,” he said, “but it can occur at any age. If you’ve bred your mare, live cover or A.I., and she goes beyond two cycles following breeding, we consider that abnormal.”

Although it’s uncommon, mares that have never been exposed to a stallion or A.I. can be diagnosed with endometritis. “It can even occur in young mares with a completely normal cervix,” said Leone. “In many cases, such mares are treated, become pregnant and never have problems again.”

A placenta that doesn’t pass for more than one to two hours postpartum is a problem and can start to damage the uterine environment, so ensuring the complete passage of an intact placenta following birth is critical.

Mares typically have a fertility rate of about 70 percent per cycle, so it isn’t uncommon for a mare to require repeat service. However, Leone recommends a complete workup if a mare remains open after two failed breedings. “The workup includes a culture and a biopsy so we know what her uterine lining is like and if any infectious agent is present,” he said. “When mares’ uteruses are biopsied, the biopsy is sent to Colorado State University and scored 1A, 1B, 2A, 2B, 3A or 3B. 1A is ideal, and 3B is very altered and unhealthy. Fertility rates decrease with poor uterine biopsy scores, and the culture can reflect the presence of fungal agents that indicate bacteria.”

Leone explains that at the time of the culture, the veterinarian visually and manually assesses the health of the cervix. While damage to the cervix is often the result of a difficult foaling, mares without that history may have damage that prevents the cervix from closing tightly between cycles.

“If there’s a compromised cervix, we need to be aware of that,” said Leone. “We may treat systemically with antibiotics (injectable or oral), infuse the uterus with antibiotics, or use steroids or a combination of all of those treatment options to reduce inflammation and/or infection in the uterus and give the mare the best chance to maintain and carry a pregnancy once she’s bred.”

Mare owners can watch for the early clinical signs of endometritis. The first, and most obvious sign is short cycling intervals. Mares normally ovulate every 21 days and come into heat every 15 to 16 days, but if a mare comes into heat every 10 to 14 days, Leone suspects endometritis. Evidence of vulvar drainage beyond the normal few days of drainage during ovulation is also considered abnormal.

Mares with either endometritis or endometriosis typically have lower conception rates. Those that do become pregnant, which can be determined at 10 to 12 days via ultrasound, are more likely to lose the pregnancy within the first week. “They may re-cycle, and we can treat mares during the cycle they’re being bred,” said Leone. “We can even treat mares for infection a few days after breeding while we’re trying to improve the uterine environment for the embryo that’s going to come down into the uterus around day six to seven after fertilization.”

Leone says in the thoroughbred industry, which requires live cover, breeders dealing with endometritis will lavage the uterus to remove any excess fluid within a few hours after breeding. Because semen moves to and remains in the oviduct within two hours post-breeding, this measure won’t interfere with conception. The uterus can be lavaged for several days afterwards to improve the chances of a good uterine environment and successful embryo implantation.

Any mare being considered for purchase should be suspected of having endometritis if she does not have a foal at her side or isn’t confirmed pregnant.

“Be highly skeptical of any dry mare you buy,” said Leone. “If it’s a four-year old mare coming out of a performance career, that’s different. But a mare that’s been used for breeding and is not pregnant is suspect.”

Leone says a routine workup prior to the breeding season is well worth the investment. The workup includes ultrasound to check for abnormal fluid and status of the ovaries. “If the mare has no previous history of failing to get pregnant, we’ll frequently breed them one or two cycles without the expense of a workup,” said Leone. “But if there’s any concern about the mare’s ability to become pregnant, whether she had a difficult foaling, has repeated opportunity to become pregnant but hasn’t produced a foal, if she has aborted, or if she’s at risk due to conformation, we recommend a workup.”

While a pre-breeding workup costs several hundred dollars, Leone says it’s a small price to pay considering the cost of shipping semen and multiple breeding attempts.

“Endometritis is a common problem, and the risk of a mare developing it increases with age, but it’s treatable,” said Leone. “It will add expense, and the number of times you have to expose your mare to semen will go up. I tell people it’ll double breeding expenses, and they’ll have treatment expenses. If in doubt, get the workup done.”

Healthy as a… an encyclopedia of horse illnesses

It’s been said that the cheapest part of owning a horse is the purchase price. The Equine species though large and powerful, can be extremely delicate and susceptible to a myriad of problems.

VESICULAR STOMATITIS (VS): Is very contagious affecting horses, livestock, wildlife and humans. It is viral and reportable, once it’s confirmed the affected premises will be quarantined to reduce the spread of the disease, until 14 days from the onset of the last case. Blister like lesions can develop on the tongue, mouth lining, lips or nose and sometimes on the coronary bands, udder or sheath. Once suspected, a blood test is used to confirm the disease. The virus is spread by insects and direct contact.

The incubation period from exposure to first signs range from two to eight days, a fever may develop first as blisters form; one obvious sign is drooling or frothing at the mouth and not eating. The disease generally runs its course in two weeks, but may take up to two months for all the sores to heal. Live virus can be isolated from the lesions for up to a week after they first appear, during this time it is highly contagious. Soft feed may help reduce mouth discomfort, and anti-inflammatory medications used as comfort measures.

STRANGLES OR EQUINE DISTEMPER: (Streptococcus Equi): Is infectious and contagious, characterized by abscesses of the lymphoid tissue of the upper respiratory tract. It is transmissible through direct contact and fomites. It can survive up to four weeks outside the host under ideal circumstances. The incubation period is three to fourteen days and the first sign is a fever (103-106F). The horse will exhibit nasal discharge and depression, in rare cases infected horses can develop brain abscesses. Keep ill horses in a warm, dry and dust free environment. Warm compresses can help abscesses to mature and once ruptured flush with iodine for several days until discharge ceases. The attack rate is reduced by 50% in horses vaccinated.

RHINOPHEUMONITIS/ EQUINE HERPES VIRUS (EHV): nine strains of EHV have been identified worldwide, but EHV 1, 3, and 4 pose the most serious health risk for domestic horses.

EHV-1: can cause four manifestations of disease in horses, including neurological form, respiratory disease, abortion and neonatal death.

EHV-3: Causes a venereal disease called coital exanthema that affects the external genitalia but doesn’t affect fertility.

EHV-4: Causes nonfatal upper respiratory tract disease in foals and sometimes abortion and neurological disease.

EHV is a common DNA virus that occurs in horses worldwide. EHV-1 is contagious; spread by direct contact between horses and shared equipment. The virus can survive from seven days to a month in the environment. Cleaning and disinfecting everything that comes in contact with infected horses is extremely important.

After infection, the incubation period can be from 24 hours to six days or longer. EHV-1 causes a two-phase fever peaking on day one or two and again on day six or seven, often with nasal and eye discharge, but little coughing. Neurological disease appears suddenly and progresses rapidly, reaching its peak within 24 to 48 hours. Signs include: nasal discharge, incoordination, hind limb weakness, loss of tail tone, lethargy, urine dribbling, head tilt, leaning against fence or wall for balance, and inability to rise.

Diagnosis by a veterinarian includes, nasal swab and blood test to detect virus. Infected premises are quarantined for 21 to 28 days after the last new infection. Ill animals are treated with anti-inflammatory drugs and sometime IV fluids. Antibiotics can be used to treat secondary infections but they have no effect on EHV itself. The best protection is vaccination and biosecurity measures.

EQUINE ENCEPHALOMYELITIS (SLEEPING SICKNESS): There are three main strains, Eastern, Western and Venezuelan Equine Encephalomyelitis. It is caused by Alphaviruses, carried by birds and rodents and transmitted by the bite of infected mosquitoes; unvaccinated horses are the most susceptible.

Symptoms cause non-specific clinical signs and often affect the central nervous system: fever, severe depression (Sleeping Sickness), behavior changes, impaired vision, circling or head pressure, muscle twitches, inability to swallow, paralysis, convulsions and death. Supportive care is the only treatment, survival rates for horses with Eastern and Venezuelan are very low, but survival rates with Western can be as high as 70-80 percent. Vaccination is the most effective at preventing the disease, along with eliminating mosquito breeding areas.

EQUINE INFECTIOUS ANEMIA VIRUS (EIA): it is non-contagious but transmitted by blood-feeding insects, but also by blood contaminated equipment. The incubation period is 15 to 45 days or longer and progresses through three clinical phases. First signs are fever, depression and poor blood clotting, all of which are often mild and easily overlooked. This is followed by a prolonged period of recurring episodes of fever, anemia, muscle weakness and loss of condition. The intervals between episodes can range from days to months, the symptoms subside within a year but the horse becomes an inapparent carrier. The Coggins blood test is the most common testing method, seropositive horses must be quarantined and reactor horses must be euthanized or quarantined for life. Annual Coggins testing of all horses, controlling insects and good hygiene is recommended.

WEST NILE ENCEPHALOMYELITIS: Is inflammation in the brain or spinal cord. This viral disease is transmitted primarily by mosquitoes from a bird host. The infection rate in horses is low around 10 percent but the mortality rate is high around 50 percent. Symptoms include: discomfort or lameness, low-grade fever, muzzle twitching, impaired vision and lack of coordination. A blood test is necessary for diagnosis. Treatment includes supportive care and anti-inflammatory drugs. Most horses that recover will return to normal in one to six months. Preventive vaccination is the most effective.

EQUINE INFLUENZA: Is highly contagious and spreads rapidly among susceptible horses, generally ones under age five. It is rarely fatal except in weak animals. Transmission is by inhalation of respiratory secretions, with an incubation of one to three days. A high fever, clear nasal discharge, swollen lymph nodes and a dry cough. Depression, loss of appetite and weakness are often seen. The signs last less than three days in uncomplicated cases but the cough may persist for weeks. Mild cases recover in two to three weeks but severe ones may take up to six months. The diagnosis is made by testing nasal and throat secretions. Generally rest and supportive care are all that is needed, with a week of rest for every day of fever with a minimum of three weeks rest. Nonsteroidal anti-inflammatory drugs and antibiotics may be used to treat a long lasting high fever.

Prevention includes good hygiene and isolating new horses from the herd for two weeks. There are also vaccinations available, with a booster recommended every six months.

EQUINE RABIES: An acute viral infection of the nervous system. Once signs appear it is fatal. Transmission is through the bite of an infected animal, in horses the virus can be in the body for days or months before signs develop. Two major forms of rabies are seen, the “Mad Dog” syndrome: horses show rapidly developing signs of distress and extreme agitation, rolling, biting, striking, unmanageability and self-inflicted wounds.

The “Paralytic” form involves paralysis of the throat and jaw, excessive salivation and inability to swallow. People can become infected when examining the mouth or giving medication with bare hands. The only diagnosis is a laboratory analysis of the euthanized animal. Annual vaccination is the best preventive measure.

TETANUS (LOCKJAW): Is a toxic reaction to the toxin produced by the bacteria Clostridium Tetani in dead tissue, with horses and humans being the most susceptible. The bacteria is found in the soil and intestinal tracts and introduced into the body through deep puncture wounds. The incubation period varies from one day to several weeks, averaging around 10-14 days. Localized stiffness, often of the jaw and neck muscles, the hind limbs and region of the wound. General stiffness, followed by spasms and sensitivity to touch become evident. The spasms and stiffness will become worse. About 80 percent of them will die but those that survive will take two to six weeks for recovery. Supportive care and keeping in a dark stall with feed and water high enough so that they don’t have to lower the head can help. Immunization is recommended annually.

Information sourced from Merck Vet Manual at www.merckvetmanual.com

Practice Good Biosecurity to Guard Your Equine from EHM

Practice Good Biosecurity to Guard Your Equine from EHM

Please be aware Equine Herpes Myeloencephalopathy (EHM), the neurologic disease linked to Equine Herpes Virus (EHV-1), was confirmed in a Glasscock County Quarter Horse on April 16, 2019. This is the second case of EHM in Texas this year.

The positive horse attended a seven-day event at the Brazos County Expo center in Bryan, Texas starting on April 1. Following the event, the horse attended a three-day barrel racing event at the Taylor County Expo Center in Abilene, Texas starting on April 12. At that time, the expo center was also hosting a Region II high school rodeo event. The premises where the EHM positive horse originates is under quarantine and the horse is under the care of a Brazos County veterinary hospital. To learn more visit http://www.equinediseasecc.org/alerts/outbreaks.

Texas Animal Health Commission (TAHC) would like to encourage owners of horses potentially exposed to take precautions. Exposed horses should be isolated and have their temperatures monitored twice daily for at least 14 days after last known exposure. If an exposed horse develops a fever or other signs consistent with EHM, diagnostic tests may be performed. Owners should work with their veterinary practitioners to establish appropriate monitoring and diagnostic plans for any potentially exposed horse(s).

What is EHM?

Equine Herpes Myeloencephalopathy (EHM) is a neurologic disease of horses linked to the Equine Herpes Virus (EHV-1). EHV-1 in horses can cause respiratory disease, abortion, and neonatal death. Neurological signs appear as a result of damage to blood vessels in the brain and spinal cord.

EHV-1 is easily spread and usually has an incubation period between 2-10 days. Respiratory shedding of the virus generally occurs for 7-10 days, but may continue longer in infected horses. For this reason, a 21-day isolation period of confirmed positive EHM cases is suggested.

How EHM is Spread

Horse-to-horse contact, short distance aerosol transmission and contaminated hands, equipment, tack and feed all have a role in disease transmission. Direct and indirect contacts are most important for transmission since the size of the virus limits capacity for airborne transmission to distances of less than 30 feet.


Practice and enforcement of biosecurity measures on equine premises can help prevent the spread of EHV-1. Consistent biosecurity practices must be taken to reduce the risk of disease spread. For more information on biosecurity measures you can take to keep your horses healthy, visit https://www.tahc.texas.gov/news/brochures/TAHCBrochure_BiosecurityEquine.pdf.

Key to disease control is the immediate separation and isolation of identified suspect cases. Ideally, a person caring for a sick horse should not also work with healthy horses. If this is impractical, always handle healthy horses first and sick horses last.

People can easily transmit this virus on their hands and clothing. Individuals should wash their hands thoroughly with soap and hot water between contacts with horses to reduce risks of disease spread. Wearing disposable gloves and changing them between horses or use of hand sanitizers between horse contacts are other alternatives. When handling any sick horses suspected to have EHV-1 infection, it is imperative that halters, bridles, and other tack not be shared with stablemates. Feed and water buckets should also be dedicated to sick horses and not shared within a stable.


Herpes viruses can be treated by many disinfectants. A 1:10 dilution of bleach in water is effective against EHV-1. All areas must be thoroughly cleaned of dirt, plants, and animal waste before the use of these products. Use soaps or detergents to clean the area before applying a disinfectant.

In barn environments, where organic material (dirt, plants, animal waste, etc.) cannot be completely removed, it is suggested to use a disinfectant that retains activity in the presence of organic matter. Phenolics, such as 1 Stroke Environ® or SynPhenol-3®, and accelerated hydrogen peroxide products, such as Accel®, have this property. Be sure to follow manufacturers’ recommendations and label instructions for all disinfectants.

*TAHC does not endorse any of the listed disinfectant products.

Additional Resources:



–Texas Animal Health Commission

Neurologic form of EHV-1 confirmed in Montgomery County horse

AUSTIN – Equine Herpes Myeloencephalopathy (EHM), the neurologic disease linked to Equine Herpes Virus (EHV-1), was confirmed in a Montgomery County reining Quarter Horse on April 9, 2019.

The positive horse attended a reining event in Ardmore, Oklahoma the week of March 18. TAHC staff has been in contact with the Oklahoma State Veterinarian to ensure event participants were notified and enhanced biosecurity measures are taken.

Since the Oklahoma event, the horse has not traveled to any other event and is under the care of a Brazos County veterinary hospital. The horse was quarantined after showing signs of ataxia and other neurologic signs consistent with EHM.

While the risk of exposure to the virus was likely low at the event, owners of horses potentially exposed are encouraged to take precautions. Exposed horses should be isolated and have their temperatures monitored twice daily for at least 14 days after last known exposure. If an exposed horse develops a fever or other signs consistent with EHM, diagnostic tests may be performed. Owners should work with their veterinary practitioners to establish appropriate monitoring and diagnostic plans for any potentially exposed horse(s). For more information on biosecurity measures you can take to keep your horses healthy, visit http://www.tahc.texas.gov/news/brochures/TAHCBrochure_BiosecurityEquine.pdf.

One of the most common clinical signs of EHV-1 is fever, which often precedes the development of other signs. Respiratory signs include coughing and nasal discharge. Neurologic signs associated with EHM are highly variable, but often the hindquarters are most severely affected. Horses with EHM may appear weak and uncoordinated, urine dribbling and loss of tail tone may also be seen. Severely affected horses may become unable to rise. For more information on EHM visit http://www.tahc.texas.gov/news/brochures/TAHCBrochure_EquineHerpesMyeloencephalopathy.pdf.

It is important to remember these signs are not specific to EHM and diagnostic testing is required to confirm EHV-1 infection. Many horses exposed to EHV-1 never develop clinical signs. If you suspect your horse has been exposed to EHV-1, contact your local veterinarian.

The equine industry is encouraged to obtain the latest information on this outbreak and other disease events across the country by visiting the Equine Disease Communication Center (EDCC) website, http://www.equinediseasecc.org/alerts/outbreaks. Additional Texas EHM cases will be posted on the EDCC.

–Texas Animal Health Commission

EHV-1 infected horse reported in Johnson County

Laboratory confirmation of a Johnson County horse infected with Equine Herpesvirus neurologic disease, or Equine Herpes Myeloencephalopathy (EHM), was received by Wyoming Livestock Board (WLSB) staff veterinarians on Thursday, April 4. The horse has been quarantined to its premise in Johnson County with 19 other horses.

The affected horse began showing neurologic signs, including hind-end weakness, on Wednesday, April 3. It is not known where this horse contracted the disease, but it had been at college rodeo events on March 15-16 at the Cam-plex in Gillette and March 21-24 at the Goshen County Fairgrounds in Torrington.

Dr. Thach Winslow, Wyoming assistant state veterinarian for field operations, said that any horses that were at these events should be considered potentially exposed, and owners should consider taking preventative measures, including close monitoring of the horses and checking their temperatures at least twice daily. If any of these horses show neurologic signs or fever, the owner needs to isolate them and contact his/her veterinarian for advice and treatment options.

According to WLSB staff veterinarians, equine herpesviruses are very common DNA viruses in horse populations worldwide. The great majority of horses are exposed to EHV1 – the virus that causes EHM – early in life and will become life-long latently infected, meaning they will show no external signs of illness. However, the virus can be reactivated during times of stress such as strenuous exercise, over-exertion, long-distance transport, or at weaning.

Horses with neurological disease caused by EHV1 infection can soon become uncoordinated and weak and have difficulty standing, urinating, and/or defecating. Often the rear limbs are more severely affected than the front. Signs of brain dysfunction may occur as well, including extreme lethargy and a coma-like state. The disease is contagious and can be spread by direct horse-to- horse contact; by contaminated hands, equipment, and/or tack; and, for a short time, through aerosol dissemination within the environment of the stall and stable.

There has been a marked increase in the number of EHV1/EHM cases in the U.S. in recent years. In the last 30 days, cases have been reported at large horse facilities and events in several states including Idaho, Arizona, Nevada and California. Owners who plan on taking their horses to such facilities and events can help prevent spread of the disease by practicing proper biosecurity measures. This includes not sharing equipment such as water/feed buckets and tack. They should also isolate their horses if they suspect them of being sick, and not allow them to leave the premise until cleared by a veterinarian.

More information on Equine Herpes Virus can be obtained by contacting the Wyoming Livestock Board Field Office at 307-857-4140.

–Wyoming Livestock Board

State veterinarian orders quarantine on horse facility in Clark County

Horses at Nevada State High School Rodeo in Pahrump may have been exposed to upper respiratory and neurological disease

(LAS VEGAS, Nev.) – One positive case of equine herpes virus type 1 (EHV-1) with neurologic signs has been reported in Clark County, and the Nevada Department of Agriculture State Veterinarian Dr. JJ Goicoechea has ordered a quarantine. There is no public health risk, therefore, details about the facility will not be released per NRS 571.160.

“I have issued this quarantine to help prevent the spread of disease during equine event season in Nevada and surrounding states,” Dr. Goicoechea said. “Equine Herpes Virus-1 can cause respiratory disease in young horses, abortions in pregnant mares and neurologic disease in older horses.”

Horses at the Nevada State Junior/High School Rodeo that took place Feb. 22-24 in Pahrump may have been exposed and should be monitored for signs of disease, such as fever, cough or runny nose.

The average incubation period for EHV-1 is four to seven days, but some may take up to 14 days. Eight to 12 days after infection first appears, neurological disease may occur.

EHV-1 is a reportable disease, meaning when veterinarians diagnose it, they are required to notify the Nevada Department of Agriculture, per NRS 571.160. A list of reportable diseases can be found at agri.nv.gov.

State veterinarian says: monitor horses, practice biosecurity

“I urge all horse owners to monitor their horses closely, taking temperatures twice daily and seeking veterinarian care for any fevers over 102 degrees,” Dr. Goicoechea said. “It is especially important to practice biosecurity to minimize the risk of spreading disease.”

Biosecurity means doing everything possible to reduce chances of an infectious disease being transferred by people, animals, equipment or vehicles. EHV-1 and other diseases can be easily transferred on boots, coats, gloves and equipment. Some basic practices include:

Never share equipment between horses, and always wear clean clothes when going from ill horses to others.

Always start chores at healthy horses, and end with sick or recovering (within 30 days) horses.

Avoid common areas such as hitching rails, wash racks, etc. during an outbreak.

–Nevada Department of Agriculture

Nevada state vet asks horse owners to travel with caution

(LAS VEGAS, Nev.) – After two positive confirmations of streptococcus equi bacterial infection (commonly known as strangles or equine distemper) and several more likely positives on one property in Clark County, Dr. JJ Goicoechea, state veterinarian for the Nevada Department of Agriculture (NDA), stresses the importance of best biosecurity practices to minimize the risk of spreading disease.

“To date, only one facility is affected, and I have recommended a 21-day hold – no horses in or out of that facility, beginning Feb. 20, to slow the spread of disease,” Dr. Goicoechea said.

Per Nevada Revised Statute (NRS) Chapter 571.160, details regarding animal disease reports must be kept confidential unless there is a public health risk. Because strangles cannot be transferred from horses to humans, there is no such risk at this time.

“It is not uncommon to see cases of upper respiratory diseases in horses this time of year, and we notify local veterinarians and associations when we have new cases,” Dr. Goicoechea said. “We haven’t issued any quarantine orders, but our primary focus is stopping the spread of disease, especially as we approach horse show and event season in the west.”

Biosecurity means doing everything possible to reduce chances of an infectious disease being transferred by people, animals, equipment or vehicles. The bacteria that causes strangles is easily transferred on boots, coats, gloves and equipment. Some basic practices include:

Never share equipment between horses, and always wear clean clothes when going from ill horses to others.

Always start chores at healthy horses, and end with sick or recovering (within 30 days) horses.

Avoid common areas such as hitching rails, wash racks, etc. during an outbreak.

“Please monitor your horses for symptoms including a cough or runny nose and consult with your veterinarian to ensure vaccinations are current,” Dr. Goicoechea said. “If you suspect your horse may be exhibiting signs of illness, contact your veterinarian and do not allow contact with other horses.”

Per NRS Chapter 571.160, any animal owner or practicing veterinarian who has knowledge of a confirmed case of a reportable disease, shall immediately notify the NDA Animal Disease Laboratory. A list of reportable diseases can be found at agri.nv.gov.

The Nevada Department of Agriculture (NDA) promotes a business climate that is fair, economically viable and encourages a sustainable environment that serves to protect food, fiber and human health and safety through effective service and education. The NDA includes the divisions of Administration, Animal Industry, Consumer Equitability, Food and Nutrition and Plant Industry.

–Nevada Department of Agriculture

Be sure your horse is hydrated

It’s like clockwork. When Stacy Tarr, DVM, brings his 20-year-old gelding up to take care of his recurring lameness, the old horse will drink one full tub of water every night.

“If I come out and there is more than an inch of water in that tub, that’s unusual,” Tarr said, and the veterinarian takes note.

Water consumption is crucial to good health, and changes in it often signal other health problems.

“You need to know how much water your horse normally drinks,” Tarr said. “The exact amount is going to vary between summer and winter, but it is pretty consistent.”

Winter weather often compounds the task of physically getting water to your horse, as well as getting your horse to drink water, especially in freezing conditions.

“What I worry about over the winter is that in order to maintain their body heat, horses have to eat more roughage,” Tarr said. “That’s how their internal furnace works: the hay and roughage they eat ferments and creates body heat. They are eating more to stay warm.

“But horses often don’t drink enough when it gets cold,” he added. “Eating more roughage and not consuming as much water leads to dehydration and impaction-caused colics.”

Impaction colic caused by dehydration can happen over several days or weeks, especially if a horse is chronically not drinking enough water.

“That’s my biggest concern in winter,” Tarr said. “The best prevention is to know your horse and how much water he drinks.”

Avoid Dehydration

Experts vary on what constitutes a normal range of adequate water intake for the average horse. Depending on size and individual metabolism, normal consumption for a mature horse can range from six to 12 gallons per day.

“It can be hard to tell whether or not your horse is getting enough to drink,” Tarr said, “especially if he is watering out of a creek or a lake, or if you use automatic waterers.”

Manure consistency is variable and, in Tarr’s experience, is not a good indicator of dehydration. One basic way to test if a horse is dehydrated is to check skin turgor, or firmness.

“If you gently pinch the loose skin below the eye or on the neck, in a couple of seconds the skin should flatten right back out again,” he explained. “That indicates good turgor and adequate water content. If the skin stays tented up or pinched, it’s because the horse is dehydrated.

“However, the only way to confirm how dehydrated a horse might be is to draw blood and do a packed cell volume test and check the red blood cell count in the blood. If it’s too concentrated, it’s because he doesn’t have enough fluid in his blood circulation.”

Encourage Consumption

Horses must have constant access to fresh water, Tarr said. Drinking water that is close to freezing temperature also reduces a horse’s core body temperature.

“When it’s cold out, if the water is warmer, horses drink more,” Tarr said. “If they drink from a [freezing] water tank, they just don’t get as much.”

Research at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center proved it in 1994. Its herd of feral ponies drank 40 percent more heated water when offered a choice between that and near-freezing water. The study showed that ideal water temperature is between 40 and 65 degrees Fahrenheit.

Heating options include automatic waterers with built-in heaters; however, like watering from a creek or lake, they don’t allow you to monitor how much water your horse is actually drinking like a bucket or a trough would. In addition, automatic waterers still need to be checked daily to make sure they are running and not freezing over. Floating tank heaters and models that sit on the bottom of the tank are options, but those types of heaters need to be regularly checked for electrical problems, too. The researchers at New Bolton Center found that carrying out buckets of heated water was the easiest way to get it to their feral herd.

Regardless of the method, keep the water fresh, Tarr said.

“Bigger tanks will freeze less than a smaller one,” he said. “Our tanks are of the size where horses drink it down, so [the tanks] don’t get stagnant and fill with ice. We fill our [200- to 250-gallon] tanks twice a day.

“It’s best to heat the water if you can. If not, keep a sharp shovel handy.”

–Quarter Horse News