GETTING it STRAIGHT

 

EVA, EHV, EIA and EPM—

Knowing and recognizing the differences between these equine ailments

Part 1 of 2 EVA and EHV

 

By Kimberly A. Rinker

 

“Horses should be vaccinated on a regular basis against potential diseases. EHV-1 has been identified as a growing problem.” —William Hope, Community Practice Equine Clinic Veterinarian, Purdue University School of Veterinary Medicine Purdue file photo/Mike Kerper

It can be overwhelming: EVA, EHV, EIA and EPM. All are similarly named and some have similar symptoms. What’s a horse trainer to do?

Once these diseases are defined, it can become a little easier to recognize their symptoms and develop a sound program for treatment and prevention.

“The key is to establish a sound vaccination program,” said Dr. Martin Allen, DVM, MS, University of Illinois, College of Veterinary Medicine. “Of course, good nursing and follow-up care is imperative as well.”

The first of our two-part series covers EVA and EHV. Midwest Thoroughbred provides a brief synopsis of each disease, information on the symptoms, and a look at what actions horsemen can take to prevent and/or treat these ailments.

EVA

What It Is: Equine Viral Arteritis is primarily a sexually transmitted virus best known for causing abortion in pregnant mares. It can be transmitted, however, through nasal discharge, and is the only virus identified as testosterone-dependent, and therefore is limited to harboring in stallions. It was first discovered in 1953 in an Ohio-based Standardbred.

“We rarely see this disease in the racehorse community,” said Dr. Pete Langley, DVM, a practicing, Chicago-based equine veterinarian. “You’re much more likely to find cases of EVA on the breeding farms, but even then, it much less prevalent now than it was 20 years ago.”

A colt who has been exposed to the disease prior to puberty will not carry enough testosterone in his system to become a carrier and thus, a shedder. Veterinarians recommend vaccinating all colts at six months of age as a preventative measure.

If a mare has been exposed, she will carry the disease in her system for only a short period (24-48 hours), but during that time can infect other horses around her. EVA has been known to eliminate entire breeding programs by causing a high number of mares in close proximity to each other to abort.

EVA poses risks for the breeding industry that continue to grow on an international level. U.S.-based horses who have tested positive for EVA antibodies, as well as semen obtained from EVA-infected horses are likely to be barred from being exported, or imported into foreign countries.

“EVA really becomes an issue when horses are going to be exported,” Dr. Langley explained. “It’s tough because there are not a lot of people who routinely vaccinate for EVA. If an EVA outbreak is suspected—say in a breeding farm locale—then veterinarians will pull blood, and will utilize either a DNA-test, a virus isolator, or both.”

Symptoms: High fever and swelling of the legs, genitals and eye areas and loss of appetite, along with nasal discharge, are typical signs of EVA. The swelling is due to inflammation of the arteries. In extremely rare cases EVA can end the racing career of a horse and even lead to death.

Treatment: EVA can be confirmed through a blood test. Annual vaccinations are the best treatment for preventative maintenance. Veterinarians recommend vaccinating foals at six months of age, with the vaccination being especially important in male horses who have not yet reached puberty.

The Skinny: The good news is that a high percentage of racehorses in North America carry the antibodies in their system to combat EVA. Mares, geldings and sexually immature stallions typically acquire the disease, and after a shedding phase become immune. Stallions can become carriers due to the testosterone-dependant nature of the virus, however, and harbor it in their systems for weeks, months and even for the lifetime of the animal.

What You Can Do: If you have broodmares who have been exposed to EVA, they need to be separated from other horses immediately and quarantine measures taken to curtail the possible spread of the disease. All horses in your care should then be tested.

The American Association of Equine Practitioners also provides an EVA informational brochure that can be downloaded at www.AAEP.org.

EHV-1 through 5

What it is: Equine Herpes virus is a group of nine viruses that can cause serious problems in horses and other related species, with five specific types noted by veterinarians that affect domesticated horses. The other four types of EHV (EHV-6, -7, -8, and -9) affect only donkeys, zebras, Przewalski’s horses and the Asiatic wild ass.

Of EHV-1,-2,-3,-4 and -5, only EHV-1, EHV-3 and EHV-4 commonly cause serious distress. These diseases are not transferable from human to horses, or vice versa.

EHV-1, which has been the subject of much concern due to a number of outbreaks throughout the country recently, is the most serious. It causes abortion in mares, respiratory infection and neurological troubles. It is highly contagious and can be spread by the co-mingling of horses, through the sharing of buckets and tack, and environmentally in a stable or stall, as well as through the air—albeit for a short time.

EHV-2 causes respiratory issues in horses, such as coughing, conjunctivitis and swollen lymph glands, and is found in the upper airways of nearly all foals. It, in itself, is rarely fatal. However, it can suppress a foal’s immune system, therefore setting it up for other infections which could prove troublesome or fatal.

EHV-3 is spread through direct and sexual contact between horses, and through flies carrying infected vaginal discharge. It can cause ulcerations to occur on the genital areas of horses, as well as negatively affecting a stallion’s libido. Horses with EHV-3 often experience a loss of pigment on black skin in the genital region. EHV-3 is rare, and is not fatal, but it can severely affect a breeding operation if a herd is infected. There is no treatment, but the virus has a short life (10 days to two weeks).

EHV-4 causes upper respiratory issues in younger horses—usually foals to 3-year-olds—and is not fatal. Aged horses generally develop immunity to EHV-4.

EHV-5 is very similar to EHV-2, causing non-fatal, upper airway ailments in young foals.

Symptoms: EHV-1 & EVH-4 generally produce symptoms of a high fever, along with nasal discharge and/or coughing. If left untreated many EHV-1 infected horses will become uncoordinated and have trouble walking, and some will have difficulty urinating. Horses will also often appear lethargic and depressed. After the initial fever, the neurological signs may appear within the next eight days. Once infected, horses carry the virus in their system for life, in a dormant state. Symptoms can reoccur later in life due to stress.

“Nowadays, we mainly see the respiratory forms of EHV-1,” Dr. Moffett stressed. “It’s important to vaccinate your horses and work at keeping their immune systems up. This is definitely a problem that doesn’t want to go away.”

Treatment: Initial treatment includes lowering the temperature of the horse and isolation, to determine the cause of the symptoms, and, if possible, to pinpoint the spot of contamination.

“EHV-1 & EHV-4 both have a short environmental life span, but isolation of the horse and disinfection of the premises is paramount to help prevent further spread of the diseases,” Dr. Allen stated.

“The Chicago outbreak that occurred in 2007 at Balmoral Park could have been devastating to the racehorse population there, but it wasn’t,” Dr. Langley noted. “The main reason is because of the excellent job that was initiated by the trainer (Nelson Willis), and veterinarians Dr. David Fitzpatrick and Dr. Jeremy Owens. Their actions were textbook perfect in terms of how an outbreak of EHV-1 should be handled. Dr. Owens was right on top of things the day the disease broke, and Willis had his barn quarantined immediately. According to reports I have from around the country, this case had the least amount of contamination, due to the quick response from the affected trainer and the attending veterinarians.”

The Skinny: Equine Herpes viruses can exist and survive on almost any inanimate object—feed tubs, water buckets, bridles, saddles, clothing, shoes, hair, tires, etc.—for up to three days. Therefore, it becomes imperative for trainers to disinfect and sanitize equipment and areas frequented by a large number of transient horses.

“It seems that there is a specific mutation of EHV-1 which causes the neurological troubles,” Dr. Langley said. “The respiratory part of the disease is much easier to fix.”

A veterinarian can perform a nasal swab and blood sampling for testing of Equine Herpes viruses.

What You Can Do: All horses housed on the backsides of racetracks, training centers, farms, and sale barns—in short, anywhere there is a large influx of transient horse populations—should be vaccinated for Equine Herpes virus every three to six months, along with an Equine Influenza Virus vaccine as a booster. Also, trainers should never share or switch equipment—even between their own horses. If you suspect you have housed or shipped an EHV-positive horse, disinfecting barns, stalls and trailers with a mixture (one part chlorine bleach and ten parts water) is imperative.

“I think that outbreak in Chicago really woke a lot of folks up,” Dr. Langley added. “It definitely has made them more cognizant in terms of not co-mingling water buckets, rigging equipment, feed tubs and the like.”

Conclusion

With any serious ailment affecting your horse, it often pays off in the end to get your veterinarian involved from the start. Let them assess the needs of your horse in relation to what disease/infection/virus is troubling them at the time, and then work together with he or she to do what is best for the animal in terms of treatment, recovery, maintenance and future prevention.  

For more information

Contact the U.S. Department of Agriculture (USDA), and Animal and Plant Health Inspection Services (APHIS), Veterinary Services National Center for Animal Health Programs, at 4700 River Road, Unit 46, Riverdale, MD 20737–1231, Telephone 301-734–3279, Fax: 301- 734–7974 or visit www.aphis.usda.gov/vs/ceah/.

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