EHV1 INFECTION AND VACCINATION
EHV1 Equine Herpes Virus 1, also called Rhino, is an equine respiratory virus. It can also cause severe neurologic disease or abortion. It is transmitted airborne by horse, contaminated feed, water, stall cleaning utensils, or people’s hands and clothes. Exposure to the aborted fetus and placenta can transmit the EHV1 virus.
SIGNS
Signs are fever (temperature greater than 101.5), snotty nose, eye drainage, cough, depressed, off feed, and swollen legs. The neurologic form signs are incoordination, ataxia, dog sitting, trouble or inability to get up.
NEW RESEARCH
New research has shown when the horse develops the EHV1 disease it is the amount of EHV1 virus in the body that causes the various signs and severity. Horses with a low amount of the virus, are mildly sick with nasal and eye discharge, off feed, and droopy. If there is a moderate amount of virus, then the horse is sick with a 102+ fever, a snotty nose, cough, is depressed, and has swollen legs.
A high amount of virus in the body means the virus has multiplied out of control, overwhelming the horse. In this case the horse gets and exhibits the neurologic form of EHV1.
EHVI NEUROLIGIC CASES
These horses are highly contagious. They are full of virus that shed airborne out of their nose, contaminating the barn and their handlers. When there is the neurologic EHV1 outbreak, the premise and barn are quarantined until the virus and infection is under control. The neurologic form is RARE. When it occurs, it is usually at a place of competition such as a horse show or race track where many are housed in close quarters. The competition stresses the horse, which lowers its immune system, making it vulnerable to the virus. Outbreaks have also happened at boarding barns.
TREATMENT
The respiratory form of EHV1 is treated with drugs to lower the fever and later, antibiotics for very snotty nasal discharge or chronic cough. Treatment for the neurologic form is isolation and virus testing, anti-inflammatory drugs, supportive care and prayer.
PREVENTION
Most horses should be given the EHV1 (Rhino) vaccination 2 times a year. Competition horses should be vaccinated 4 times a year. The 7-way combo vaccine given in the spring contains Rhino, Eastern &Western Encephalitis, West Nile, Tetanus, and Flu. In the fall, a Rhino/Flu combo vaccine is given. Pregnant mares are given a Rhino vaccine (Pneumabort) the 5th, 7th and 9th month of pregnancy. It takes 2 weeks after vaccination for the horse to build antibodies and be protected. Weanlings get vaccinated at 4-5 months and a booster 4 weeks later. It is not recommended to vaccinate at weaning time because the baby is stressed and its immune system is lowered which can lead to illness. Vaccinate 1 month before or 1 month after weaning.
EHV RISK EVALUATION ASSAY TEST
There is now a test that can measure the amount of EHV1 IGG4/7 antibodies in the horse to evaluate the risk of infection and likelihood of EHV1 disease. A high level of IGG4/7, means the horse has a high level of protection and low risk for EHV1 disease. If it has a low level of IGG4/7, it has a high risk for EHV1 disease. A low-level result means it’s immune system did not respond to the vaccination or it has been too long since vaccinating so the horse is vulnerable.
STRANGLES TEST
There is also a Strangles IGG antibody test which can measure the amount of strangles antibodies the horse has post infection or post vaccination. If the titer is high, the horse is protected and doesn’t need an annual strangles vaccination.
REACTIONS
Vaccine reactions are rare but do occur. Reaction signs are hives or colic in a few hours, mild fever, droopy, sore neck at injection site in a day, or abscess at injection site or purpura in a week. IF the horse is sensitive to vaccines, we usually don’t give a 7-way combo vaccine. Individual vaccines (EWT, West Nile, Flu Rhino) are given separately, 1 week apart. To prevent vaccine reaction, Banamine or Dex premedication can be given 4+ hours before vaccination. Zyrtec can be given the night before and in the morning of vaccinating. The manufacturers of the vaccines; BI, Merck, Zoetis all have a vaccine guarantee and will pay for vaccine reaction treatment.
CASTRATION SIGNS: September 10-17
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