11/19/2025
Because of the EHV-1 outbreak in Texas we are implementing a NO HORSES IN, NO HORSES OUT policy until further notice.
EHV-1 boosters will be given tomorrow to every horse at the ranch.
Habitat for Horses Article on EHV-1
Signs, Symptoms and Transmission
The signs the occur with EHV-1 and the EHM strain include things such as decreased coordination, urine dribbling, fever, hind limb weakness, leaning against things to maintain balance, lethargy and the inability to get off the ground. More signs of the infection of this virus include depression, anorexia , nasal and ocular discharges. Fever is the most common clinical sign of EHV-1, some horses that appear perfectly healthy can still spread the virus from nostril secretions and also from secretions from coughing. Horses or humans that have been in contact with aborted fetuses, fetal fluids and placentae can easily spread the virus. When a human walks through secretions or walks in fetal fluid and gets it on their boots it will be transmitted to wherever they walk. It is extremely easily transmissible. Most mature horses build some type of immunity through repeated natural exposure, but will not build immunity to the EHM strain.
Risk Factors
There is a strong correlation between the risk factors and infected horses. The main risk factors that are directly related to EHV-1 include age, confined vs pasture, higher traffic of people and horses in and out of stables, use of common equipment, training and competition, the s*x of the horse, the gender and even what season it is. Horses that are stabled are more prone to EHV-1 because of stress, those in pastures have less stress. Older horses have a higher susceptibility, and during the time of winter and spring are all risk factors. The horses past exposure has a huge increase in risk factor, transporting and hauling frequently also increases the risk.
Diagnosis, treatment and prevention
Treatment
The current diagnosis for EHV-1 is PCR, polymerase chain reaction, which copies the DNA so once can see if a virus is in the DNA segment. PCR can detect the viral load in the DNA, telling if the horse is very infected or below detection levels. To get samples for PCR a veterinarian may want to have an uncoagulated blood sample and also a nasal swab. There are a few downfalls of PCR one being that it is very time consuming and takes a while to get back samples and results and the other downfall is how the results are interpreted. Horses can have a latent virus but not show clinical signs and be called clinically normal, except the PCR results will give positive test result when it’s not so straightforward The one other downfall of PCR is that there is not standardized protocols between the laboratories. Treatment for EHV-1 is limited at the time and there isn’t one definitive treatment that is guaranteed to work. The treatments now include intravenous fluids, I.V’s, or anti-inflammatory drugs.
Prevention
Vaccines exist to control the virus but not to prevent it. The inactivated vaccine contain a low antigen load and are made to help protect against the respiratory symptoms, the performance of the inactivated vaccines is variable are doesn’t work for all. The modified live vaccine is made to vaccinate healthy horses 3 months or older, to help prevent the respiratory symptoms caused by EHV-1. Vaccinations should be given in 6-month intervals, and different horses will need to be vaccinated at different times. Pregnant mares should be vaccinated during the fifth, seventh and ninth months of gestation, with the inactivated EHV-1 vaccine. Foals should be vaccinated in a series of 3 doses starting at 3 months in 4–6 week intervals. Even though a horse has been vaccinated, infection and clinical disease still continues to occur. New vaccines to help prevent the spread of the virus are being studied.
To prevent the spread of EHV-1 there are a few steps that should be taken. The main things to be done are to stop horse movement and transportation, do not allow horses that have been exposed to EHV-1 to be in contact with unexposed horses, and isolate ones that are showing symptoms of the virus. Ideally horses who are showing symptoms should be completely quarantined. The recommend amount of days a horse should be quarantined is at least 21 days. Another main part of preventing EHV-1 from spreading is to be aware and careful of sharing equipment and spreading via human contact to horses. Since people can and do transfer this virus via their hands and clothing, people need to take sanitary precautions when handling a sick horse. Disinfecting footwear and wearing gloves can help minimize the risk of spreading. Not only disinfection footwear but also routinely cleaning and disinfecting the barns and buildings where horses have been. In the case of an outbreak one should take precaution have try to minimize stress on the horses, as stated previously stress can trigger a latent virus to reactivate or it can allow a horse to be more easily infected.o
