Newsdate: Thursday February 16, 2023 - 11:00 am
Location: WASHINGTON, DC

A Quarter Horse in Hood County, Texas, has tested positive for EHM. The horse was tested after developing neurologic signs, including poor muscle control in the hind limbs. The local veterinary clinic immediately placed the horse under official quarantine, where it remains throughout treatment. The premises of origin has also been quarantined.

Horse confined in a stall

Horses with EHM usually have a fever at the onset of the disease and might show signs of a respiratory infection and a few days later, neurologic signs such as ataxia (incoordination) are apparent.
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The Texas Animal Health Commission is working with the owner and local veterinarian to monitor other horses and enforce biosecurity measures on the premises. The affected horse attended the National Western Stock Show rodeo event in Denver, Colorado, on January 20-21. It returned to the premises following the event and has not visited any other events. The Colorado State Veterinarian has been contacted about this case.

This is the first positive detection of EHM in Texas this year.

EHM in Massachusetts

In addition, a horse in Hampshire County, Massachusetts, has tested positive for EHM. Three other cases are suspected. The Massachusetts Department of Agricultural Resources is working with the entities involved to limit the spread of disease. Currently, it is unknown how many horses are exposed.

Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares and EHM.

In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression and a nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months) but can be earlier. Abortions can occur anywhere from two weeks to several months following infection with EHV-1.

Horses with EHM usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone and recumbency (inability to rise) develop.

Herpesvirus is easily spread by nose-to-nose or close contact with an infectious horse; sharing contaminated equipment including bits, buckets and towels; or clothing, hands or equipment of people who have recently had contact with an infectious horse. Routine biosecurity measures, including hygiene and basic cleaning and disinfection practices, should be in place at all times to help prevent disease spread.

Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread, and the best method of disease control is disease prevention.

Press release by EDCC Health Watch brought to you by Boehringer Ingelheim