Equine Herpesvirus-1: Mutant Strain an Emerging Problem

Scientists from the Gluck Equine Research Center and the Livestock Disease Diagnostic Center at the University of Kentucky recently reported that a particular mutant form of equine herpesvirus-1 (EHV-1) that causes myeloencephalopathy (a degenerative disease of the brain and spinal cord) in horses has the potential to pose serious health and economic threats to the North American horse industry.

Like other herpes viruses, EHV-1, including the encephalopathy-causing mutant strain, can lay dormant in previously infected horses.

"Latently infected horses are at risk for re-activation of the dormant mutant virus and can serve as a virus reservoir to potentially infect other horses," explained George Allen, PhD, a professor at the University of Kentucky and a co-author on the study.

Since EHV-1 myeloencephalopathy is currently considered a potentially emerging disease, this study was designed to determine the prevalence of the mutant EHV-1 in the Thoroughbred broodmare population in central Kentucky.

DNA was extracted from submandibular lymph nodes from 132 broodmares and was analyzed by a polymerase chain reaction (PCR) test to determine if EHV-1 and/or mutant EHV-1 were present.

"Over half of the horses examined were latently infected with EHV-1, and 18% of these horses harbored the mutant form of EHV-1 that causes myeloencephalopathy," said Allen.

These results show that the mutant strain of EHV-1 has already become established in Central Kentucky horses. Considering that EHV-1 neurological disease is most common where large numbers of horses are stabled together, the spread of this virus via latently infected horses is becoming an important consideration.

Further research on preventative and therapeutic strategies for control of the EHV-1 neurologic disease is clearly warranted.

The study, "Prevalence of latent neuropathogenic equine herpesvirus-1 in the Thoroughbred broodmare population of central Kentucky" will be published in an upcoming edition of the Equine Veterinary Journal. Additional information is available at articles #9689  and #9378.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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