Equine Herpes Virus

Herpes Virus

Seen primarily in young horses. Majority run a mild respiratory disease. 80-90% of horses are exposed by 2 years old, lays latent in the trigeminal nerve.

EHV-4

Favorable prognosis, more common from mild respiratory disease. Only affects epithelial cells.

EHV-1

More virulent. Can cause abortion, neurological disorders, neonatal death, ocular disease, and death along with respiratory problems.

Epidemiology

Reservoir is latently infected horses. Lives in environment for 7 days, easily inactivated by heat and disinfectants. Most adult horses have been exposed, especially from their mothers. Can be spread by direct and indirect contact.

Outbreak Risk Factors

Overcrowding, heavy parasite burden, poor nutrition, stress, concurrent disease, climate. Very contagious, morbidity can reach 100%.

Latency

EHV lives in trigeminal ganglia, causing periodic shedding of virus caused by stressors. Not accompanied by any respiratory clinical signs. EHV-1 reactivation can cause abortion.

Pathogensis

EHV-1 and 4 replicate in upper respiratory tract. EHV-1 is more aggressive, reaches bloodstream and spreads, causes late term abortion and ischemia. Opportunistic bacterial pneumonia in both cases.

Clinical signs

Mild respiratory disease, biphasic fever, nasal and ocular discharge. Older or previously exposed animals are milder or show no signs. 10 day incubation period.

Diagnosis

Nasal swab, spinal tap, serology. Hard to detect in latently infected horses

Treatment

NSAIDS for fever, maybe antibiotics and fluids.

Vaccination

Broodmares get specific high antigenic vaccines so they dont abort foals. Other horses get rhimopneumonitis combo vaccine for milder cases. Dont prevent disease but diminish shedding.

Equine herpes myeloencephalytis

Genetic variant of EHV-1, associated with neurologic disease. Not currently any specific management advice. No vaccine currently, but other herpes virus vaccines can help to limit nasal shedding of this version.

Management

Keep stress low, don’t mix age groups, clean,