Since March, twenty-two Equine Herpes Virus (EHV-1) outbreaks involving at least 200 horses, predominantly sport horses like Thoroughbreds and Trotters have been reported in France, in the Great West , but also in Ile-de-France, in the east and in the Gironde, according to the Reseau d’Epidemio-Surveillance en Pathologie Equine (RESPE) (computer translated).
However, all the cases are not reported to the RESPE and with the information gathered, the actual numbers are likely underreported.
Officials say the situation seems to be stabilizing with no new outbreak confirmed since Apr. 27.
Many competitions were cancelled because of the outbreaks.
RESPE notes that in general, the wide vaccination of the population with a booster every 6 months is strongly recommended in France where the virus circulates each year.
EHV-1 infection in horses can cause respiratory disease, abortion in mares, neonatal foal death and neurological disease. The neurological form of the disease is known as Equine Herpes Myeloencephalopathy (EHM) and may be caused by damage to blood vessels of the brain and spinal cord associated with EHV-1 infection. EHM is most often due to the neuropathogenic strain of EHV-1, but may occasionally be caused by the non-neuropathogenic strain of the virus.
EHV-1 is easily spread and typically has an incubation period between 2-10 days. Respiratory shedding of the virus generally occurs for 7-10 days, but may persist longer in infected horses. For this reason, a twenty-one day isolation period of confirmed positive EHM cases is recommended along with stringent biosecurity protocols. Similar to herpes viruses in other species, the latent form of EHV-1 can reactivate at a later date, but generally with a low viral load posing a low risk of infecting other horses. Humans are not at risk of contracting the virus, however humans can act as an indirect mode of transmission.