According to the Equine Disease Communication Center a number of horses have been affected by Equine Herpes viruses during the months of March and April 2016, in Pennslvania.
Respiratory distress as a symptom of equine herpes virus infection
Equine herpes virus infections in horses, such as those in Pennsylvania, can cause respiratory disease, abortion in mares, neonatal foal death, and neurological disease.
Early in April, the Pennsylvania Department of Agriculture was notified that a horse racing at Parx Racetrack in Bensalem PA had clinical signs of Equine herpes myelocencephalopathy and was being treated in isolation at a New Jersey equine veterinary hospital after having tested positive for the neuropathogenic strain of EHV-1.
That horse was later euthanized and two barns at Parx with exposed horses were placed under quarantine.
On April 10, 2016, 44 horses were released from quarantine at a Bucks County, Pennsylvania, boarding facility based on no new clinical signs of EHV-1 in any horse and negative RRT-PCR tests on whole blood and nasal swab samples for all 44, with previously positive horses testing negative twice at least a week apart.
Three clinically recovered horses remained in quarantine in an isolated area of the property.
At Parx Racetrack in Bensalem, PA, as of Wednesday afternoon (4-6-2016) there were 3 positive horses confirmed in the original exposed barn. Arrangements were underway to find isolation facilities to move the positive horses to, then start a 21 or 28 day monitoring period for clinical signs in the remaining exposed, asymptomatic horses.
A horse that was moved earlier from the original exposed barn to a second barn was suspected of having contracted the Equine Herpes virus.
At this point 2 barns are quarantined at PARX with one containing three positives. Daily monitoring of all horses in the quarantined barns is ongoing.
By April 10, 2016, four horses in the PARX EHV-1 outbreak either died or had been euthanized. These horses included the index case that was treated in isolation at a New Jersey equine clinic and two positive horses that were removed from the exposed barn to an off-site isolation barn and also another horse that developed clinical signs of Equine herpes myelocencephalopathy at PARX.
About equine herpes viruses
Equine herpes virus infection in horses can cause respiratory disease, abortion in mares, neonatal foal death, and neurological disease. The virus is not transmissible to humans. Damage to the blood vessels in the brain and spinal cord cause neurological signs to appear.
Equine herpes myelocencephalopathy is most often due to the neuropathogenic strain of EHV-1 and may occasionally be caused by the non-neuropathogenic strain of the virus.
The disease is easily spread and typically has an incubation period between 2-10 days. Respiratory shedding of the virus occurs for 7-10 days, but may last longer in infected horses.
Prevention
Horses suspected of having EHV infections should be examined by a veterinarian and tested for virus shedding. Infected horses should be isolated immediately and all contact with other horses should be avoided. Exposed horses should also be isolated.
Two main methods of prevention can be implemented to avoid EHV outbreaks. Vaccinations and biosecurity protection are both important in preventing EHV diseases and in reducing exposure.
The goal of vaccination is to induce resistance to infection prior to exposure by producing a strong and durable immune response without inducing clinical signs of the disease in the horse. Several vaccines are available for protection against both respiratory disease and abortion as a result of EHV-1 infection, but currently no equine vaccine is licensed that has a label claim for protection against the neurological strain of the virus.
Biosecurity measures include doing everything possible to reduce the chances of an infectious disease being carried onto your property by people, animals, equipment, or vehicles, either accidentally or on purpose. Anything that touches an infected horse and secretions shed by sick horses have the potential to transfer pathogens to other horses.
The immediate separation and isolation of identified suspect cases is key to disease control. Ideally, a person caring for a sick horse should not also work with or be around healthy horses. If this is impractical, it is recommended that healthy horses should be worked with first and sick horses last.