Authorities in several US states are undertaking tracing after probable cases of the neurological form of equine herpes virus-1 that appear to be linked back to a Tennessee trail ride late last month.
The illness has reportedly affected horses in Tennessee, Mississippi and Kentucky.
The Tennessee Department of Agriculture said six to eight suspected cases of the neurological form had been reported to the state veterinarian’s office in horses that participated in the Bucksnort Trail Ride, held from April 23–30, in Humphreys County.
The event drew about 100 horses from multiple states. The movement of horses that attended the event is being restricted on a case by case basis, the department said.
To date, it is understood four horses have died from the contagious viral disease.
State animal health officials are working with event organizers, neighboring state veterinarians and private veterinarians to identify other horses that may have been exposed or are exhibiting symptoms.
Tennessee state veterinarian Charles Hatcher has recommended that horse owners who participated in the Bucksnort event work with their veterinarian to restrict movement and to monitor their horses.
Hatcher also recommended that isolation and monitoring continue for 28 days if any clinical signs of disease were observed.
Equine herpes virus is highly contagious among horses but poses no threat to humans. The symptoms of the neurological form in horses may include a fever, nasal discharge, wobbly gait, hind-end weakness, dribbling of urine and diminished tail tone.
The virus is easily spread by airborne transmission, horse-to-horse contact and by contact with nasal secretions on equipment, tack, feed and other surfaces. Horse owners can spread the virus to horses if their hands, clothing, shoes or vehicles are contaminated. The virus can cause aborted foals and can be fatal in some cases.
Rusty Ford, equine programs manager for the Office of State Veterinarian in Kentucky, said late on Wednesday afternoon the Tennessee Department of Agriculture alerted Kentucky authorities about the outbreak.
Information provided by Tennessee officials describe horses as presenting with varying symptoms that include neurological abnormalities.
The illness has resulted in four horse deaths, with four additional horses showing similar symptoms, Ford said.
Organisers of the trail ride provided Tennessee officials with a list of participants that included seven Kentucky residents.
These individuals participated with eight horses originating from the Kentucky counties of Edmonson, Logan, Simpson, Todd and Warren.
One of these horses is included as a fatality of the illness, Ford said.
Veterinarians and the owners of the remaining seven horses all report the horses returned from the trail ride in good form and remain bright, alert, responsive and healthy this morning.
These seven horses are not known to have direct contact with any sick animal and will continue to be monitored closely.
Diagnostic samples collected from the single Kentucky fatality have been submitted for diagnostic testing.
Other horses on the same farm are under veterinary restriction pending a determination as to what caused the horse’s illness.
Preliminary testing has detected EHV-1 viral DNA in at least two of these cases. Additional and more definitive testing continues.
Ford said results of the investigation to date show that, at this time, Kentucky’s equine population was minimally impacted.
That said, he encouraged elevated biosecurity precautions be implemented by Kentucky facility managers and managers of shows/exhibitions/trail rides in the state.
“We have been contacted by and provided guidance to trail-ride managers on precautionary measures that should be implemented stressing that the goal of a biosecurity plan is to prevent the transmission of infectious agents among individuals.”
The State Veterinarian’s Office in Mississippi said it was notified on May 9 of two confirmed cases of EHV. In addition, four other cases of suspected EHV-1 have also been reported. To date, three of these horses have died or been euthanized and three were ill with neurological disease.
The ill horses in Mississippi had been isolated and were being treated by their attending veterinarian.
All Mississippi Bucksnort Trail Ride participants are being notified about the situation and the necessity for isolation and monitoring horses taken to the event.
“The potential for exposure to other horses is also being evaluated,” the office said. “At this time, there has been no spread to other horses in Mississippi.”