07/10/2023
Hi everyone,
In case you haven't heard, there has been one positive case of EHV-1 at Thunderbird last week. Paton and Martin Vet Services received one PCR positive test back late Friday evening, for a horse that did not have a fever and was showing mild respiratory signs earlier in the week. The test was positive for EHV-1 non-neuropathic strain. A second horse with mild symptoms from the same stable tested negative. All horses from that stable were removed from the showgrounds as a precaution, all were clinically normal. Dr. Paton does not know of any other positives or horses showing respiratory signs and believes this to currently be a low-risk situation, though biosecurity precautions are still warranted.
Equine Herpes Virus (Rhinopneumonitis)
EHV-1 and EHV-4 are the most common strains of equine herpes circulating in the equine population. Both strains are one of the most prevalent causes of mild respiratory symptoms in horses. Most horses have been exposed to EHV by the age of two. EHV-1 is most commonly an upper respiratory infection where horses exhibit ocular and nasal discharge, but not a cough, often have a biphasic fever (horses have a fever on Day 1 of clinical signs and Day 6-7). If clinical disease occurs, it usually becomes apparent by Day 4-6 after infection, though a 24hr incubation can occur. Once a horse shows signs, it is usually self-limiting within 7 days, though supportive care (such as anti-inflammatories for horses with a fever) and isolation from other horses is warranted. EHV is transmitted by direct contact, by shared airspace and via fomites (human hands, gear, buckets, etc.). The virus can survive in the environment for up to 7 days.
EHV-1 can be a neuropathic disease, though this is far more rare. Neurologic signs generally occur 24-48 hrs after infection. Treatment for the neurologic form is also supportive, however this form can be fatal. EHV can also cause abortions and more severe respiratory disease in foals.
Control:
We would recommend that if any horses at Tbird or returning from Tbird are showing respiratory symptoms, including nasal discharge, even if they don't have a fever, they should be tested for EHV via PCR, which can be done with a nasal swab or blood. Any horses showing respiratory symptoms should be isolated from other horses, this includes no sharing of airspace, tack, feed buckets, etc.. Even without any horses showing respiratory symptoms, all horses' temperatures should be checked twice daily and should be below 38.3C. Strict hygiene should be adhered to when moving between horses I.e. handwashing and hand sanitizer, avoidance or disinfection of all shared tack, gear, buckets etc..
When returning from Tbird, isolate all horses that attended the show from the rest of your herd for 7 days, if possible, and continue all strict hygiene protocols and disinfection of gear between horses for 7 days after that. Boot dips containing a harsher disinfectant, such as bleach, should be at all exits from areas where potentially exposed horses are kept.
Please contact our office if you have any further questions or if your horse has respiratory symptoms or fever and has either been to Thunderbird recently or potentially exposed to a horse recently at Tbird.
