Equid Herpesvirus‐Associated Myeloencephalopathy

New Insights into the Management of an EHV-1 (Equine Hospital) Outbreak

“…When to lift quarantine restrictions from premises can be a challenging decision, as there are multiple criteria presented by various experts to take into consideration, and no one protocol is 100% secure with regard to further spread of the disease. In the event of a neurological outbreak of EHV-1, it is important to consider all in-contact horses involved to be infectious until at least 21 days after the onset of clinical signs [ 6 ]. The recent AAEP guidelines extended this to 28 days because of evidence of more protracted shedding in some clinical cases of EHM [ 17 ].…”

“…The recent AAEP guidelines extended this to 28 days because of evidence of more protracted shedding in some clinical cases of EHM [ 17 ]. The use of diagnostic testing to determine the status of viral shedding is the most pragmatic approach [ 18 ], with PCR testing beginning 14 days after the last day of recorded fever [ 6 ]. WEH used this approach, although the discharged horses only tested negative on nasopharyngeal swabs taken at least 21 days after the last day of recorded fever, with the expectation that horses were no longer shedding once testing negative.…”

“…The safety concerns when performing a spinal tap procedure on an ataxic horse with a risk of reaction during the procedure make it more difficult. Despite these limitations, this test can be supportive in confirming a diagnosis while qPCR results are pending [ 2 , 6 ].…”

“…It is widely believed that there has been a recent increase in the prevalence of EHV-1 outbreaks [ 6 ]. During an outbreak, the majority of a herd will develop a primary infection with 10–40% going on to develop EHM.…”

“…EHV-1 is usually transmitted by direct (nose-to-nose) contact, through aerosols, which may have played a significant role during the high case fatality rate in the Valencia 2021 outbreak. Furthermore, in abortion cases caused by EHV-1, virus can be found in fetal fluids and membranes as a result of high viremic loads [ 6 ]. Horses with signs of EHM also likely still shed the virus via the respiratory tract.…”