b'In 2013 Traub-Dargatz led a case control study of data from the horses at- EHV-1 Refreshertending the Ogden event.Statistically, we looked at risk factorsJosie Traub-Dargatz, DVM, MS, Dipl. ACVIM, professor emeritus at Colorado State Univer-for developing the neurologic form ofsitys College of Veterinary Medicine and Biomedical Sciences, in Fort Collins, says equine the disease among horses that attendedherpesvirus-1 (EHV-1) infection appears in horses in various ways, including:the cutting event, she says. In this and No clinical signs;other outbreaks, it appears that mares Fever;are more likely to be in the neurologic Respiratory signs, most commonly in juvenile horses younger than 2 to 3 years;cases. Mares were overrepresented, Abortion in pregnant mares, generally in late pregnancy;even when other factors were taken into Pneumonia, weakness, and other signs in young foals infected in utero; andconsideration.There have been other Neurologic disease, most often in adult horses, with rapidly developing clinical signs.outbreak investigations comparing casesIn neurologic cases, known as equine herpesvirus myeloencephalopathy (EHM), the to controls that found that mares werehorse could look normal in the morning and by the afternoon look wobbly, be leaning overrepresented. Again, we dont knowagainst a wall, or even down and unable to rise, says Traub-Dargatz. The most severe cases necessarily why that would bebut itsare ones that become recumbent and cant get up. an interesting observation. The horse might also have had a fever preceding the development of neurologic signs, Traub-Dargatz says she and her col- nasal discharge, loss of appetite, and loss of urinary bladder tone.A large percent of EHV-exposed horses dont show clinical signs but become persistently leagues determined that horses exposed infected, known as latent infection, says Traub-Dargatz.to two or more biosecurity risks (e.g., be-Its speculated with stress the virus can reactivate, Traub-Dargatz says. The body lets ing tied outside the stall or being allowedthe virus exist, because it doesnt recognize its really there in this latent form. The challenge access to a shared water source) whileis the horse can look normal, so we dont know they are shedding when this reactivation at the Ogden event were more likely tohappens. The virus persists in the population (in so-called silent shedders) through reactiva-be among the neurologic cases. I thinktion, shedding, and subsequent exposure of other horses.Natalie DeFee Mendik thats credence for taking precautions with your horses when you bring them into a situation in which they are com-mingled, she says. (PA Seeber, et al.) evaluated whetherThe Silver Lining: ImprovedThe study also showed that zinctravel and new living arrangements couldCommunicationmight play an antiherpetic role. Whencause dormant EHV-1 virus to reactivate.A reportable disease is one practitio-we compared neurologic cases to theThey examined stressors when transport- ners must report to federal, state, or local controls (horses that attended the Ogdening a captive zebra with unknown infec- health officials upon diagnosis. event and did not become sick), anothertion status to a new zoo and introducingRegulatory response to a contagious factor was that horses that were on aher to the established herd there, whichdisease begins with the veterinary practi-dietary supplement containing zinc weretioners recognition of compatible clinical at a reduced risk for being in the neuro- signs and laboratory identification of the logic cases, Traub-Dargatz says. ThereWe need to ask our- disease agent, says Katie Flynn, BVMS, is some evidence in the literature thatMRCVS, equine veterinarian for the Cali-zinc is a critical element in the immuneselves, Are there reallyfornia Department of Food and Agricul-response. Unfortunately, we didnt havemore outbreaks, or areture. Thus, a regulatory response on the enough observations to say a certain levelpart of the SAHOs requires the disease of zinc was associated with a protectivethey more visiblebe a reportable disease in a state. During effect. because there is morethe 2011 multistate EHV-1 outbreak, it EHV-1 in Other EquidsAnother out- was noted that EHV-1 was reportable in break Traub-Dargatz describes took placeconsistent reporting? only 36 states. According to a 2016 survey in Wyoming many years ago, with mul- DR. JOSIE TRAUB-DARGATZ of 49 state veterinarians in the United tiple horses infected with the neurologicStates, neurologic cases of EHV-1 were form of EHV-1. That group, however,reportable in all but one state (showing included mules, none of which displayedwere known to be latently (without show- regulatory updates), whereas cases of clinical signs. Since then, researchersing signs) infected with EHV. Research- EHV-1 respiratory disease were report-found that mules housed together withers sampled feed tubs after each meal toable in 26 states.horses in a mountain packing station inmonitor for viral shedding and measuredEHV-1 outbreak recognition is still California during an EHV-1 outbreak infecal glucocorticoid metabolites (whichevolving, says Traub-Dargatz, and might 2011 showed viral loads in blood samplesindicate increased stress levels). Theirprovide an incomplete picture: I think and nasal secretions but developed noresults showed that the stress associatedwe can have an impression that there clinical signs. Only horses showed neuro- with long-distance transport and re- are now more outbreaks, but we need logic signs (TheHorse.com/115117). structuring of social groups likely causedto be cautious of that, she says. We In a 2018 study European researchersincreased viral shedding in all animals. need to ask ourselves, Are there really TheHorse.com | The HorseAugust 201929'