Equine Health Update EHU Vol 20 Issue 03 - Page 28

EQUINE | Equine Disease Quarterly and pathologic findings, is sporadically seen in adult horses without recent administration of an equine origin biologic. These “non-biologic” cases tend to mostly occur between June and November and can occur in small outbreaks that span a few weeks. Non-biologic cases seem to occur most commonly on broodmare farms. The seasonal incidence of the non-biologic cases suggests the possibility of insect transmission of parvovirus in these “non-biologic” cases. Clinically affected horses with Theiler’s disease frequently have both neurologic signs (hepatic encephalopathy: head pressing, stumbling, blindness) and jaundice (yellow gums and eyes). Once the neurologic signs are noted, there is a rapid progression to death in approximately 70 percent of the cases. Horses that receive supportive therapy and survive for five days after the onset of fulminant disease generally recover and have no long-term effects. Another recently discovered virus that causes liver disease in horses is non-primate hepacivirus (NPHV). NPHV is genetically the closest homolog of human hepatitis C virus (HCV) discovered to date. Experimental horse infections consistently result in biochemical and histopathologic evidence of hepatitis, but the disease is mild and clinical signs are either absent or very mild in recently infected horses. NPHV and equine parvovirus are present in some healthy horses, indicating that horses can become healthy carriers of these viruses. The USDA Center for Veterinary Biologics has issued a notice that all licensed equine blood products have to test free of equine parvovirus and NPHV. This should improve horse health by eliminating most of the blood product-associated cases of hepatitis. Non-biologic associated cases will likely continue to occur until natural means of virus transmission are determined 28 and necessary control methods implemented. CONTACT: Thomas J. Divers, Joy E. Tomlinson and Gerlinde R. Van de Walle, tjd1@cornell.edu, (607) 253-3100, College of Veterinary Medicine, Cornell University, Ithaca, NY Importance of Protecting your Horse against Eastern Equine Encephalomyelitis and West Nile Encephalitis The two most frequently encountered causes of equine encephalitis or equine encephalomyelitis in North America are Eastern Equine Encephalomyelitis (EEE) and West Nile Encephalitis (WNE) viruses. Both are mosquito-borne and neurotropic. The respective viruses are not restricted to equids in terms of their host range; each can be transmitted to humans and certain other mammalian and avian species. Both diseases are a source of concern for the equine industry not only from the potentially life-threatening consequences of either infection, but also from the economic losses involved. Eastern equine encephalomyelitis poses an annual threat to equids in the Gulf and Atlantic coastal states and the Great Lakes region, extending in certain years as far north as eastern Canada. It is occasionally recorded in some inland states such as Arkansas, Oklahoma, Tennessee, Kentucky, and Iowa. Evidence of EEE activity is most often reported in Florida, in which it has been confirmed as early as January, as recorded in 2018. Over the past 15 years, the yearly incidence of EEE cases in equids has ranged from 60 (2011) to 712 (2003), with an annual average of 206 cases. In 2017, 86 cases of the disease were reported in 13 states. In temperate regions, transmission of EEE virus is • Equine Health Update •