Equine Health Update EHU Vol 20 Issue 03 - Page 29

Equine Disease Quarterly | EQUINE seasonal, occurring in the summer and the fall. In sub- tropical regions such as Florida, there is a year-round risk of EEE, with virus transmission peaking in the summer months. Equids and humans are tangential or dead-end hosts of EEE virus and neither plays a role in the natural life-cycle of the virus. Infections in horses, mules, and donkeys are frequently life-threatening; case fatality rates can be as high as 90 percent. West Nile encephalitis (WNE) is also a cause of significant concern to veterinary practitioners and members of the equine industry. Within four years following initial introduction of the causal virus in New York State in 1999, the virus had spread to 48 states and several provinces in Canada. Since 1999, the yearly incidence of WNE cases in equids has ranged from 60 (2000) to 15,257 (2002). The annual average number of cases over the past 10 years was 272. In 2017, 307 equine cases were reported in 39 states. Similar to EEE, transmission of WNE virus is seasonal, occurring in the summer and extending well into the fall. Neither equids nor humans serve as amplifying hosts for WNE virus insofar as viremias are insufficient in magnitude and duration to infect mosquitoes. Unlike EEE, only about 10% of WNE virus-exposed horses will develop clinical infections. Reported case-fatality rates in affected horses can reach 30-40 percent, less than half that encountered in cases of EEE. The American Association of Equine Practitioners (AAEP), in accordance with criteria defined by the American Veterinary Medical Association with respect to “core vaccines”–namely those that protect against diseases that are endemic, of potential public health significance, and represent a risk of causing severe disease—strongly recommends that horses be immunized against EEE and WNE. Available inactivated whole-virus vaccines against EEE (including Western Equine Encephalomyelitis) have been shown to be safe and effective in protecting against this disease. Two inactivated whole-virus vaccines, a live canary pox vector vaccine and an inactivated flavivirus chimera vaccine are available against WNE. All have been confirmed safe and effective in preventing the disease. Despite the AAEP recommendations to horse owners to vaccinate their horses against EEE and WNE, regrettably many fail to do so. The vast majority of equine cases of EEE and WNE either have no history of vaccination against the particular virus or else the vaccination history is incomplete. There is need for an ongoing concerted effort, utilizing all avenues of communication including social media, to alert horse owners of the dangers of these two vector-borne diseases and of the importance of vaccination as an effective means of prevention and averting the losses that continue to occur every year in unprotected horses. CONTACT: Peter J. Timoney, MVB, MS, PhD, FRCVS, ptimoney@ uky.edu, (859) 218-1094, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, KY Rabies in the Horse and Beyond in Kentucky: A Look at the Last 29 Years Rabies virus exposure typically occurs following the bite of an infected animal. Depending on the anatomic site of exposure, an incubation period of variable duration follows as the virus evades the immune response by hiding in the central nervous system. Amplification of the virus occurs in the dorsal root ganglion after which it travels towards the brain via the spinal cord. At this point, clinical signs • Volume 20 Issue 3 | October 2018 • 29