Epizootiology of an Epizootic Hemorrhagic Disease Outbreak in West Virginia

Abstract

An outbreak of epizootic hemorrhagic disease virus, serotype 2 (EHDV-2) was responsible for localized white-tailed deer (Odocoileus virginianus) mortality in Hardy and Hampshire counties, West Virginia (USA), in the summer and fall of 1993. Using available historical data on regional herd immunity, data opportunistically collected during the epizootic, and postepizootic sampling of hunter-harvested deer, we grossly estimate certain epidemiologic parameters and compare findings to a hypothesis about hemorrhagic disease outbreaks in the Appalachian Mountains. During the epizootic, 57.9 km(2) were actively searched and 228 dead deer were found. Epizootic hemorrhagic disease virus, serotype 2 was isolated from seven of nine deer sampled in Hardy and Hampshire counties. Preepizootic exposure of deer to EHD viruses was unknown, but available data suggest that it was negligible. The geographic distribution of the outbreak was defined by plotting the locations of dead deer found during the outbreak, as well as the locations of deer harvested by hunters after the outbreak that had antibodies to EHDV-2 on a map sectioned into 16.65 km(2) rectangular sections. Sections that included one or more dead deer or hunter-harvested deer with antibodies to EHDV-2 were included in the defined outbreak area. Postoutbreak sampling revealed monospecific EHDV-2 antibodies in 12% of deer harvested by hunters within the defined outbreak area. Based on the available data and accepting certain assumptions, gross calculations suggest that this outbreak appears to have been isolated and probably killed a high percentage of the deer that were infected. This is consistent with the hypothesis that sporadic hemorrhagic disease outbreaks in the Appalachian Mountains are usually localized and severe.

Apparent Increase of Reported Hemorrhagic Disease in the Midwestern and Northeastern Usa

“…Furthermore, although the changing patterns we describe were measured over 33 yr, there is no basis to determine if they will persist. However, based on limited field and experimental data, incursions of these viruses into naïve white-tailed deer populations can result in estimated population losses of 6-16% (Missouri; Fischer et al 1995) and 20% (West Virginia; Gaydos et al 2004). If such outbreaks occur more commonly on a 2-to 3-yr cycle, as reported for Virginia and the southeastern US (Howerth et al 2001;Sleeman et al 2009) and if changing climate conditions result in more numerous largescale regional outbreaks as observed in 2007 and 2012, potential population impacts or management implications related to increased nonhunting mortality are possible.…”

Transmission and Epidemiology of Bluetongue and Epizootic Hemorrhagic Disease in North America: Current Perspectives, Research Gaps, and Future Directions

“…Given the growth of freeranging WTD populations over the past 60 years in the face of cyclical EHD outbreaks, there are no indications that EHD will limit long-term population growth (Stallknecht et al 2002). However, the potential for negative impact on wild ruminant populations is understudied (Fischer et al 1995, Beringer et al 2000, Gaydos et al 2004, and given the dynamic pressures on wild populations in a changing environment, the possibility should not be dismissed.…”

Epizootic haemorrhagic disease

“…In white-tailed deer, the disease is characterised by fever, weakness, inappetance, excessive salivation, facial oedema, hyperaemia of the conjunctiva and the mucous membranes of the oral cavity, coronitis, and stomatitis (1,5,7,9,12). Fulminant EHD is characterised by excessive bleeding (haemorrhagic diathesis), dehydration, diarrhoea, and death.…”

“…Although recognised earlier in the south-eastern United States, EHD was first described after a severe outbreak of the disease in white-tailed deer in New Jersey in 1955 (5). Epidemics of EHD continue to occur regularly in this species throughout much of North America east of the Rocky Mountains (1,2,6,7,8,9,10,11,12,13). The disease also occurs sporadically in American pronghorn antelope and bighorn sheep, and was documented recently in brocket deer in Brazil and captive yaks in Colorado (1,2,13,14).…”