Hemorrhagic Disease in Kansas: Enzootic Stability Meets Epizootic Disease

Abstract

Kansas (USA) could represent a transition area between contrasting epidemiologic patterns of hemorrhagic disease (HD) in the midwestern United States. In this study, we compare the distribution of reported clinical HD with serologic data to determine whether the risk of HD in white-tailed deer (Odocoileus virginianus) is associated with geographic location corresponding to the reported distribution of two white-tailed deer subspecies. On the basis of a high prevalence of antibodies (91-100%) to multiple serotypes of epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV), with correspondingly few reports of clinical HD, it appears that a state of enzootic stability exists in central and western Kansas. This area corresponds to the reported range of O. virginianus texanus. In contrast, in the eastern third of the state, which corresponds to the reported range of O. virginianus macrourus, antibody prevalence is significantly lower (45%), EHDV serotypes appear to predominate, and HD, as confirmed by virus isolation, has been consistently reported. These results suggest an abrupt demarcation between enzootic stability in central and western Kansas to a pattern of epizootic HD within the eastern part of this state. Understanding host, vector, and environmental variables responsible for these contrasting patterns could have application to understanding the risk of HD in the midwestern United States.

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

“…In general, the disease is most severe in more northern latitudes, where HD occurs sporadically and where population immunity is minimal (Howerth et al 2001;Park et al 2013). In contrast, areas of enzootic stability exist in portions of the southwestern US, where high infection rates occur annually, but clinical disease is rarely reported Flacke et al 2004). In white-tailed deer, this variation in clinical response is believed to be associated with variation in both acquired (Gaydos et al 2002b) and innate immunity (Gaydos et al 2002a).…”

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

“…Epidemics are even more infrequent (historically) in more northern latitudes and in the western states and often result in high mortality Stallknecht 1992, Stallknecht et al 2002). In addition to these endemic and epidemic cycles, a pattern of endemic stability exists in WTD in certain parts of the United States where WTD are thought to co-exist with orbiviruses and their vectors , Stallknecht et al 2002, Flacke et al 2004). In these areas, prevalence of antibodies to EHDV and BTV among free-ranging WTD can approach 100% but reports of disease are extremely rare .…”

When More Transmission Equals Less Disease: Reconciling the Disconnect between Disease Hotspots and Parasite Transmission

“…A series of state-level studies of WTD populations in the US [12]–[15] suggests that there is considerable variation in transmission, with reported mean seroprevalence values in the range 8–84%. Seroprevalence determines the proportion of individuals in a population that have current or previous exposure to virus by testing for antibodies.…”