Files
Abstract
In recent years, numerous arboviruses have emerged or re-emerged as significant human and domestic animal pathogens. In an effort to better understand viral ecology and predict risk to specific human and livestock populations, surveillance of wildlife has proven to be a valuable tool. The current work focuses on the utility of surveillance of white-tailed deer (Odocoileus virginianus) for the detection of selected arboviruses of current concern to US wildlife health, human health, and domestic ruminant production, namely Heartland virus (HRTV) and bluetongue virus serotype 3 (BTV-3). The following thesis reviews the existing literature describing known arboviruses that can infect and, in some cases, cause disease in white-tailed deer. The potential use of WTD as a sentinel species for these viruses is also reviewed. Three experimental chapters are described, including the experimental infections of white-tailed deer fawns with HRTV and BTV-3, as well as a retrospective serosurvey spanning 15 years to detect HRTV-neutralizing antibodies in sera from free-ranging white-tailed deer. Experimental inoculation of deer did not result in a detectable viremia in inoculated deer, but fawns did seroconvert. These results suggest that while white-tailed deer may not be a competent host for HRTV, they may still act as an indicator of virus circulation in regional tick populations. This is supported by the results of the serosurvey, which indicate that HRTV-neutralizing antibody-positive deer have been present in the Southeastern US as much as 8 years previous to the identification of HRTV infection in a human, and that the detection of antibodies in deer is associated with the presence of suspected tick vectors in that location. Fawns infected with BTV-3 experienced a viremia similar to previous infections of deer with other BTV serotypes, peaking at 105-107 TCID50/mL of blood on post-inoculation day 5. Clinical disease was mild, and there was no seroconversion or sequential drop in viremia in the two fawns that survived to post-inoculation day 12, and there was a lack of IFN response seen in previous studies, indicating that responses to BTV infections may vary with the age and immunity of deer when infected. Overall, results of these studies support the use of white-tailed deer as advantageous sentinels for some arboviruses and arboviral diseases and, therefore, indicate that continued monitoring of deer in endemic and neighboring regions is warranted.