Surveillance for Serological Evidence of Bourbon and Heartland Virus Infection in White-Tailed Deer and Feral Swine in Texas

Background: The tick-borne pathogens, Bourbon virus (BRBV) and Heartland virus (HRTV) are the cause of febrile illnesses that may progress to severe and fatal diseases. Materials and Methods: As a preliminary effort to determine if these viruses were enzootic in Texas, ticks and blood samples were collected from feral swine (Sus scrofa) and white-tailed deer (Odocoileus virginianus) (WTD) killed by gunning as part of an abatement program during 2019-2021 in Travis County, Texas. Ticks were collected from these animals by hand and blood samples were obtained by cardiac puncture using 22-gauge needles and 5 mL syringes. Information was recorded for each animal, including date, sex, and location. The species of ticks were identified morphologically using a taxonomic key, and serum samples were tested for neutralizing antibodies to BRBV and HRTV. Results: A total of 83 Ixodes scapularis and 58 Amblyomma americanum ticks were collected from feral swine, and 196 I. scapularis and 11 Dermacentor albipictus from WTD. Although A. americanum, the implicated vector of both viruses was collected from feral swine, neutralizing antibody was not detected to BRBV, but 12% (9/75) had antibody to HRTV as evidence of a previous infection. Of the serum samples obtained from WTD, all were negative for BRBV neutralizing antibody, but 6.6%% (5/75) were positive for HRTV antibody. Conclusion: These preliminary results indicated that HRTV was enzootic in Travis, County, Texas and further studies are warranted to determine the specific tick vectors and the possible role of WTD and feral swine in the maintenance and transmission cycle of this virus.