Tick-Host Interactions between White-Tailed Deer (Odocoileus virginianus) and Two Tick Species of Medical and Veterinary Importance

Abstract

White-tailed deer (Odocoileus virginianus Zimmerman) are a main host for blacklegged (Ixodes scapularis Say) and Lone Star ticks (Amblyomma americanum Linnaeus), which transmit nearly half of human tick-borne disease agents including the Lyme disease agent. The population increase of white-tailed deer in the twentieth century has correlated with the rise of various tick-borne pathogens that are known to be spread by blacklegged, Lone Star, and other species of ticks. To determine tick feeding and reproductive parameters when fed on white-tailed deer, we experimentally infested eight white-tailed deer (N = 8) with blacklegged ticks (N = 50 adult tick pairs per deer), and three white-tailed deer (N=3) with Lone Star ticks (N = 50 adult tick pairs per deer). Determining an effective immunization dosage of a tick salivary antigen-based vaccine that will only need to be administered to the host one-time has vital implications. We tested a candidate antigen cocktail containing tick-salivary proteins that were proven effective in rabbits. Deer were inoculated with two dosages of the antigen cocktail (low dose N = 4, high dose N= 4), and an adjuvant-only group was included for comparison (control/adjuvant N = 4). All deer were infested with ticks (N = 50 mated tick pairs per deer) for a total of three cycles post-inoculation to determine the effects of the candidate antigens on tick feeding and reproductive parameters. Deer in the vaccine groups developed antibodies to some, but not all, of the antigens in the cocktail indicating these antigens were immunogenic. However, there was no apparent effect of this specific cocktail on time to repletion, replete female weight, weight of egg mass, or larval hatch percentage.