Submitted to: Vector-Borne and Zoonotic Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2008
Publication Date: 8/4/2009
Citation: Gatewood, A.G., Rollend, L., Papero, M., Carroll, J.F., Daniels, T., Mather, T.N., Schulze, T.L., Stafford, K.C., Fish, D. 2009. Effects of tick control by acaricide self-treatement of white-tailed deer on host-seeking tick infection prevalence and entomologic risk for Ixodes scapularis-borne pathogens. Vector-Borne and Zoonotic Diseases. 9:431-437. Interpretive Summary: Blacklegged ticks (deer ticks) are the principal vectors of the pathogen causing Lyme disease and also transmit human granulocytic anaplasmosis (ehrlichiosis). Most cases of Lyme disease in humans are due to being bitten by infected blacklegged tick nymphs. The efficacy of ‘4-poster’ deer self-treatment devices, developed by researchers at the USDA, ARS Knipling-Bushland U. S. Livestock Insects Research Laboratory , Kerrville, TX, was tested in field trials at locations in five states. Host-seeking blacklegged ticks collected from treatment and control sites annually were tested for the presence of Borrelia burgdorferi, the pathogen causing Lyme disease. Populations of blacklegged ticks were reduced at ‘4-poster’ sites during the USDA Northeast Tick Control Project (1998-2002). The density of nymphs infected with the Lyme disease pathogen was reduced 68% compared to untreated control areas, as was the entomologic risk of Lyme disease. These findings are of interest to researcher, public health officials and the general public living or working in areas where Lyme disease is prevalent. The ‘4-poster’ technology is now commercially available.
Technical Abstract: We evaluated the effects of tick control by acaricide self-treatment of white-tailed deer on the infection prevalence and entomologic risk for three I. scapularis-borne bacteria in host-seeking ticks. Ticks were collected from vegetation in areas treated with the ‘4-Poster’ device and from control areas in 5 geographically diverse study locations in the Northeastern US and tested for infection with two known agents of human disease, Borrelia burgdorferi and Anaplasma phagocytophilum, and for a novel relapsing fever-group spirochete related to B. miyamotoi. Approximately 2,000 adults and 4,000 nymphs were assayed over the 6-year project period. Overall, 38.2% of adults and 12.5% of nymphs were infected with B. burgdorferi; 8.5% of adults and 4.2% of nymphs were infected with A. phagocytophilum; and 1.9% of adults and 0.8% of nymphs were infected with B. miyamotoi. In most cases, treatment with the 4-Poster device was not associated with changes in the prevalence of infection with any of these three microorganisms among nymphal or adult ticks. However, the density of nymphs infected with B. burgdorferi, and consequently the entomologic risk for Lyme disease, was reduced overall by 68% in treated areas compared to control areas among the 5 study sites at the end of the study. The frequency of bacterial co-infections in ticks was generally equal to the product of the proportion of ticks infected with a single bacterium, indicating that enzootic maintenance of these pathogens is independent. Controlling ticks on deer by self-application of acaricide results in an overall decrease in the human risk for exposure to these three bacterial agents that is due solely to a reduction in tick density.