Tick control and tick transmitted disease monitoring in Eastern Tennessee

A tick control program targeted at free-living lone star ticks (LST) on white-tailed deer within the community of Fairfield Glade, TN, evolved from an investigation of an outbreak of human ehrlichiosis in that area in 1993. Ivermectin-impregnated corn was fed to deer in an effort to reduce both the reproductive capacity of the lone star ticks and the numbers of free-living individuals from 1994 to 1996. Treated corn was fed to the deer from mid-spring until July 31, 1994 to 1995 and until August 31 in 1996. Free-living tick stages were sampled in three separate sites in both the untreated and treated areas. One square meter flannel drags were used to sample for adults, nymphs and larval masses. One meter square CO2 traps were used to sample for questing life stages of the adults and the nymphs. Reductions were observed among all life stages of LST between 1994 and 1996 in the treated area which is in contrast to the untreated, control area where significant differences were observed among some years, but yearly fluctuations ruled out any pattern. Regression analysis of the number of lone star tick larval masses being produced by female lone star ticks showed ca. 10 times fewer larval masses produced on a per female basis in the treatment area. Canine populations were evaluated as an indicator species for predicting outbreaks of tick transmitted diseases in human populations. Blood was collected from 53 owner dogs in two communities in Cumberland County and from 104 shelter dogs in Cumberland (n=33) and Knox (n=71) Counties in the spring and fall of 1996 for a series of serological tests to establish exposure to the disease organisms causing canine ehrlichiosis (CE), Rocky Mountain spotted fever (RMSF) and Lyme disease. Evidence of exposure to all three diseases was found in Knox County, whereas exposure to only Lyme disease and RMSF was documented in Cumberland County. Overall, 4, 18, and 14% of dogs tested were positive to the disease organisms causing CE, RMSF, and Lyme disease. Data on canine risk factors were obtained from owner questionnaires and tick collections at owner residences. Initial findings are inconclusive, and additional sampling is necessary to determine the efficacy of using canine populations as a sentinel species for predicting outbreaks of tick-borne diseases