Rocky Mountain spotted fever (RMSF) is the most common tick-borne illness in Tennessee. Little is known about the occurrence of R. rickettsii, the causative agent, in ticks in Tennessee. To better understand the prevalence and distribution of rickettsial agents in ticks, we tested 1,265 Amblyomma, Dermacentor, and Ixodes adult and nymphal ticks. Additionally, we tested 231 Amblyomma americanum larvae. Ticks were collected from 49 counties from humans, wild animals, domestic canines, and flannel drags. Spotted fever group rickettsiae (SFGR) DNA was detected by polymerase chain reaction (PCR) in 32% of adult and nymphal ticks. A total minimum infection rate of 85.63 was found in larval pools tested. Three rickettsial species, Rickettsia montana, Rickettsia amblyommii, and Rickettsia cooleyi were identified by molecular analysis. Rickettsia rickettsii was not detected. This study suggests that some RMSF cases reported in Tennessee may be caused by cross-reactivity with other SFGR antigenically related to R. rickettsii.

Abstract. Rocky Mountain spotted fever, Lyme disease, and ehrlichiosis are tick-borne diseases that are reported annually in Kentucky. We conducted a survey to describe infection prevalence of tick-borne pathogens in Amblyomma americanum and Dermacentor variabilis ticks collected in Kentucky. During 2007-2008, we collected 287 ticks (179 D. variabilis and 108 A. americanum ) from canine, feral hog, horse, raccoon, white-tailed deer, and human hosts in six counties in Kentucky. Ticks were screened for Rickettsia spp., Borrelia spp., and Ehrlichia spp. by using polymerase chain reaction. Forty-one (14.3%) ticks (31 A. americanum and 10 D. variabilis ) were polymerase chain reaction-positive for a Rickettsia spp. Fourteen (4.9%) ticks (6 A. americanum and 8 D. variabilis ) were positive for E. chaffeensis , and 4 A. americanum (1.4%) were positive for E. ewingii . One (0.4%) A. americanum was positive for Borrelia lonestari .

Human ehrlichiosis is the second most common tick-borne disease reported in Tennessee after Rocky Mountain spotted fever. Two closely related ehrlichiae, Ehrlichia chaffeensis and Ehrlichia ewingii, are both causative agents of human disease and are transmitted by Amblyomma americanum, the lone star tick. Prevalence rates and distribution patterns of these pathogens among ticks in Tennessee are currently unknown. To understand prevalence and exposure risk of Ehrlichia spp., we tested 616 ticks (309 Amblyomma americanum (L.), 277 Dermacentor variabilis (Say), 17 Ixodes texanus (Banks), 7 Ixodes cookei Packard, 4 Ixodes scapularis (Say), and 2 Amblyomma maculatum Koch) from 46 counties for E. chaffeensis and 324 ticks (238 A. americanum and 86 D. variabilis) from 29 counties for E. ewingii. Overall, E. chaffeensis was detected in 2.6% (8/309) of A. americanum and E. ewingii in 0.8% (2/238). Ehrlichia spp. DNA was not detected in any tick species other than A. americanum. Although sample sizes were low in many counties, all positive ticks were identified in the Interior Plateau and Southeastern Plains ecoregions which is where the majority of human ehrlichiosis cases are reported from Tennessee (e.g., 66.3% of the human cases in 2008 are from the Interior Plateau ecoregion). The data from this pathogen survey combined with frequent human case reports from certain areas indicate potential "hot spots" for ehrlichiosis infection. Targeted vector control interventions in these areas may help decrease human ehrlichiosis transmission.

Trypanosoma cruzi , the etiologic agent of Chagas' disease, is enzootic in animal populations of the southeastern United States. In the United States, T. cruzi prevalence has been reported for over 20 different wildlife species, and 7 autochthonous human cases have been documented since 1955. Previous canine (Canis familiaris) serosurveys have been limited either by small sample size or confined geographic reporting areas. In this study, we report a seroprevalence of 6.4% among 860 canines from 31 counties and 5 ecoregions throughout Tennessee, using an indirect immunofluorescent assay (IFA). Statistically significant associations between seropositivity and age, weight, and outdoor living were noted. Differences in seropositivity were not seen based on American Kennel Club (AKC) group, sex, habitat, land cover, and ecoregion. Greater attention should be given to possible T. cruzi transmission in Tennessee and veterinarians should consider Chagas' disease as a differential diagnosis with compatible signs.

Trypanosoma cruzi is the etiologic agent of Chagas' disease. Autochthonous human and canine transmission of T. cruzi has been documented in Tennessee, but little is known about its ecology, including the prevalence of T. cruzi among wildlife in Tennessee. Serum samples from 706 raccoons (Procyon lotor) from 10 counties in the Ridge and Valley and Blue Ridge Mountains ecoregions of eastern Tennessee were tested for antibodies reactive with T. cruzi using the indirect fluorescent antibody assay. Two hundred six (29.2%) samples were seropositive, with 9 counties yielding positive samples (range 14.6-63.6%). Significantly more raccoons from rural habitats (35.1%) were found positive for T. cruzi exposure than were those from suburban habitats (23.1%, P < 0.001). Land cover class was not associated with seropositivity status (P = 0.441), even though deciduous forest was the most common site from where raccoons were trapped and the most common site of positive raccoons in rural areas (42%). Interestingly, age was positively associated with seropositivity. Raccoons older than 1 yr (adults) were 40.1% seropositive compared to 12.2% of those less than 1 yr (juveniles; P < 0.001). Female adults were significantly more likely to be exposed to T. cruzi than were male adult raccoons (P < 0.001). No significant seroprevalence difference was seen among male and female juveniles. This study contributes to understanding the dynamics of T. cruzi exposure within raccoon populations in Tennessee. The importance of habitat (rural vs. suburban) and microhabitat (dens) in risk of exposure to these populations is also discussed.