Zoonotic Potential (Rocky Mountain Spotted Fever and Tularemia) in the Tennessee Valley Region

Abstract
A survey was conducted from July 1969 through January 1972 in Land Between the Lakes, an outdoor recreation and conservation education area in the Tennessee Valley Region, to determine the occurrence of Rickettsia rickettsi and Francisella tularensis, the agents of spotted fever and tularemia, respectively, in wild mammals and their ticks. Serologic evidence suggested that both pathogens are widely distributed among a large variety of medium-sized mammals throughout the area. Fifty-five of 666 sera comprising 8 of 22 animal species had complement-fixing antibodies to spotted fever antigens, with cottontail rabbits (32 of 66), raccoons (8 of 163), and woodchucks (6 of 49) giving the largest number of seropositives. Antibodies to tularemia were detected in 117 of 620 sera with highest prevalence among striped skunks (11 of 16), gray foxes (37 of 72), raccoons (73 of 161), and woodchucks (17 of 48). Dermacentor variabilis was the only species of tick from which R. rickettsi and F. tularensis were isolated. Of 931 adults collected off host animals or by dragging, 51 were infected with spotted fever rickettsiae; 39 of these yielded strains pathogenic for laboratory animals. Seven ticks, two of them also infected with R. rickettsi, contained F. tularensis. An unidentified bacterium-like microorganism was detected by hemolymph examination in 80 D. variabilis. This organism appeared unrelated to rickettsiae and proved nonpathogenic for meadow voles. A rickettsia-like organism antigenically related to the spotted fever group was noted in 64 of 545 Amblyomma americanum; it, too, failed to produce detectable infection or antibodies to spotted fever group antigens in meadow voles.

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