Coyotes exhibit immune and genetic evidence of rickettsial infections in Arizona

Green, Eric Nathaniel (2018) Coyotes exhibit immune and genetic evidence of rickettsial infections in Arizona. Masters thesis, Northern Arizona University.

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Abstract

Rocky Mountain Spotted Fever (RMSF), caused by the bacterium Rickettsia rickettsii, was recognized as endemic in Arizona after a 2004 outbreak, and has been a public health concern since that time. The brown dog tick (Rhipicephalus sanguineus) is the primary vector in the state. Since it selects domesticated dogs as the primary host, free-roaming dogs in peridomestic areas have been named as the primary risk factor for human cases of RMSF. However, the sudden emergence and long-distance transmission of the pathogen have not been adequately explained, and one possible mechanism could include a wildlife component. Since coyotes are prevalent in Arizona, wide-ranging, and genetically-similar to dogs, we predicted that brown dog ticks might parasitize coyotes and that coyotes would therefore have evidence of pathogen exposure. We tested coyote sera for antibodies to R. rickettsii. Eight out of 94 (8.5%) samples were seropositive at 1:256 or higher titers. Subsequent qPCR analyses of coyote skin showed evidence for Spotted Fever Group Rickettsia in 4 out of 138 (2.9%) samples, but not for R. rickettsii. Antibodies are cross-reactive for many rickettsiae, so the positive results in serology could indicate coyotes’ exposure to diverse, nontypical rickettsial species with various levels of pathogenicity. This cross-reactivity may play a role in the maintenance of rickettsial bacteria in Arizona. Although the specific mechanisms remain unknown, it is possible that Rh. sanguineus are responsible for transferring rickettsial pathogens across canine host species. Alternatively, a different pathogen-vector complex could be operating on coyotes than on dogs.

Item Type:	Thesis (Masters)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	Brown dog ticks (Rhipicephalus sanguineus); Coyotes (Canis latrans); Disease ecology; Rocky Mountain spotted fever (Rickettsia rickettsii); Vector-borne disease; Veterinary medicine
Subjects:	Q Science > QL Zoology
MeSH Subjects:	C Diseases > C01 Bacterial Infections and Mycoses
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > Biological Sciences
Date Deposited:	04 May 2021 19:19
URI:	http://openknowledge.nau.edu/id/eprint/5433

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