Abstract

Twenty adult desert bighorn sheep (Ovis canadensis mexicana) were sampled from a population in the Mazatzal Mountains of central Arizona during multiple captures between June 2000 and October 2002. Serologic, nasal, pharyngeal, and cervical swab, fecal, and ectoparasite samples were examined for evidence of pathogen exposures during drought conditions prior to and following removal and exclusion of domestic livestock from the study area. Evidence of bacterial and viral activity persisted throughout the study, and was unremarkable in comparison to seroprevalence and antibody titers against disease agents reported for other desert bighorn populations. Results indicated lower than normal rainfall and removal of domestic livestock had no influence on exposure to leptospiral or viral diseases, and disease was not a factor limiting bighorn population growth and production. However, seroprevalence of antibodies against Chlamydia sp. increased during a year of exceptionally low rainfall, and incidence of pneumophilic bacteria in nasal swabs declined after livestock removal. We suggest our findings are consistent with enzootic stability and levels of immunity corresponding with absence of clinical disease in the Mazatzal Mountains desert bighorn sheep population. Continued monitoring of disease exposure and population trends in relation to variables such as presence or absence of domestic livestock, densities of bighorn and sympatric ungulates, rainfall levels, and translocations are key to understanding effects and etiology of desert bighorn sheep diseases.

Acknowledgments

Federal Aid in Wildlife Restoration Project W-78-R of Arizona Game and Fish Department and the Arizona Desert Bighorn Sheep Society provided financial support. We thank T. Smith, D. Conrad, L. Phoenix, B. Anthony, and J. Hanna for assistance in capture and sampling.