Seroprevalence of Mycoplasma agassizii and tortoise herpesvirus in captive desert tortoises (Gopherus agassizii) from the Greater Barstow Area, Mojave Desert, California

Upper respiratory tract disease (URTD) has been implicated as a cause of decline of wild populations of desert tortoises, Gopherus agassizii, in the western Mojave Desert. One explanation for outbreaks of disease may be the release or escape of diseased captive tortoises into naïve wild populations. Because Mycoplasma agassizii and tortoise herpesvirus have surfaced as important pathogens, 179 captive tortoises were evaluated in the greater community of Barstow, San Bernardino County, California during 2000 and 2001 to determine pathogen exposure. An indirect enzyme-linked immunosorbent assay (ELISA) was performed to detect antibodies against Mycoplasma agassizii (n=179) and tortoise herpesvirus (n=109). Anti-mycoplasma antibodies were present in 82.7% of the tortoises while anti-herpesvirus antibodies were detected in 26.6%. A positive association was found between tortoises with anti-mycoplasma antibodies and severity of clinical signs of URTD (p=0.001) and with age categories, with adults being more likely to be positive (p<0.001). Neither association was found with herpesvirus exposure. No association was found between gender and pathogen exposure or between being positive for exposure to both pathogens. Findings suggest that captive tortoises can be a source of infection for free ranging desert tortoises.