27th Annual Meeting and Symposium of the
Desert Tortoise Council, March 22-24, 2002
Abstracts

Health Assessments of Captive and Wild Desert Tortoises at 17 Sites in the Mojave and Colorado Deserts, California

Kristin H. Berry, Ph.D.¹, Tracy Okamoto², Kemp Anderson³, Mary B. Brown, M.S., Ph.D.⁴; Lori Wendland, DVM⁴; and Francesco Origgi, DVM, Ph.D^5
1U. S. Geological Survey, 6221 Box Springs Blvd., Riverside, CA 92507; 
²Inyokern, CA 93527; 
³Long Beach, CA90803-4047; 
⁴Department of Pathobiology, College of Veterinary Medicine, University of Florida, Gainesville, FL; 
⁵Human Virology Unit, Department of Infectious Diseases and Immunology, San Raffaele Scientific Institute (Dibit), Via Olgettina 58, 20132 Milano, Italy

Between 1998 and 2001 we conducted in-depth health assessments of captive desert tortoises (Gopherus agassizii) at 2 desert towns and of wild desert tortoises at 15 field sites in the Mojave and Colorado deserts of California. Health assessments included collecting data on detailed clinical signs of health and disease, e.g., recording signs of upper respiratory tract disease (URTD), shell disease, and trauma; and taking blood and/or lymph samples and nasal lavages for laboratory analysis. The field health assessments were followed by analysis of tissue samples using enzyme-linked immunoassay (ELISA) and polymerase chain reaction (PCR) tests and cultures for Mycoplasma at the University of Florida. Some populations were tested for the herpesvirus using the new ELISA test developed by Dr. Origgi and others.

Using a combination of laboratory tests, 61.8% of captive tortoises from Ridgecrest and Inyokern (N = 34) and 60% of captive tortoises from Joshua Tree, Twentynine Palms, and Palm Springs (N = 30) tested positive for Mycoplasma agassizii and/or M. "mysteriosa". Most tortoises with positive clinical tests also showed multiple, moderate to severe clinical signs of URTD. The group of captive tortoises from the Joshua Tree, Twentynine Palms, and Palm Springs areas was also tested for herpesvirus and 32.1% had positive tests. Of the tortoises that tested positive for antibody to herpesvirus, 44.4% had concomitant positive tests for mycoplasma. In general, captive tortoises kept isolated from other captive tortoises and with a history of only one owner tested negative for mycoplasmosis and the herpesvirus.

Between 1997 and 1999, 142 samples were collected from 13 wild desert tortoises at seven plots (Tiefort, Alvord 6, Langford, Eastgate 1, Eastgate 2, Goldstone 12, Goldstone 15) within Ft. Irwin in the central Mojave Desert for URTD tests. Only one Goldstone plot produced positive samples (2 of 5 tortoises tested for both ELISA and cultures). Between 2000-2001, 121 samples were taken from 119 wild tortoises at 9 study plots from the western Mojave, central Mojave, northeastern Mojave, eastern Mojave, and northern Colorado deserts. Sites and sample sizes were Fremont Valley (N = 9), Ft. Irwin-Control (N = 20), Ft. Irwin-Tiefort (N = 17), Marine Corps Air Ground Combat Center (MCAGCC)-Sandhill (N = 25), Ord-Rodman (N = 12), Superior Cronese (N = 6), Ivanpah Valley (N = 16), Goffs (N = 6), and Ward Valley (N = 10). Samples were not necessarily available for all the tortoises for all the different URTD tests. None of the 119 tortoises tested positive for Mycoplasma agassizii and/or M. "mysteriosa." However, of 66 tortoises tested for herpesvirus, 6 (9%) were positive: 3 at MCAGCC-Sandhill, 2 at Ord-Rodman, and 1 at Ivanpah Valley. The sites where animals tested positive for herpesvirus were sites with higher sample sizes (N > 12). Twenty G₀ tortoises (see Medica et al., these abstracts) from the line-distance sampling projects at MCAGCC-Sandhill, Ord-Rodman, and Super-Cronese were tested for herpesvirus; of the 20, 4 (20%) tested positive.

Overall the percentages of captive tortoises with positive tests for one or more infectious diseases were considerably higher than percentages observed in the samples from most wild populations, a pattern reported by April Johnson et al. at this meeting and others in the literature. We recommend continued and more intensive sampling of desert tortoises for clinical signs of all significant diseases. We think all tortoises in research and monitoring programs should be tested using the available ELISA and PCR tests and cultures, and records should be kept and analyzed on patterns of clinical signs of disease. We recommend educating owners of captive tortoises about infectious diseases and providing protocols for quarantining individuals and segregating different species.

Acknowledgments: Financial support was provided by the U. S. Geological Survey, National Training Center at Ft. Irwin, and Marine Air Ground Task Force Training Command at Twentynine Palms. Thanks are due to Rhys Evans, Peter Woodman, Paul Frank, Rachel Woodard, and Taylor Edwards for field and clinical support.