28th Annual Meeting and Symposium of the
Desert Tortoise Council, February 21-23, 2003
Abstracts

Health Assessments of Captive and Wild Desert Tortoises at 26 Sites in the Mojave and Colorado Deserts, California, in 2002

Kristin H. Berry, Ph.D.¹, Mary B. Brown, M.S., Ph.D.²; Lori Wendland, DVM², Francesco Origgi, DVM, Ph.D.³, April Johnson, DVM⁴ with Kemp Anderson⁵, Tracy Bailey⁶, Peter Woodman⁷, and Rhys Evans^8
1U. S. Geological Survey, 6221 Box Springs Blvd., Riverside, CA 92507; 
²Department of Pathobiology, ⁴Department of Small Animal Clinical Sciences: College of Veterinary Medicine, University of Florida, Gainesville, FL; 
³Human Virology Unit, Department of Infectious Diseases and Immunology, San Raffaele Scientific Institute (Dibit), Via Olgettina 58, 20132 Milano, Italy
⁵Seal Beach, CA; ⁶Inyokern, CA; ⁷Kiva Biological Consulting, Inyokern, CA;
⁸Marine Corps Air Ground Task Force Training Center, 29 Palms, CA

Between 1998 and 2002 we conducted in-depth health assessments of captive desert tortoises (Gopherus agassizii) at 2 desert towns and of wild desert tortoises at 26 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; this test has not yet been validated. In 2002, field sampling was markedly enhanced by using two teams of field biologists. The first team located the tortoises and the second team, with expertise in drawing blood and collecting the nasal lavages, followed and took samples.

In 2002, samples were collected from 225 wild desert tortoises at 19 plots from the western Mojave, central Mojave, northeastern Mojave, eastern Mojave, northern and eastern Colorado deserts. Sites and sample sizes were Desert Tortoise Research Natural Area , Sites 3 and 4 (N = 3, 22), Fremont-Kramer (N = 9), Ft. Irwin-Control (N = 20), Ft. Irwin-Tiefort (N = 19), FISS (N = 3), Marine Corps Air Ground Combat Center (MCAGCC)-Sandhill (N = 24), MCAGCC-Lavic (N = 10), MCAGCC-Bullion (N = 7 ), Ord-Rodman (N = 14), Superior Cronese (N = 9), Ivanpah Valley-Site 14 and G0 (N = 11, 16), Fenner Valley (N = 6), Chemehuevi (N =12), Lucerne Valley (N = 7 ), Shadow Valley (N = 3), and Ward Valley (N = 6). As in previous surveys, samples were not necessarily available for all the tortoises for all the different tests and not all of the laboratory samples have been analyzed. Six tortoises tested positive for Mycoplasma agassizii and/or M. cheloniae, prop. nov. sp. out of 198 tortoises with ELISA tests and 178 with cultures. Of the 149 tortoises with herpes test results now available, 48% tested positive for herpesvirus. One hundred twenty-six tortoises were from nine sites in the line-distance sampling projects at Fremont-Kramer, MCAGCC-Sandhill, MCAGCC-Lavic, Ord-Rodman, Superior-Cronese, Ivanpah Valley, Fenner Valley, Chemehuevi, and Chocolate Mountains Aerial Gunnery Range. Some of the tortoises were G₀ tortoises and some were captured opportunistically nearby. None tested positive for Mycoplasma. However, of 101 tortoises with herpesvirus ELISA tests, 51% tested positive, a higher percentage than in 2001.

The 2002 results can be compared with two older data sets: (1) 141 samples taken from 131 desert tortoises between 1997 and 1999 at 7 plots on the Ft. Irwin National Training in the central Mojave Desert; and (2) 121 samples from 119 wild tortoises at 9 study plots from the western Mojave, central Mojave, northeastern Mojave, eastern Mojave, and northern Colorado. Samples were not necessarily available for all the tortoises for all the different URTD tests or for the herpes virus tests. For the first data set, only one plot at Goldstone produced positive samples (2 of 5 tortoises tested for both ELISA and cultures). For the second data set, none of the 119 tortoises tested positive for Mycoplasma agassizii and/or M. cheloniae, prop. nov. sp. 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 from the line-distance sampling projects at MCAGCC-Sandhill, Ord-Rodman, and Superior-Cronese were tested for herpesvirus; of the 20, 4 (20%) tested positive.

The wild desert tortoises we have sampled have lower percentages of positive URTD tests than the captive tortoises sampled at Ridgecrest/Inyokern (N = 34) and Joshua Tree/Twentynine Palms/Palm Springs (N =30). Using a combination of laboratory tests, 61.8% of captive tortoises from Ridgecrest and Inyokern and 60% of captive tortoises from Joshua Tree, Twentynine Palms, and Palm Springs (N = 30) tested positive for Mycoplasma agassizii and/or M. cheloniae prop. nov. sp.. 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. Our findings on captive tortoises are similar to those reported by April Johnson et al. in 2001 at the Desert Tortoise Council Symposium and others in the literature.

We recommend continued and more intensive sampling of desert tortoises for clinical signs of all significant diseases. We reiterate previous recommendations that 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 education programs for owners of captive tortoises about infectious diseases, development of protocols for quarantining individuals and segregating different chelonian species, and development of action plans to prevent escape or deliberate releases of captive tortoises to the wild.

Acknowledgments: Financial support was provided by the U. S. Geological Survey, California Department of Fish and Game, National Training Center at Ft. Irwin, Marine Air Ground Task Force Training Command at Twentynine Palms, and Desert Tortoise Preserve Committee. For field support, thanks are due to Paul Frank, Rachel Woodard, Tim Shields, Taylor Edwards and a host of new tortoise biologists eager to learn about health evaluations.