Assessment of Mojave Desert Tortoise Health Inside and Outside the Large-Scale Translocation Site
American Association of Zoo Veterinarians Conference 2019
Josephine Braun1, DrMedVet; Tristan Burgess2, BVSc, PhD; Carmel Witte1, MS, PhD; Nadine Lamberski3, DVM, DACZM, DECZM (Zoo Health Management); Roy Averill-Murray4, MS; Kimberleigh Field4, MS; Linda Allison4, MS; Bruce Rideout1, DVM, PhD, DACVP
1Disease Investigations, Institute for Conservation Research, San Diego Zoo Global, San Diego, CA, USA; 2Acadia Wildlife Services, South Freeport, ME, USA; 3Animal Health Department, San Diego Zoo Global, Escondido, CA, USA; 4Desert Tortoise Recovery Office, U.S. Fish and Wildlife Service, Reno, NV, USA


Desert tortoises (Gopherus agassizii) are impacted by continuous habitat loss and fragmentation. This study assesses health risks from improving connectivity between populations inside and outside the enclosed Large-scale Translocation Site (LSTS), Ivanpah Valley, Nevada. The LSTS was a recipient site for desert tortoises with diverse backgrounds. A total of 421 tortoises with health assessments in 2016 (T2) and a subset of 196 tortoises with prior health assessments between 2011 and 2014 (T1) were evaluated. The focus was on upper respiratory tract disease (URTD) caused by Mycoplasma agassizii and M. testudineum. Clinical signs were recorded at field health assessments. Infection status was determined by quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA). Multiple logistic regression was used to estimate associations while controlling for covariates. LSTS had the highest prevalence of M. agassizii (25%), M. testudineum (3.0%), and clinical signs (18.9%) in 2016, and the highest incidence of M. agassizii infection (p<0.0001). Presence of any clinical sign was positively associated with M. agassizii infection (OR=7.7, p<0.0001) but not with study site (p≥0.127). There was no association with M. testudineum infection (p=0.360). An estimated 3.2% of tortoises converted from M. agassizii negative to positive between T1 and T2. This conversion was associated with increased prevalence of clinical signs at T2 (OR=11.1, p=0.018). While M. agassizii and URTD are present inside and outside the LSTS, there is a possibility that incidence of M. agassizii infection and URTD would increase outside of LSTS if the two populations were to reconnect. The degree of risk and long-term population impact remain unknown.


The authors thank the Molecular Diagnostics Lab for sample processing; Lori Scott for pulling data; Kristina Drake, Dana Hinderle, and Chris Blandford for submitting data; Terry Christopher (Great Basin Institute) for collecting T2 LSTS samples; and Robert Cooper for help with pulling samples.


Speaker Information
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Josephine Braun, DrMedVet
Disease Investigations
Institute for Conservation Research
San Diego Zoo Global
San Diego, CA, USA

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