Josephine Braun
Carmel L Witte
Nadine Lamberski
Field. Kimberleigh J
Linda J. Allison
Roy C. Averill-Murray
K. Kristina Drake
Kenneth E. Nussear
Todd Esque
Bruce A Rideout
Tristan L. Burgess
2021
<p><span>The Mojave Desert tortoise (</span><i>Gopherus agassizii</i><span>), federally listed as threatened, has suffered habitat loss and fragmentation due to human activities. Upper respiratory tract disease (URTD), a documented health threat to desert tortoises, has been detected at the Large-Scale Translocation Study Site (LSTS) in southwestern Nevada, US, a fenced recipient site for translocated animals. Our study aimed to 1) estimate prevalence of URTD and </span><i>Mycoplasma</i><span> infection at LSTS and three nearby unfenced sites; 2) assess whether </span><i>Mycoplasma</i><span> infection status was associated with developing clinical signs of URTD; and 3) determine whether such an association differed between LSTS and unfenced areas. We sampled 421 tortoises in 2016 to describe the current status of these populations. We evaluated three clinical signs of URTD (nasal discharge, ocular discharge, nasal erosions) and determined individual infection status for </span><i>Mycoplasma agassizii</i><span> and </span><i>Mycoplasma testudineum</i><span> by quantitative PCR and enzyme-linked immunosorbent assay. In 2016, LSTS had the highest prevalence of </span><i>M. agassizii</i><span> (25.0%; 33/132), </span><i>M. testudineum</i><span> (3.0%; 4/132), and URTD clinical signs (18.9%; 25/132). Controlling for other factors, clinical sign(s) were positively associated with </span><i>M. agassizii</i><span> infection (odds ratio [OR]=7.7, </span><i>P</i><span>=0.001), and this effect was similar among study sites (</span><i>P</i><span>>0.99). There was no association with </span><i>M. testudineum</i><span> status (</span><i>P</i><span>=0.360). Of the 196 tortoises in a longitudinal comparison of 2011–14 with 2016, an estimated 3.2% converted from </span><i>M. agassizii</i><span>-negative to positive during the study period, and incidence was greater at LSTS (</span><i>P</i><span>=0.002). Conversion to positive </span><i>M. agassizii</i><span> status was associated with increased incidence of clinical signs in subsequent years (OR=11.1, </span><i>P</i><span>=0.018). While </span><i>M. agassizii</i><span> and URTD are present outside the LSTS, there is a possibility that incidence of </span><i>Mycoplasma</i><span> infection and URTD would increase outside LSTS if these populations were to reconnect. Population-level significance of this risk appears low, and any risk must be evaluated against the potential long-term benefits to population viability through increased connectivity.</span></p>
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10.7589/JWD-D-20-00140
en
Wildlife Disease Association
Assessment of disease risk associated with potential removal of anthropogenic barriers to Mojave desert tortoise (Gopherus agassizii) population connectivity
article