Disease in wildlife or exotic species
Retrospective Survey of Amphibian Pathology Cases at Texas A&M University System (2016–2020)

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Summary

Dramatic declines in amphibians worldwide highlight the need for a better understanding of diseases affecting these species. To delineate the health issues of amphibians submitted to Texas A&M University System (2016–2020), the databases were queried on the basis of defined selection criteria. A total of 502 anurans (157 frogs [44 species] and 345 toads [10 species]) and 30 caudatans (23 salamanders [6 species] and 7 newts [4 species]) were reviewed. A most likely cause of death or major pathological finding (CD-MPF) leading to euthanasia was identified in 295 (55%) Anura cases and 15 (50%) Caudata cases. Of the 532 records reviewed, anurans included 492 captive, seven free-ranging and three undetermined specimens. All caudatans were captive. The most common CD-MPF in anurans was infectious/inflammatory (228/295; 77%), involving mycobacteriosis (73/228; 32%), chlamydiosis (44/228; 19%) and mycosis (32/228; 14%). Neoplasia was less common (28/295; 9%). Infectious/inflammatory lesions (14/15; 93%) were the main CD-MPFs in caudatans. Infectious diseases are a significant threat to captive amphibians in Texas and these results may aid personnel involved in amphibian conservation programmes, veterinarians and diagnosticians.

Introduction

Amphibians (∼7,600 species) are widespread vertebrates that include the orders Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians). Rapid declines in populations worldwide have led to increased interest in amphibian epidemiology and disease (Grant et al, 2020). Environmental pollution, habitat loss, introduction of prey species, climate change, overexploitation and infectious diseases are their main threats worldwide (Earl et al, 2016; Scheele et al, 2019). Therefore, ex-situ conservation and research programmes using wild-captured specimens have increased significantly (Biega et al, 2017; Jacken et al, 2020). An increased understanding is essential to improve management and maximize amphibian conservation efforts. In this study, we evaluated and delineated the main pathologies and causes of mortality in amphibians submitted to the Texas A&M University System between 2016 and 2020.

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Materials and Methods

The databases of the Texas A&M Veterinary Medical Diagnostic Laboratory and the Department of Veterinary Pathobiology were interrogated on the basis of defined selection criteria. Key words employed were ‘amphibian’, ‘frog’, ‘toad’, ‘salamander’ and ‘newt’. Records from January 2016 to August 2020 were analysed. Epidemiological and biological data, necropsy reports, photographic material and ancillary diagnostic results were retrieved and further evaluated, with special emphasis on the type and

Results

A total of 532 amphibian records representing 64 species were evaluated: 502 anurans (order Anura) (157 frogs [44 species] and 345 toads [10 species]) and 30 caudatans (order Caudata) (23 salamanders [6 species] and 7 newts [4 species]). The most commonly submitted species were the Houston toad (Anaxyrus houstonensis; n = 325), African clawed frog (Xenopus laevis; n = 16), Lemur leaf frog (Hylomantis lemur; n = 16) and Barton spring salamander (Eurycea sosorum; n = 15). Sex distribution for

Discussion

Very few studies have reported causes of death in large amphibian cohorts (Reiehenbach-Klinke and Elkan, 1965; Elkan, 1976; Green and Sherman, 2001; Eustace et al, 2018; Flach et al, 2020). Our findings indicate that infectious diseases are the main disease threats to captive amphibians in Texas. The Houston toad, an endangered species, is severely impacted, with mycobacteriosis and chlamydiosis as the leading causes of morbidity and mortality.

Amphibian mycobacteriosis has a worldwide

Acknowledgments

The authors would like to thank the dedicated staff at the Houston Zoo for their remarkable care for these animals and the histology technicians at Texas A&M Veterinary Medical Diagnostic Laboratory for their professionalism and commitment.

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