Diagnosis, Treatment, Monitoring and Release Implications of Chlamydophila-Associated Encephalitis in Houston Toads (Anaxyrus [Bufo] houstonensis)
American Association of Zoo Veterinarians Conference 2013
Lauren L. Howard1, DVM, DACZM; Allan P. Pessier2, DVM, DACVP; Paul S. Crump3, BS; Cassidy Johnson1, PhD; Tyler Parker1; Anibal G. Armien4, DVM, MSc, PhD, DACVP; Fabiano Oliveira5, DVM, DACVP; Paula Ciembor6, DVM, PhD; Branson W. Ritchie6, DVM, PhD
1Houston Zoo, Inc., Houston, TX, USA; 2Wildlife Disease Laboratories, Institute for Conservation Research, San Diego Zoo Global, San Diego, CA, USA; 3Biology Department, Canadian Rivers Institute, University of New Brunswick–Saint John, Saint John, NB, Canada; 4Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA; 5Texas A&M Veterinary Medical Diagnostic Laboratory, College Station Laboratory, College Station, TX, USA; 6Infectious Diseases Laboratory, Department of Small Animal Medicine, University of Georgia, Athens, GA, USA


The Houston Zoo participates in a local conservation program for the endangered Houston toad (Anaxyrus [Bufo] houstonensis) through hormone-assisted captive propagation, maintenance of a captive assurance colony, and collection of eggs from the wild for head starting/release purposes. In spring 2012, 42% (22/52) of young toads from an indoor, captive bred group presented either neurologic signs such as head pressing and abnormal gait or acute death. Histologically, these toads had marked encephalomyelitis associated with an intracellular organism morphologically consistent with Chlamydophila sp., which was confirmed via electron microscopy. Preliminary molecular evaluation suggested that chlamydial isolates from nervous tissue of affected toads were most consistent with C. pneumoniae. A polymerase chain reaction (PCR)-based assay was used to determine the most clinically relevant samples for screening toads for chlamydial nucleic acid. The clinical and histologic changes, and treatment and pre-release screening protocols we developed for screening toads for this chlamydial organism will be presented. Further inquiry will include identification of the strain of C. pneumoniae and an epidemiologic investigation to identify the possible source of infection.


The authors would like to thank the staff at the University of Georgia Infectious Diseases Laboratory for their continued diligence in processing toad samples. Thanks also to Houston Zoo, Inc. staff: registered veterinary technicians Karina Vercic, Ryanne Henigar and Eva Smoot, and administrative assistants Lindsey Parker and Kathryn Lippman for assistance with sample collection, organization, and shipping.


Speaker Information
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Lauren L. Howard, DVM, DACZM
Denton A. Cooley Animal Hospital
Houston Zoo, Inc.
Houston, TX, USA

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