Managing a Tuberculosis Outbreak: Development and Implementation of Screening Protocols for Mycobacterium tuberculosis in Zoo Mammals
Frances Hulst, BVSc, MVS; Larry Vogelnest, BVSc, MVS, MACVSc; Kimberly Vinette Herrin, MS, DVM; Cheryl Sangster, BSc, DVM, MVSc, DACVP; Paul Thompson, DHSc, BMedSc, MSc
Tuberculosis (TB) due to Mycobacterium tuberculosis was diagnosed in an Asian elephant (Elephas maximus) and a chimpanzee (Pan troglodytes) at Taronga Zoo, Australia. Detailed investigation into the disease outbreak included development of screening protocols for TB in all collection mammals. Early, rapid detection of disease is essential to prevent the silent spread of TB through a collection and to protect the health of staff and visitors. Ante-mortem diagnosis of TB in zoo animals is challenging due to lack of validated or standardized diagnostic techniques in most species and the limited sensitivity and specificity of most tests.
Over 600 animals of 78 species were prioritized for TB screening based on reported susceptibility to M. tuberculosis, exposure risk, availability of a recognized testing protocol and logistics of animal restraint. Where possible, a combination of diagnostic test modalities was used for each species, including non-specific tests (clinical examination, CBC and serum biochemistry, radiography, gross necropsy); direct sampling for organisms (Ziehl-Neelsen staining, PCR and culture of tracheo-bronchial lavage, trunk wash or nasal wash material, fine needle aspirates of lymph nodes or tissue collected at necropsy); and immunologic tests based on cell mediated immune response (comparative tuberculin skin test and Interferon-γ release assay) or humoral response (Elephant TB Stat-Pak® (Chembio) or Dual Path Platform Vet®TB test™ (Chembio)). Suspect or positive results were interpreted in light of the potential limitations of the tests and prompted further investigation. The zoo’s long term TB surveillance program will be modified according to the results of ongoing screening and exposure risk.
The authors wish to thank the zookeepers and Taronga Wildlife Hospital veterinary nurses who provided assistance with animal procedures.