A retrospective study of post-mortem examination findings in takahe (Porphyrio hochstetteri)

A retrospective study of post-mortem examination findings in takahe (Porphyrio hochstetteri)
Peer reviewed

Abstract

AIMS: To identify the major diseases or disease processes affecting both captive and wild populations of takahe (Porphyrio hochstetteri) in birds submitted for post-mortem examination between 1992 and 2007, and to survey archived wild dead takahe for the presence of Erysipelothrix rhusiopathiae.

METHODS: Reports of 199 post-mortem examinations submitted between 1992 and 2007 were reviewed retrospectively. The reports comprised 56 eggs, 51 chicks up to 6 months of age, 13 sub-adults 6-18 months old, 74 adults and five birds where age was not recorded. Bone marrow flushed from the keel of 34 frozen adult takahe was assayed for the presence of E. rhusiopathiae, using PCR analysis.

RESULTS: Of the eggs examined, 6/56 (11%) had no recorded diagnosis, 24/56 (43%) were infertile and 26/56 (46%) showed embryonic mortality at various stages. Excluding eggs, the cause of death could not be determined in 64/138 (46%) birds with a recorded age that were examined. Contributing factors for the low rate of diagnosis included advanced decomposition of many carcasses, the freezing of some birds prior to pathological investigation, long delays between recovery and submission for post-mortem examination, and variation in the extent of post-mortem examination and ancillary diagnostic testing. Common post-mortem examination findings in chicks included those related to cardiac disease [11/51 (22%)], infectious or inflammatory disease [9/51 (18%)] and trauma [7/51 (14%)]. In adult birds, the most common post-mortem examination findings were due to infectious or inflammatory disease [15/74 (20%)] including septicaemia due to E. rhusiopathiae [3/74 (7%)], followed by degenerative conditions due to diet, age and husbandry [9/74 (12%)]. Bacteria implicated in the causes of death included Escherichia coli, E. rhusiopathiae, Salmonella enterica serovar Typhimurium, and Pseudomonas aeruginosa. Only 1/34 (3%) of the frozen carcass examined using PCR was positive for E. rhusiopathiae.

CONCLUSIONS: This study highlights a need for improved recovery, storage and submission of dead takahe for pathological examination; consistency in post-mortem examination, ancillary testing and recording of findings; and finally, regular communication between wildlife pathologists, conservation workers and representatives of Ngai Tahu.

KEY WORDS: Post mortem, necropsy, takahe, Porphyrio hochstetteri, Erysipelothrix rhusiopathiae, egg infertility, angular limb deformity, taonga


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