Aspergillosis in hihi (Notiomystis cincta) on Mokoia Island

An intensive 2-year field study of 65 hihi (or stitchbirds) on Mokoia Island provided an opportunity to investigate the causes of mortality of this endangered species in a free-living environment.

The birds were observed daily during the breeding season (October to March) and every 4 weeks during the remainder of the year. Any abnormalities in behaviour, voice and body weight were recorded and all sick or dead birds which could be recovered were taken to the laboratory for necropsy.

Thirty-one birds died during the period of this study. Aspergillosis was found to be the cause of death in six of nine adult birds examined post mortem. Some of the affected birds experienced subtle voice changes before becoming ill and all birds had granulomatous lesions in airsacs or lungs at necropsy. A further eight birds for which carcasses could not be found or which were autolysed showed similar clinical signs before death or disappearance.

Because Aspergillus is an opportunist pathogen it seems likely that affected birds were immunosuppressed. This may have occurred during the breeding season which in this species is highly stressful. The presence of fungal material in bronchial exudate and the occurrence of the disease in mates, raises the possibility that aspergillosis in hihi may be contagious.