Coccidia of the endangered South Island Takahē (Porphyrio hochstetteri) : investigations of pathobiology and management : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Veterinary Science in Wildlife Health at Massey University, Manawatū, New Zealand
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Date
2018
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Massey University
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Abstract
The South Island Takahē (Porphyrio hochstetteri) is a large flightless rail, endemic to New
Zealand currently listed as endangered with a population numbering approximately 340
individuals. The intensive management programme for this species has seen a modest
increase in the population and includes strategies such as captive rearing for release at
protected sites and numerous translocations of birds between these sites each year to
maximise genetic diversity. This interconnectedness of geographically dispersed
populations and critical points of high stocking density contribute to the potential for
spread of infectious disease. Coccidian oocysts have been detected in Takahē faecal
samples for decades and sporadically coccidia were implicated in the death of Takahē.
By early 2015 concerns were being raised about markedly elevated individual faecal
oocyst counts and the apparent failures of treatment with toltrazuril. The potential for
significant negative impacts of coccidia in terms of both clinical disease and sub-clinical
effects on juvenile growth rates and fertility led to the investigations reported in this
thesis into the coccidia affecting Takahē.
A novel Eimeria sp. is described from a Takahē host. Based on morphological
characteristics this coccidian species is distinct from other Eimeria spp. described in
hosts of the family Rallidae. A survey of stored historical faecal samples and
contemporary routine screening samples demonstrated the presence of this Eimeria sp.
across most of the fragmented conservation management network for Takahē.
Modification of treatment protocols and management actions was closely associated
temporally with a sustained reduction in the Eimeria sp. shedding rates at a breeding
facility central to the Takahē population network. Preliminary results were supportive
of the existence of a diurnal shedding pattern for the Eimeria sp. with a peak of oocyst
shedding in the late afternoon after 3pm in winter, which has implications for the
collection of screening samples and the interpretation of results collected at different
times of day. Concurrent to these investigations into the biology of the Takahē coccidia,
trials were carried out to establish the safety of the anti-coccidial medication,
decoquinate, in Takahē. No clinically significant deleterious effects were found in the
parameters examined.
The findings presented are initial investigations into an Eimeria sp. from a Takahē host,
the effectiveness of control measures implemented and safety of potential
management options. The crisis of regular extreme oocyst counts in Takahē, which
prompted this research, was resolved, however the potential for a recurrence is ever
present in a species conservation programme that relies on intensive breeding and
translocation of individuals. This research is the foundation for future research into the
characterisation and management of Eimeria spp. in Takahē.
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Keywords
Takahe, Diseases, Rare birds, New Zealand|, Fiordland, Coccidiosis in animals, Eimeria