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Has files: YesSubject: search.filters.subject.Coccidiosis in animals

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    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
    (Massey University, 2018) Jolly, Megan Jayne
    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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    The Eimeria species affecting brown kiwi : host-parasite interactions and conservation implications : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Manawatu, New Zealand
    (Massey University, 2017) Taylor, Harry Stewart
    Brown kiwi (Apteryx mantelli) are a threatened flightless nocturnal ratite endemic to New Zealand. The conservation of this species currently utilises a recovery programme known as ‘Operation Nest Egg’ (ONE) to increase numbers of brown kiwi in the wild. However, ONE results in a high density of immunologically naïve kiwi being housed in semi-captive conditions with the potential to result in significant morbidity, and occasionally mortality, from coccidiosis caused by multiple species of Eimeria. The aim of this research was to describe any circadian variation in oocyst shedding occurring for the Eimeria spp. affecting brown kiwi. Dropping samples were collected from brown kiwi at an ONE site using video surveillance to determine the time of excrement. Oocyst counts were carried out on these droppings and analysed in relation to the time of excrement and the days since the most recent toltrazuril application. The results show that two of the Eimeria spp. affecting brown kiwi exhibit circadian variation in oocysts shedding. Oocyst counts for each of the one hour time slots starting at 3am, 4am, 5am and 6am were significantly (p<0.05) higher than each of the time slots starting at 8pm, 9pm, 10pm and 11pm. This indicates that peak oocyst shedding occurs between 3am and 7am, with few or no oocysts shed between 8pm and 12pm. The results also suggest high prevalence and abundance of Eimeria spp. oocysts in the droppings, with 91% of samples from during peak shedding being positive for Eimeria spp., despite recent toltrazuril administration. These findings have several important implications for the conservation of brown kiwi. The reported circadian variation may affect the accuracy of coccidia testing and provides insight into the evolution of this adaptive trait in coccidia. The apparent lack of efficacy of toltrazuril may have management implications and requires further research. The results of this research increase our understanding of the biology of the Eimeria spp. affecting brown kiwi. Continuing to improve our understanding of host-parasite interactions is vital to enable effective disease management in order to reduce the detrimental impact of coccidia on ONE and ensure the ongoing success and sustainability of this important conservation programme.
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    Epidemiology of coccidiosis in calves and control of coccidiosis using toltazuril at the time of weaning : this thesis is presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Veterinary Parasitology at Massey University, Palmerston North, New Zealand
    (Massey University, 2005) Gaddam, Mary Jones
    Two separate studies were conducted to investigate the impact of coccidiosis in young calves. In one study calves were reared to weaning (100kg liveweight) by feeding meal with or without monensin added. The oocyst counts were low in both groups up to weaning and there was no statistically significant (p<0.05) improvement in terms of body weight or a decline in oocyst counts in the monensin-treated group At weaning a single dose of toltrazuril (20mg/kg) was given to half the calves in both groups. A similar treatment regime was given in a second study where calves had been raised to weaning by commercial calf rearers. Half of these were treated with toltrazuril (20mg/kg) and half not. In both studies there was a statistically significant (p<0.001) reduction in oocyst counts in treated calves which remained very low for 4-5 weeks post treatment. The treatment also significantly increased (p<0.001) weight gains in treated calves by 3-5kgs at 5-6 weeks post treatment. The coccidial status of other calves on a variety of farms were also monitored including a group of organic beef farms. High oocyst counts were noted on occasions where calves were not on anti-coccidial treatment. Low oocyst counts were noted in adult cows where they were examined. The two most prevalent species overall were Eimeria zuernii (95%) and E. bovis (87%) followed by E. auburnensis (62%), E. cylindrica (42%), E. canadensis (31%), E. wyomingensis (23%), E bukidnonensis (36%), E. ellipsoidalis (24%) E. alabamensis (12%), E. brasiliensis (12%), and E. subspherica (27%). The most predominant species, measured as the most numerous oocysts overall, were E. bovis (31%) followed by E. zuernii (27%), E. auburnensis (13%), E. bukidnonensis (7%), E. cylindrica (6%), E. wyomingensis (5.3%), E. canadensis (4.4%), E. ellipsoidalis (3.3%), E. brasiliensis (1.9%), E. subspherica (1.5%), and E. alabamensis (1%). The most prevalent species were also the most pathogenic species. On many occasions calves were infected with more than one species, sometimes as many as 5-6 Eimeria species. A redescription of the 11 species of Eimeria in cattle identified from New Zealand Farms was made.