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.
This thesis comprises published works. Due to copyright restriction they are not included here but can be accessed from the publisher:
Taylor H. S, Morgan, K. J., Pomroy, W. E., McInnes, K., & Lopez-Villalobos, N. (2018, September 1). The circadian variation of oocyst shedding of Eimeria spp. affecting brown kiwi (Apteryx mantelli). Parasitology Research, 117(9), 2997-3001. doi:10.1007/s00436-018-5945-0
Taylor H. S, Morgan, K. J., Pomroy, W. E., & McInnes, K. (2019, March 1). Apparent lack of efficacy of toltrazuril against Eimeria species affecting brown kiwi (Apteryx mantelli) at a captive rearing facility. New Zealand Veterinary Journal, 67(2), 101-104. doi:10.1080/00480169.2018.1541425