Apparent lack of efficacy of toltrazuril against Eimeria species affecting brown kiwi (Apteryx mantelli) at a captive rearing facility

Abstract

AIM: To assess the efficacy of toltrazuril against the Eimeria spp. affecting brown kiwi (Apteryx mantelli).

METHODS: Droppings were collected from three brown kiwi, aged <6 months old, at a captive rearing facility in the North Island of New Zealand, between 22 February and 20 April 2017, on 14 sampling dates. Only droppings (n=30) that were excreted between 03:00 and 07:00, as determined using video surveillance, were included for analysis, reflecting the peak time for shedding of coccidial oocysts for brown kiwi. Oocysts were quantified in each sample and Eimeria species identified on the basis of oocyst morphology. All samples were collected between 2 and 10 days after the birds had been treated with 25 mg/kg toltrazuril.

RESULTS: Eimeria spp. oocysts were identified in 28/30 individual samples and on 14/14 sampling dates. Oocyst counts varied from 0 to 328,080 oocysts per gram (opg), and at least one oocyst count >10,000 opg was measured on 12/14 sampling dates. Three species of Eimeria were observed, with Eimeria apteryxii and E. kiwii most commonly encountered, whereas only one sample contained E. paraurii.

CONCLUSIONS AND CLINICAL RELEVANCE: In the three birds monitored at this research site, there was a high abundance of E. apteryxii and E. kiwii oocysts in droppings despite recent administration of toltrazuril. These results suggest that the populations of Eimeria spp. affecting brown kiwi at this location appear to possess an ability to survive exposure to toltrazuril. Toltrazuril is widely used at captive rearing facilities to limit the effects of coccidiosis in juvenile kiwi. If a lack of efficacy is confirmed, it will be necessary to investigate alternative treatment regimens alongside broader environmental management strategies.

KEY WORDS:

• Coccidia
• Eimeria
• kiwi
• Apteryx
• toltrazuril

Acknowledgements

The authors would also like to acknowledge the staff at the research site for allowing this research to be carried out within their Operation Nest Egg facilities as well as the contributions by their kiwi team staff.

ORCID

WE Pomroy http://orcid.org/0000-0003-2578-1678

Additional information

Funding

This research was funded through the Birds of New Zealand Research Fund, Ornithological Society of New Zealand; the Marion Cunningham Memorial Fund, Wildlife Society of the New Zealand Veterinary Association; the Massey University Foundation; the Massey University Summer Dissemination Grant for Master’s Research; and the Institute of Veterinary, Animal and Biomedical Sciences postgraduate research fund, Massey University.