Nematode infections of kiwi (Apteryx spp.) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Palmerston North, New Zealand
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Date
2021
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Massey University
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Abstract
Overall, little is known about the nematodes of kiwi (Apteryx spp.) and there has, thus far, been little indication that such infections are associated with significant clinical disease in these species. However, over the past 15 to 20 years there has been increasing recognition of cases of nematode larva migrans identified in kiwi at necropsy, caused by the aberrant migration of nematode larvae within visceral organs and brain. The initial study of this research re-examines archived cases of larva migrans through DNA extraction and PCR using formalin-fixed, paraffin-embedded tissue sections. Sequencing and BLAST analysis of positive results showed 100% alignment to database sequences from Toxocara cati, a nematode parasite whose definitive host is the domestic cat, indicating an infection acquired from an invasive mammalian species. Following the success of this methodology, similar techniques were applied to archived biopsies from an outbreak of cutaneous nematodiasis in a geographically isolated population of juvenile rowi kiwi (Apteryx rowi). The resultant sequences aligned among members of the capillarid genus Eucoleus although without an exact match present in the database, and so the precise, species-level identification and original source of this unusual presentation of cutaneous capillariasis remains unknown. Concurrent with these investigations into aberrant nematode infections, an opportunistic, prospective survey that included 50 kiwi presenting for necropsy examination was performed, with the objective of examining as far as practicable the prevalence, diversity, and potential pathogenicity of gastrointestinal nematodes, including any potential association with aberrant migratory lesions. The results confirmed that gastrointestinal nematodiasis was common, with 94% of the kiwi examined infected to some degree, and at least five morphologically distinct nematode types were found. Species-level identification of the nematodes was not reached based on limited morphological and molecular evaluations. However, while such gastrointestinal nematode infections appeared on the whole to be well-tolerated by the kiwi hosts, occasional cases of significant ventriculitis were identified in association with gizzard infections, particularly in juvenile, captive-bred kiwi. Furthermore, histological lesions consistent with nematode larva migrans were identified in around 43% of the survey kiwi in which visceral sections were also examined, indicating that this disease may be routinely under-diagnosed.
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Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author.
Keywords
Parasites, Diseases, Nematodes