Hookworm infection causes significant clinical disease and mortality in Australian sea lion pups (Neophoca cinerea). Pups are infected via the transmammary route during the immediate post-partum period with infection causing anaemia, enteritis, and reduced pup growth. All N. cinerea pups are infected and hookworm disease is estimated to contribute towards approximately 40% of all pup mortality, which oscillates between ~20–40%. The duration of patent hookworm infection is 2–3 months. As female N. cinerea demonstrate extreme natal site fidelity, and male pinnipeds are considered to be dead-end hosts for hookworm infection, we hypothesised that N. cinerea hookworm populations would be highly genetically structured. To better define the epidemiology of hookworm infection, we investigated the taxonomic identity, phylogenetic relationships, and diversity of hookworms from pups found dead (n=117) at three allopatric colonies in South Australia.
Morphological examination and molecular analyses of nuclear ribosomal loci (ITS1, ITS2, and 28s) demonstrated that a single, novel hookworm species, Uncinaria sanguinis, infects N. cinerea pups. Contrary to expectations, analysis of the mitochondrial cytochrome oxidase I gene (COI) revealed high hookworm diversity (h=0.986; π=0.013), unrelated to geographical location, with a large number of haplotypes (n=45).
The findings of this study challenge assumptions about the ecology of N. cinerea and the epidemiology of hookworm infection; in particular, the method/s of transmission and dispersal of hookworm between colonies. The results of further investigations to address the possibilities of patent adult infection, the New Zealand fur seal (Arctocephalus fosteri) as a means of hookworm dispersal, and paratenic hosts are presented and discussed. The characterisation of hookworm infection is vital to addressing key knowledge gaps relating to a significant disease threat; this study contributes towards our understanding of the N. cinerea–hookworm relationship, informing conservation of this endangered pinniped (IUCN Red List, 2008) and its parasitic fauna.