Hookworm infection, anaemia and genetic variability of the New Zealand sea lion

Hookworms are intestinal blood-feeding nematodes that parasitize and cause high levels of mortality in a wide range of mammals, including otariid pinnipeds. Recently, an empirical study showed that inbreeding (assessed by individual measures of multi-locus heterozygosity) is associated with hookworm-related mortality of California sea lions. If inbreeding increases susceptibility to hookworms, effects would expectedly be stronger in small, fragmented populations. We tested this assumption in the New Zealand sea lion, a threatened otariid that has low levels of genetic variability and high hookworm infection rates. Using a panel of 22 microsatellites, we found that average allelic diversity (5.9) and mean heterozygosity (0.72) were higher than expected for a small population with restricted breeding, and we found no evidence of an association between genetic variability and hookworm resistance. However, similar to what was observed for the California sea lion, homozygosity at a single locus explained the occurrence of anaemia and thrombocytopenia in hookworm-infected pups (generalized linear model, F = 11.81, p < 0.001) and the effect was apparently driven by a particular allele (odds ratio = 34.95%; CI: 7.12–162.41; p < 0.00001). Our study offers further evidence that these haematophagus parasites exert selective pressure on otariid blood-clotting processes

Causes of neonatal mortality in the New Zealand sea lion (Phocarctos Hookeri) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Pathology at Massey University, Palmerston North, New Zealand

As part of a health survey of New Zealand sea lions (Phocarctos hookeri) on Enderby Island, Auckland Islands (50°30’S, 166°17’E), neonatal mortality was continuously monitored at the Sandy Bay Beach rookery, from 1998/1999 to 2004/2005. The primary causes of death were categorised as trauma (35%), bacterial (24%) and hookworm (13%) infections, starvation (13%) and stillbirth (4%). During the 2001/2002 and 2002/2003 breeding seasons, bacterial epidemics caused by Klebsiella pneumoniae increased mortality by three times the mean in non-epidemic years. Uncinaria spp. from New Zealand sea lion (NZSL) pups was described for the first time using morphometric criteria. It differed from the two species already described in pinnipeds, Uncinaria lucasi and Uncinaria hamiltoni, suggesting the existence of a different morphotype in NZSLs. A study on the epidemiology of hookworm infection showed that all pups up to at least three months of age harboured adult hookworms in their intestines and transmammary transmission was identified as the route of infection of NZSL pups. Uncinariosis as a primary cause of mortality was generally associated with anaemia, haemorrhagic enteritis and frank blood in the lumen. The relationship between hookworm burden and clinical disease could not be clearly established. The 2001/2002 and 2002/2003 bacterial epidemics at Sandy Bay Beach rookery were caused by a clonal strain of Klebsiella pneumoniae as verified by pulse-field gel electrophoresis and antimicrobial testing. Suppurative arthritis was the most common post-mortem diagnosis during the two epidemic seasons. Internal lesions were consistent with septicaemia, which explained the wide range of organs from which the pathogen was grown in pure culture. A serological test investigating the exposure of NZSLs to Klebsiella spp. showed that the large majority of pups up to two months of age did not have any anti-Klebsiella antibodies, even after the epidemics, but that almost all the adults were seropositive. In addition, passive immunoglobulin (Ig) transfer from lactating females to neonates was examined by measuring IgG levels in pups and was very low compared to terrestrial mammals although similar to other pinniped neonates

Molecular Systematics of Pinniped Hookworms (Nematoda: \u3ci\u3eUncinaria\u3c/i\u3e): Species Delimitation, Host Associations and Host-Induced Morphometric Variation

Hookworms of the genus Uncinaria have been widely reported from juvenile pinnipeds, however investigations of their systematics has been limited, with only two species described, Uncinaria lucasi from northern fur seals (Callorhinus ursinus) and Uncinaria hamiltoni from South American sea lions (Otaria flavescens). Hookworms were sampled from these hosts and seven additional species including Steller sea lions (Eumetopias jubatus), California sea lions (Zalophus californianus), South American fur seals (Arctocephalus australis), Australian fur seals (Arctocephalus pusillus), New Zealand sea lions (Phocarctos hookeri), southern elephant seals (Mirounga leonina), and the Mediterranean monk seal (Monachus monachus). One hundred and thirteen individual hookworms, including an outgroup species, were sequenced for four genes representing two loci (nuclear ribosomal DNA and mitochondrial DNA). Phylogenetic analyses of these sequences recovered seven independent evolutionary lineages or species, including the described species and five undescribed species. The molecular evidence shows that U. lucasi parasitises both C. ursinus and E. jubatus, whereas U. hamiltoni parasitises O. flavescens and A. australis. The five undescribed hookworm species were each associated with single host species (Z. californianus, A. pusillus, P. hookeri, M. leonina and M. monachus). For parasites of otarids, patterns of Uncinaria host-sharing and phylogenetic relationships had a strong biogeographic component with separate clades of parasites from northern versus southern hemisphere hosts. Comparison of phylogenies for these hookworms and their hosts suggests that the association of U. lucasi with northern fur seals results from a host-switch from Steller sea lions. Morphometric data for U. lucasi shows marked host-associated size differences for both sexes, with U. lucasi individuals from E. jubatus significantly larger. This result suggests that adult growth of U. lucasi is reduced within the host species representing the more recent host– parasite association. Intraspecific host-induced size differences are inconsistent with the exclusive use of morphometrics to delimit and diagnose species of Uncinaria from pinnipeds