Abstract
In February 2010, during the autopsy of a Galapagos sea lion (Zalophus wollebaeki) pup found dead on Santa Fe Island, Galapagos, specimens resembling the hematophagous nematode Uncinaria were found in the small intestine and collected. This parasite has not been reported for the Galapagos sea lion, although it parasitizes several sea lion species in various parts of the world.1,2,3 The hookworms generally damage the enteric mucosa when feeding on the host's blood, causing enteritis and anemia. Uncinarias can also cause severe damage when they penetrate into the peritoneal cavity and can cause high mortality in California sea lion (Z. californianus) and Northern fur seal (Callorhinus ursinus) pups.4,5 The parasites collected from the small intestine of the Galapagos sea lion pup showed morphological and genetic differences to what has previously been described for Uncinaria species isolated from other hosts. Sexual dimorphism of the parasite was very noticeable, the oral capsule showed pronounced buccal plates, and very prominent spicules. Interestingly, the spicules varied in their morphology, some of them showing extensions that resemble spines and others revealing transverse grooves, a phenotype similar to what has been described for Uncinaria spp. Molecular analysis of the ITS ribosomal region showed unique mutations, including transitions, transversions and deletions. A comparative analysis of ITS sequences of different Uncinarias isolated in other pinniped host species showed greater similarity (98%) to the sequence reported for Uncinaria spp. in Z. californianus, suggesting a recent common ancestor of Uncinaria spp. in both the California and the Galapagos sea lions. High phenotypic variation in parasites is to be expected since each host species represents different selective pressures for the parasite, which in turn generates co-evolutionary patterns specific to that pathogen-host system. Investigating nucleotide differences in potential targets for selective pressure, such as pathogenicity of virulence genes, between parasites is a strategy for understanding the complex evolution of Uncinaria and its diversification into different otariid hosts. Therefore, we searched for candidate genes in hematophagous nematodes that have similar pathogenesis in other host species, namely Ancylostoma spp. and Necator americanus. We developed degenerate based parsimonious alignments of conserved regions in the cDNA sequences archived in GenBank. Two genes, specifically related to virulence, were amplified successfully in DNA samples extracted from the Galapagos sea lion Uncinaria specimens, these being macrophage migration inhibitory factor (MMIF) and Necpain (protease), and they yielded products smaller than 1000 bp each, which have now been purified and are being bi-directionally sequenced. A detailed assessment and comparison of Necpain and MMIF sequences in Uncinaria species isolated from different otariid hosts will add valuable information on the evolutionary history of this pathogen and serve as an example of coevolution in pathogens and their mammalian hosts.
* Presenting author
+ Student presenter
Literature Cited
1. Baylis H.A. (1947) A redescription of Uncinaria lucasi Stiles, a hookworm of seals. Parasitology. 38:160–162.
2. Berón-Vera B, Crespo E.A, Raga J.A, Pedraza S.N. (2004) Uncinaria hamiltoni (Nematoda: Ancylostomatidae) in South American sea lions, Otaria flavescens, from Northern Patagonia, Argentina. J Parasitol. 90:860–863.
3. Castinel A, Duignan PJ, Pomroy WE, Lyons ET, Nadler SA, Dailey MD, Wilkinson IS, Chilvers BL. (2006). First report and characterization of adult Uncinaria spp. in New Zealand Sea Lion (Phocarctos hookeri) pups from the Auckland Islands, New Zealand. Parasitol Res. (2006) 98: 304–309.
4. Lyons T, DeLong R, Nadler A, Laake L, Orr J, DeLong L, Pagan C. (2012). Investigations of peritoneal and intestinal infections of adult hookworm (Uncinaria spp.) in northern fur seal (Callorhinus ursinus) and California sea lion (Zalophus californianus) pups on San Miguel Ilad, California (2003). Parasitol Res. (2011) 109:581–589.
5. Spraker T, Delong R, Lyons E, Melin S. 2007. Hookworm enteritis with bacteremia in California sea lion pup on San Miguel Island. Journal of Wildlife Diseases, 43(2), 2007, pp. 179–188.