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Giardia and Cryptosporidium in pinnipeds from the Gulf of St. Lawrence, Canada

Appelbee, Amber (2006) Giardia and Cryptosporidium in pinnipeds from the Gulf of St. Lawrence, Canada. PhD thesis, Murdoch University.

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Giardia and Cryptosporidium are protozoan parasites known to cause enteric disease in terrestrial mammals, reptiles and birds. Compared to the abundance of surveys that have examined Giardia and Cryptosporidium in terrestrial wildlife species, very few studies on either parasite have been undertaken on marine mammal species. Studies of shellfish, marine waters and water treatment plants clearly indicate that marine ecosystems are contaminated with Giardia and Cryptosporidium. In spite of these data the extent to which these parasites extend into the marine environment and how they may impact on marine mammal health remains largely unknown. The aim of this thesis was to expand our current knowledge of Giardia and Cryptosporidium in the marine environment and in particular, the harp and hooded seal populations of the Gulf of St. Lawrence, Canada.

A large-scale serological survey of a large cohort of serum samples clearly show that, as is the case with terrestrial mammals, Giardia is ubiquitous in the marine environment. Sera positive for G. duodenalis-specific IgG were detected in almost all cetacean and pinniped species examined, and from all regions of the St. Lawrence estuary, Gulf of St. Lawrence and from the Canadian arctic.

In the case of harp and hooded seals, they are actively infected with Assemblage A, a zoonotic strain of G. duodenalis and represent a previously unrecognised contributor to the overall environmental parasite burden. The discovery of this variant of Giardia in a phocid host, along with their susceptibility to infection with terrestrial strains of both Giardia and Cryptosporidium, highlight the potential zoonotic transmission from seals to humans through the consumption of uncooked intestines and general animal handling during research or hunting practices. The identification of this zoonotic strain of Giardia in seals also demonstrates the potential for anthropogenic activities such as human sewage treatment and agriculture runoff to be a significant source of contamination for marine mammals.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary and Biomedical Sciences
Supervisor(s): Thompson, Andrew
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