Host Parasite Interactions in Australian Pinnipeds

<p dir="ltr">Marine mammals are increasingly vulnerable to diverse anthropogenic threats, including infectious disease. This thesis investigated host parasites interactions of the protozoan parasites <i>Cryptosporidium </i>and <i>Giardia </i>across global marine mammal populations. Assessment of the literature for <i>Cryptosporidium </i>and <i>Giardia </i>revealed that these parasites are present in pinnipeds, cetaceans, sirenians, and marine carnivores around the world. <i>Cryptosporidium </i>and <i>Giardia </i>was diverse and included zoonotic species and strains. Experimentally, protozoan parasite prevalence was investigated in 437 faecal DNA samples from three Australian pinniped species using molecular methods. Initial screening with general Eukaryotic primers identified 232 samples (53.1%) as Eukaryote-positive. From these, 162 samples from Australian sea lions (<i>Neophoca cinerea</i>) were selected for further protozoan analysis, based on species, location, and sample year representation. A proportion of these DNA samples were from an ivermectin treatment trial (95 samples) to remove hookworm from the pups, allowing for investigation of ivermectin impact on protozoan pups. Overall parasite prevalence varied (no <i>Cryptosporidium </i>and <i>Giardia </i>and high prevalence of Apicomplexa). No significant difference was observed between parasites prevalence and ivermectin treatment and control samples. These results underscore the need for ongoing surveillance of marine mammal health and improved understanding of host–parasite–environment dynamics for conservation management.</p>