ABSTRACT
Knowledge of the helminth and parasitic arthropod fauna of marine mammals is important to biologists, veterinarians, animal care specialists, managers, and consumers of marine mammals such as indigenous peoples and the public in understanding the significance and role these parasites have in captive and free-ranging marine mammals. Most helminths and parasitic arthropods of marine mammals comprise the normal fauna of otherwise healthy animals and are well adapted to those hosts. Other parasites appear to be new acquisitions in marine mammals, perhaps due to lack of study, and some of these appear to be generally well tolerated. Yet, still other well-known parasites “emerging or resurging” in marine mammals due to habitat degradation, other diseases, immunotoxins, or other stressors (nutritional, environmental, or human-related activities) cause significant disease. Parasitic infections can have direct or indirect effects on health, immune status, survival, recruitment, and population dynamics. Even apparently benign parasites can become opportunistic, invasive, and highly pathogenic in susceptible or weakened animals, particularly in small isolated populations or species at risk. Parasites and the diseases they cause can compromise recruitment, resulting in failure of small threatened populations to recover. Despite our current wealth of parasitological knowledge, new parasites and the diseases they cause are still being documented in marine mammals worldwide. The role of immunotoxins or other stressors in promoting or exacerbating the pathogenicity of parasitic infections is poorly understood in marine mammals, partly due to lack of comparable controls and the involvement of various cofactors (Measures 2001; Jepson et al. 2005; Bull et al. 2006; Kannan et al. 2007; Lair, Measures, and Martineau 2016). Further research, including experimental studies to elucidate life cycles (which are poorly known for parasites in the marine environment), is urgently needed to identify and understand risk factors and threats to the conservation of marine mammals, to inform management decisions, to evaluate health risk to humans from zoonotic parasites, and to determine veterinary treatment if warranted.
