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Technical Thematic Report No. 7. - Wildlife pathogens and diseases in Canada

Integrated Summary

Disease occurrence patterns in Canadian wild vertebrates in the past two decades appear to conform to the general global pattern of dynamic change and progressive emergence of disease (Jones et al., 2008). At least 14 of the 27 pathogens discussed in this report cause diseases in Canadian wildlife that fit the definition of emerging diseases. Seven pathogens – the raccoon strain of rabies virus, West Nile virus, the house finch variant of Mycoplasma gallisepticum, chronic wasting disease prion, adenovirus of deer, and the Great Lakes variant of viral hemorrhagic septicemia – are new to Canada and appeared during the preceding two decades. Seven others – Newcastle disease virus, Pasteurella multocida (avian cholera), Lyme disease, bovine tuberculosis, chytrid fungus, type-E botulism and Elaphostrongylus rangiferi – have changed their patterns of occurrence significantly during the same period. There are plausible explanations for the emergence of some of these diseases: for example, type-E botulism occurring in association with invasive species causing radical change in the ecology of the Great Lakes; the range of Lyme disease expanding as a function of climate warming and its effect on the tick vector; the introduction of West Nile virus to North America in 1999 and of CWD prion to Canada in the 1980s. For others, the factors responsible for the evident changes in patterns of occurrence have not been identified and may be both multiple and complex (Plowright et al., 2008). The unprecedented scale and speed of environmental change which has characterized the 20th century is likely to be maintained or accelerated in the 21st century (McNeill, 2000; Diamond, 2005). Disease emergence and changing patterns of disease occurrence in Canada’s wild vertebrates are likely to continue and perhaps intensify in the coming decades in response to these intense environmental variables and their effects on the interactions among animals and their pathogens.