The Problem of Parasitic Diseases

Infections caused by parasitic protozoa and helminths cause considerable death, suffering and economic loss in both developing and developed nations. The scale of the problem facing the global community cannot be understated. For example, malaria infection is one of the most prevalent and debilitating diseases in developing countries with 300-500 million clinical cases each year and 1-2 million deaths, mostly in children under 5 years of age. More insidiously, malaria reduces economic growth in Africa alone by 1.3% per annum (p.a.). Parasites also threaten animal productivity and food production. Over 500 million large ruminants are infected with parasitic worms resulting in economic losses of over $3 billion p.a. worldwide. It has recently been estimated that production of meat and milk in S.E. Asia alone will need to grow by 3% p.a. over the next 2 decades to avoid a food crisis by 2020.

In Canada, parasites continue to threaten public health, agriculture, the food chain and the environment, directly impacting on animal productivity and food safety with associated reduction in export potential. With the globalization of world economies and trade, parasitic contamination of imported food is a growing and real concern, as evidenced by 11 outbreaks of cyclosporiasis associated with contaminated fresh produce imported to Canada and the USA from countries such as Guatemala and Peru since 1990. Recent waterborne outbreaks of Giardia, Cryptosporidium and Toxoplasma highlight the important links between livestock parasites, the water supply, the food chain and public health. Contamination of water supplies with Toxoplasma in Victoria (BC) and Cryptosporidium in Saskatchewan have recently caused major public health problems. Exposure to parasites is also increasing as a result of increased international travel and immigration, refugee resettlement, the rise of immunodeficiency diseases and concurrent opportunistic infections, ever increasing development of drug resistance, climate change, and emerging and re-emerging infections: such changes are likely to lead to the emergence of pathogenic diseases not previously seen in Canada (eg. West Nile virus) or the exacerbation of existing diseases. A better understanding of the host-parasite interaction at the molecular level will lead to improved methods for control of these pathogens.

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