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American trypanosomosis is due to infection with Trypanosoma cruzi (Protozoa, Kinetoplastidae). This is a widespread parasite of small mammals and marsupials throughout most of the Americas, roughly from the Great Lakes of North America (approx. 42 ° N) to southern Argentina (approx. 46 ° S). It is mainly transmitted by blood-sucking bugs of the subfamily Triatominae (Hemiptera, Reduviidae) which are widespread in the Americas, but rare in the Old World. Except in some research laboratories, and infected immigrants from Latin America, T.cruzi has not been reported from the Old World, although closely-related trypanosome species are commonly found in Old and New World bats.Human infection with T.cruzi is generally known as Chagas disease, taking the name of Brasilian clinician Carlos Justiniano das Chagas who first described it from patients in central Brasil (Chagas 1909). Chagas isolated and described the parasite, correctly deduced most of its life-cycle and clinical symptoms associated with the infection, identified the insect vectors and some of the reservoir hosts, and also trialed initial attempts to control it. He was nominated at least twice for the Nobel prize in medicine (Coutinho and Dias 2000; Lewinsohn 2003).Although difficult to treat, Chagas disease can be controlled by measures to halt transmission, primarily by eliminating domestic populations of the insect vectors, together with serological screening to avoid transmission by blood donation from infected donors. Since 1991, a series of multinational initiatives have used this approach to halt transmission over vast regions of the areas previously endemic for the human infection. Estimated prevalence of the human infection has declined from the 1990 estimate of 16–18 million people infected, to the current estimate of just over 7 million infected (OPS 2006; Schofield & Kabayo 2008). Prevalence is expected to decline further, and control strategies are now being adjusted to develop a sustainable system of disease surveillance, focal vector control, and specific treatment for any new cases (Schofield et al. 2006; WHO 2007). Guidance for diagnosis and treatment is also required for non-endemic countries, where recent years have seen increasing migration from Latin America such that cases of chronic Chagas disease have now been reported from amongst Latin American migrants in Europe, USA and Canada, and Japan, together with some congenital cases and transmission from infected blood donors and by organ transplant. |
