Control Strategies Against Triatominae

Abstract

Control of Triatominae (Hemiptera, Reduviidae) is a primary component of strategies to halt the transmission of Chagas disease, along with serological screening of blood donors to reduce the likelihood of transmission through infected blood transfusions. In the early 1990s, an estimated 80% of Chagas disease cases were attributed to transmission from triatomine vectors. 1 Since 1991, a series of multinational initiatives have focused on elimination of the domestic vector populations throughout the endemic areas of Latin America. Largely as a result of these initiatives, transmission rates have been steadily reduced, with corresponding reductions in infection prevalence. Current estimates suggest that around 7 million people are infected, down from the 1984 estimate of 24 million 2 ; annual transmission rates are probably fewer than 50,000 new cases per year. 3,4 The geographical distribution of domestic vector populations has been drastically reduced, especially Triatoma infestans in Southern Cone countries and Rhodnius prolixus in Central America. Uruguay, Chile, and Brazil, together with several provinces and departments of Argentina, Bolivia, and Paraguay, have been formally declared free of transmission due to T. infestans. Costa Rica, El Salvador, Honduras, Guatemala, and Nicaragua have recently been declared free of transmission due to R. prolixus and/or its elimination. In addition, there has been steady progress in blood donor screening, with coverage now approaching 100% in most of the endemic countries. But this is not to say that the task of controlling Chagas disease is concluded. Rates of transmission due to domestic vectors remain high in several regions, most notably the Gran Chaco region of Argentina, Bolivia, and Paraguay, as well as parts of the Andean Pact countries and Mexico. Even in those regions where the main domesticvector populations have been eliminated, there is a consistent requirement to maintain surveillance with focal interventions against potential new domestic nfestations.There is not only a risk of repopulation by the main vector species but also a risk of other species invading domestic habitats and either establishing new domestic colonies or provoking accidental transmission (e.g., through contamination of food or drink) without necessarily establishing new colonies. This, in conjunction with declining public health interest in Chagas disease as the apparent control successes become more widely discussed, imposes a need for additional strategies invector surveillance and control that can be sustained as a matter of routine over the long term. Current strategies, based on large-scale campaigns of indoor residual spraying (IRS) against established vector populations, are still required in many areas, but will need to become progressively more focal and guided by a sustainable surveillance system integrated with routine public health vigilance. Such techniques are available, and the strategies are being developed.