Modeling Household Transmission of American Trypanosomiasis

Abstract

American trypanosomiasis, or Chagas disease, caused by the protozoan parasite Trypanosoma cruzi and transmitted by blood-feeding triatomine bugs, is a chronic, frequently fatal infection that is common in Latin America. Neither adequate drugs nor a vaccine is available. A mathematical model calibrated to detailed household data from three villages in northwest Argentina shows that householders could greatly reduce the risk of human infection by excluding domestic animals, especially infected dogs, from bedrooms; removing potential refuges for bugs from walls and ceilings; and using domestically applied insecticides. Low-cost, locally practicable environmental management combined with intermittent use of insecticides can sustainably control transmission of T. cruzi to humans in rural Argentina and probably elsewhere. Chagas disease, or American trypanosomiasis, is endemic in Central and South America. An estimated 16 to 18 million persons are infected with Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae), the causative agent of Chagas disease, and 100 million people (roughly one-quarter of the population) are at risk of infection (1). Despite decreasing rates of prevalence and incidence of T. cruzi infection (2, 3), Chagas disease remains a serious obstacle to health and economic development in Latin America, especially for the rural poor. The repertoire of control measures is limited. Two drugs are curative in the acute and early chronic phase of infection but have adverse effects and may not always eliminate T. cruzi. No vaccines are available to prevent infection. Transmission may be interrupted by residual spraying to kill blood-feeding triatomine bugs (the vector of T. cruzi), screening blood donors, and treating infected infants born to infected mothers. A more controversial strategy for interrupting transmission is to divert bugs from humans by the use of animals that are not susceptible to T. cruzi (4). This strategy, called zooprophylaxis, is controversial for other vector-borne diseases (5) as well and may remain so for T. cruzi because it cannot be tested experimentally. Ethical considerations bar a randomized prospective field study in which the human prevalence of T. cruzi infection is compared between households that do, and those that do not, keep domestic animals in bedroom areas in the presence of domestic triatomine infestations.

Molecular epidemiology of domestic and sylvatic Trypanosoma cruzi infection in rural northwestern Argentina

“…Based on molecular evidence, this result lends further support to the importance of dogs and cats as domestic reservoir hosts of T. cruzi given their high infectivity and frequent contact with domestic bugs (Cardinal et al, 2007;Gürtler et al, 2007a, b). Households harboring infected dogs or cats were observed and predicted to be at greater risk of transmission (Cohen and Gürtler, 2001;Gürtler et al, 2005), but molecular evidence of the links between bugs and host species at the household level were lacking. In a similar study in Chaco province, different lineages were found infecting dogs and humans (Diosque et al, 2003).…”

“…The household is where the domestic transmission of T. cruzi by Tr. infestans is most intense (Cohen and Gürtler, 2001). Here we provide molecular evidence showing that human habitations may also be a source of TC IIe-infected bugs dispersing by flight toward peridomestic sites and beyond .…”

Soroprevalência da infecção por Trypanosoma cruzi em cães de uma área rural do Estado de Mato Grosso do Sul

“…Os cães são considerados importantes reservatórios de T. cruzi e têm um relevante papel na manutenção e interação entre o ciclo doméstico e silvestre da doença (Montenegro et al 2002, Crisante et al 2006. Portanto, considerando que o estudo nessa espécie é importante para determinar a presença do tripanosomatideo e o risco de seres humanos contraírem a doença (Cohen & Gürtler 2001, Reithinger et al 2005, objetivou-se avaliar a reatividade de anticorpos anti-Trypanosoma cruzi em cães de uma área rural no Mato Grosso do Sul, onde casos humanos autóctones da doença de Chagas foram previamente relatados (Borges-Pereira et al 2001, Pompilio et al 2005 Chagas disease is an anthropozoonosis caused by Trypanosoma cruzi and dogs are considered to be one of the main reservoirs of the disease in the South America. This study evaluates the occurrence of the infection caused by T. cruzi in dogs from a rural area of Mato Grosso do Sul, Brazil.…”

A logistic delay differential equation model for Chagas disease with interrupted spraying schedules

“…Information on the pertinent biological processes can be found in [8]. The full details of the model assumptions can be found in [21].…”