New way to screen for chagas disease in children

A new targeted screening strategy could make the diagnosis and treatment of Chagas disease more feasible in low-resource settings, concludes a new study, publishing on December 26, 2007, in the open-access journal PLoS Neglected Tropical Diseases.

Trypanosoma cruzi, the single-cell parasite that causes Chagas disease, is transmitted by triatomine bugs that infest houses in poor communities. The disease, which infects an estimated 11 million people in Latin America, kills more people than any other parasitic disease in the Americas.

Chagas disease control programs have traditionally focused on interrupting the transmission of T. cruzi through vector control measures (such as insecticide spraying), rather than on active case detection and specific treatment of infected people. While control actions have reduced the geographic range and prevalence of major triatomine vectors, without attention to timely diagnosis of those already infected, the window of opportunity for effective treatment (such as giving anti-parasitic drugs) is missed. An important reason for the low rates of treatment is that health services and control programs in Latin America lack sufficient resources for comprehensive blood screening and supervised treatment in the most affected areas.

The study, by Michael Levy (Emory University and the Centers for Disease Control and Prevention, Atlanta, USA, currently at the Fogarty International Center of the NIH) and colleagues, demonstrates an alternative screening strategy that could potentially be much more efficient and cost-effective, and therefore much more viable in the resource-poor regions plagued by the disease.

The researchers performed a serological survey in children 2–18 years old living in a peri-urban community of Arequipa, Peru, where a vector control campaign is currently disrupting transmission of T. cruzi. They found that 5.3% of children had already been infected by the time their households received insecticide application. They also found that households with infected children were significantly clustered spatially around each other.

The researchers then related their findings to data that had been collected during the vector control campaign (entomological, spatial, and census data). They found that using such data to target diagnostic testing would have identified over 83% of the infected children while testing only 22% of eligible children (only 22% would have to be tested because of the way the households with infected children clustered).

Levy and colleagues conclude that data easily collected during an ongoing insecticide spraying campaign in Arequipa could be used to identify children at greatest risk of infection with T. cruzi.

The study is the first, according to the authors, to describe T. cruzi transmission in an urban environment and to show evidence that transmission may be epidemic in Arequipa.

In a related commentary article also publishing on December 26, 2007, in PLoS Neglected Tropical Diseases, Ricardo Gürtler (University of Buenos Aires, Argentina), an internationally recognized authority on Chagas disease, commended Levy and colleagues' study, saying “the usual approaches to active case detection require surveying the whole population at risk, and therefore are labor-intensive and costly. It is in this context that the article by Levy et al. attains high relevance for the pending task of massive case detection and treatment of infected children in resource-poor settings.”

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