Spatial Clustering of Chagas Disease Helps Screening in Peru

A new targeted-screening strategy could make the diagnosis and treatment of Chagas disease more feasible in low-resource settings. The strategy is based on a study that found that households with infected children were significantly clustered spatially around each other.

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.

A new study has demonstrated an alternative screening strategy that could potentially be much more efficient, cost-effective, and viable in the resource-poor regions plagued by the disease.

Michael Levy of Emory University (Atlanta, GA, USA), the Centers for Disease Control and Prevention, (CDC; Atlanta, GA, USA), currently at the Fogarty International Center of the National Institutes of Health (NIH; Bethesda, MD, USA), and colleagues 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 findings were related to data that had been collected during a vector control campaign that included 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).

An important reason for the low rates of treatment in Latin America is that health services and control programs lack sufficient resources for comprehensive blood screening and supervised treatment in the most affected areas. Michael Levy's study showed that that data easily collected during an ongoing insecticide spraying campaign in an urban area could be used to identify children at greatest risk of infection with T. cruzi.


Related Links:
Centers for Disease Control and Prevention
Emory University
Fogarty International Center of the National Institutes of Health