Date Published: December 26, 2007
Publisher: Public Library of Science
Author(s): Michael Z. Levy, Vivian Kawai, Natalie M. Bowman, Lance A. Waller, Lilia Cabrera, Viviana V. Pinedo-Cancino, Amy E. Seitz, Frank J. Steurer, Juan G. Cornejo del Carpio, Eleazar Cordova-Benzaquen, James H. Maguire, Robert H. Gilman, Caryn Bern, Ricardo Gurtler
Abstract: BackgroundMillions of people are infected with Trypanosoma cruzi, the causative agent of Chagas disease in Latin America. Anti-trypanosomal drug therapy can cure infected individuals, but treatment efficacy is highest early in infection. Vector control campaigns disrupt transmission of T. cruzi, but without timely diagnosis, children infected prior to vector control often miss the window of opportunity for effective chemotherapy.Methods and FindingsWe performed a serological survey in children 2–18 years old living in a peri-urban community of Arequipa, Peru, and linked the results to entomologic, spatial and census data gathered during a vector control campaign. 23 of 433 (5.3% [95% CI 3.4–7.9]) children were confirmed seropositive for T. cruzi infection by two methods. Spatial analysis revealed that households with infected children were very tightly clustered within looser clusters of households with parasite-infected vectors. Bayesian hierarchical mixed models, which controlled for clustering of infection, showed that a child’s risk of being seropositive increased by 20% per year of age and 4% per vector captured within the child’s house. Receiver operator characteristic (ROC) plots of best-fit models suggest that more than 83% of infected children could be identified while testing only 22% of eligible children.ConclusionsWe found evidence of spatially-focal vector-borne T. cruzi transmission in peri-urban Arequipa. Ongoing vector control campaigns, in addition to preventing further parasite transmission, facilitate the collection of data essential to identifying children at high risk of T. cruzi infection. Targeted screening strategies could make integration of diagnosis and treatment of children into Chagas disease control programs feasible in lower-resource settings.
Partial Text: An estimated 11 million people are currently infected with the causative agent of Chagas disease, Trypanosoma cruzi, in Latin America ,. T. cruzi is a protozoan parasite carried in the gut of bloodsucking triatomine bugs (Hemiptera, Reduviidae), and humans become infected with the trypanosome mainly through contamination with the insect’s feces deposited on mucous membranes or broken skin. Many countries have implemented Chagas disease control activities, though most focus on interruption of T. cruzi transmission rather than surveillance for infection among human populations at risk. Triatoma infestans is the principal vector of T. cruzi in South America and the sole vector in southern Peru. A campaign to eliminate T. infestans, known as the Southern Cone Initiative, has been remarkably successful in interrupting vector-borne transmission of T. cruzi through household insecticide application, especially in Uruguay, Chile and Brazil . Although the World Health Organization recommends serologic diagnosis and drug treatment of all T. cruzi-infected children in affected areas, national control programs in Peru and other countries have not had sufficient resources for comprehensive serological screening .
Specimens were tested for a total of 433 children. Of these, 26 (6.0% [95% CI 3.8–8.4]) were positive for antibodies to T. cruzi by ELISA, and 23 (5.3% [95% CI 3.4–7.9]) were confirmed positive by IFA. No ELISA-negative specimens were positive by IFA. ELISA-positive specimens from 3 children were IFA negative; these children were excluded from subsequent analysis. Thirty-two children either lived in households that refused spraying or could not be matched to households based on address information provided by their schools. The total sample size for risk factor analyses was 398 children, of whom 23 (5.8%) were confirmed seropositive for T. cruzi infection.
Chagas disease transmission cycles have become established in communities on the outskirts of the city of Arequipa, Peru. A vector control campaign is currently disrupting transmission of T. cruzi, but we found 5.3% of children in Guadalupe had already been infected by the time their households received insecticide application. Many thousands of children live in similar communities in Arequipa and likely represent a significant proportion of the Chagas disease burden in Peru.