Retracing micro-epidemics of Chagas disease using epicenter regression

Area of Science:

• Epidemiology
• Infectious Diseases
• Parasitology

Background:

• Vector-borne Chagas disease is an urban issue in Arequipa, Peru, but chronic symptoms are rarely observed.
• This absence of clinical cases has led to speculation about the local Trypanosoma cruzi strain's pathogenicity.

Purpose of the Study:

• To investigate the hypothesis that recent transmission, rather than low pathogenicity, explains the lack of chronic Chagas disease cases in Arequipa.
• To introduce and apply a new method, epicenter regression, for inferring disease transmission history.

Main Methods:

• Developed and applied the 'epicenter regression' method to analyze infection status data.
• Reconstructed the spatial and temporal history of Trypanosoma cruzi transmission in an Arequipa community.

Main Results:

• Transmission occurred as focal micro-epidemics, with the oldest initiating approximately 20 years prior to the study.
• Nearly 5% of the community was infected before vector control measures (insecticide application) in 2004.
• Most infections occurred shortly before the disruption of transmission.

Conclusions:

• The observed absence of chronic Chagas disease symptoms is consistent with a recent history of intense transmission and the disease's long asymptomatic period.
• The findings suggest that the local Trypanosoma cruzi strain may still be pathogenic in the chronic phase, despite the current lack of clinical presentation.