# Chagas Disease in Latin America and the United States: Factors Influencing Differences in Transmission Rates Among Differing Populations and Vectors

## TL;DR

Chagas disease is more common in Latin America than in the US, and this paper suggests oral or fecal-oral transmission may explain the difference in infection rates.

## Contribution

The paper argues for wider acceptance of oral or fecal-oral transmission as a key factor in Chagas disease spread.

## Key findings

- Oral Chagas disease is the predominant mode of infection in Brazil.
- Fecal–oral transmission may be a significant risk factor in the US.
- Vectorial transmission is considered improbable and less common than previously assumed.

## Abstract

Chagas disease is rare in the United States and common in Latin America even though both have insect vectors that bite home residents and mammalian reservoirs of the parasite, Trypanosoma cruzi. The commonly accepted mode of vectorial transmission of the parasite is admittedly improbable. Therefore, this paper argues for a wider acceptance of oral or fecal-oral transmission of Chagas disease in both geographic areas. The likely differences in the rates of disease in the two areas are discussed.

Autochthonous Chagas disease remains a health risk for humans in Latin American countries but is rarely found among residents of the United States (US), despite the presence of competent insect vectors and small mammal reservoirs of Trypanosoma cruzi in the lower two-thirds of the US. This report discusses the differences in the rates of autochthonous Chagas disease in Latin America and the US. The key to the differences may lie in the mode (or means) of transmission of parasites to humans. In both Latin America and the US, the so-called vectorial transmission of Chagas disease to humans is the mode of acquisition accepted by most authorities. This mode involves the improbable combination of an infected kissing bug defecating near the mouth or eyes or the site of the bite, followed by the bite victim rubbing infected feces into the wound site or mucous membranes. Outbreaks of Chagas disease due to fecal–oral contamination, known as oral Chagas, have been recorded in Latin America for decades, and at present, oral Chagas is the predominant mode of infection recognized in Brazil. It is perhaps time to consider fecal–oral transmission in its many manifestations as a risk factor for Chagas disease in the US rather than reflexively invoking vectorial transmission. Fecal–oral transmission includes contamination of food and drink by triatomine feces and infection via contaminated fomites and surfaces at home and at worksites, as well as transmission from infected small mammals and other routes discussed in this report.