Kissing bugs — vectors of Chagas disease — may be adapting to urban life, say scientists.

CDC's PHIL

[CARACAS] Chagas disease could spread from its rural strongholds into urban areas, scientists have warned, after a surprise outbreak in the Venezuelan capital was found to have local origins.

More than 100 children and staff fell ill at the school in Caracas, and one five-year-old died, as a result of the 2007 outbreak. Doctors diagnosed infection with Trypanosoma cruzi, the parasite which causes Chagas disease.

This is the largest known case of the rare oral transmission of the disease, and the first such event with urban origins, said the study published in The Journal of Infectious Diseases last month (March).

The study traced the source of the outbreak to a jug of guava juice that had been prepared in a suburban home and left uncovered overnight. This allowed the insects that carry the infection — triatomines, usually only found in forested areas, to contaminate the juice.

These insect vectors may now be adapting to semi-urban areas, where expanding cities meet forests, and could become a bigger threat to people through food contamination in the cities, researchers said.

The disease affects around 14 million people worldwide and kills about 15,000 a year. It starts with fever and tiredness and later leads to weakened heart and internal organs.

People usually get infected from faeces dropped in bite wounds from blood-sucking triatomine insects known as 'assassin' or 'kissing' bugs — that live in crevices of poor-quality houses — particularly in rural areas.

Occasional oral transmission from contaminated food and drink has also been reported, but it always had origins in the rural or forested areas where the disease is endemic (see Brazil confirms Chagas outbreak from infected fruit).

Although the control of Chagas vectors has been achieved in some areas, notably in Brazil, Chile and Uruguay, the researchers said that food-borne transmission in the cities may reverse this success.

From now on, any fever with an unknown origin in tropical areas should be considered to be Chagas disease, José Antonio Suarez, one of the authors of the study and a researcher at the Tropical Medicine Institute at the Central University of Venezuela, told SciDev.Net.

Felix Tapia, an immunologist and parasitologist at the Institute of Biomedicine, Central University of Venezuela, who was not involved with the study, said that a change of thinking and strategy to tackle urban Chagas disease is called for as a result of the research.

Link to full article in The Journal of Infectious Diseases

Link to a related editorial in the The Journal of Infectious Diseases