Bednets ‘can control spread of Chagas disease’

[LIMA] The use of insecticide-impregnated nets in domestic animal enclosures slows the spread of the vector carrying the parasite that causes Chagas disease, making them a potential tool for controlling the spread of this disease.

These are the findings of research carried out in an urban community in Peru, and published in the October issue of The American Journal of Tropical Medicine and Hygiene.

This is the first time the use of insecticide-treated nets was assessed to prevent infestation of the Chagas disease vector, Triatoma infestans.

"This technique has been shown to be effective in malaria and potentially in the control of leishmaniasis; now we know that it may also be a valuable tool in the control of Chagas disease," says Michael Z. Levy, a postdoctoral fellow from the Fogarty International Center of Maryland, United States.

Levy led a team of Peruvian and US researchers who enclosed guinea pigs in cages with and without insecticide-impregnated nettings to measure the rate of infestation by T. infestans.

Guinea pigs are an important staple for rural and peri-urban Peruvians, but are also a main source of vector infestation. Around 4.8 per cent of schoolchildren in poor communities surrounding the city of Arequipa, where the study was conducted, are affected by Chagas disease.

The researchers found that cages with insecticide-treated nets had almost five times less T. infestans than cages without the nets. The unprotected enclosures were infested at a rate of one bug every two weeks.

They also found that only smaller bug nymphs, which are much less likely to transmit Chagas disease, were able to cross the netting.

"The impregnated nets were especially effective against adult insects. Presumably, the larger insects were less able to fit through or under the mesh," the authors write.

"Nets do not replace insecticide application, which is proven to control Chagas disease vectors, but they may be useful as additional measures where spraying alone does not eliminate the bugs."

"They may be especially useful for wild bugs that visit houses at night and leave, and cannot be controlled through insecticide application," Levy told SciDev.Net.

"These studies were done to see if nets could potentially work to protect people. I think insecticide-impregnated bednets are potentially good interventions against Chagas disease, but we need to do more studies before we recommend that people or control programmes invest in them." 

Link to abstract in The American Journal of Tropical Medicine and Hygiene