Water with an excess of ammonia (NH3) attracts the pregnant female Aedes aegypti mosquito, which transmits dengue, according to a study by the epidemic control agency of the Brazilian state of São Paulo. Water with an excess of ammonia (NH3) attracts the pregnant female Aedes aegypti mosquito, which transmits dengue, according to a study by the epidemic control agency of the Brazilian state of São Paulo.

Nitrogen, which can come from natural soil processes or from pollutant materials, “makes organic material proliferate, which feeds the larvae,” Gisela Marques, coordinator of the study, told Tierramérica.

The researchers observed that in Potim, a town of 20,000 people, the presence of the mosquitoes persisted in 19.2 percent of the homes in late 2009, despite years of fighting these insects, unlike other towns.

The infested houses use water from a deep central well. Analysis of the water found 1.93 milligrams of nitrogen per liter – higher than the 1.5 milligrams considered the maximum allowed. In the laboratory, the female Aedes aegypti produced 3.6 times more eggs in that water than in the water from the neighboring city of Taubaté.