Piracicaba’s Epidemiologic Surveillance service released new data this week which showed a 91% reduction of dengue fever cases registered in the CECAP/Eldorado district, an area of 5,000 residents, in the 2015/2016 dengue-year as compared to the 2014/2015 period.

The incidence decreased to just 12 cases in 2015/2016, the first year in which Friendly Aedes, the genetically engineered mosquitoes that fight wild Aedes aegypti, were released there, versus 133 cases in the previous year. According to Epidemiologic Surveillance the rest of the municipality saw a 52% reduction in dengue fever incidence during the same period, from 3,487 cases in the 2014/2015 period to 1,676 cases in 2015/2016.

Additionally, the overall incidence rate in CECAP/Eldorado for the dengue-year 2014/2015 was 195% larger than the rate recorded for the rest of the municipality. In the dengue-year 2015/2016, the rate in CECAP/Eldorado was 45% lower than the rate in the rest of the municipality. The latest data roundup also reports zero cases of Zika and chikungunya in CECAP/Eldorado.

“Over the course of one year, we were able to bring the dengue fever incidence down by more than 50% in Piracicaba — the outcome of diligent work to eliminate still water spots, the breeding site of the mosquito,” says the city’s Secretary of Health,Pedro Mello. “In CECAP/Eldorado, where we had the Friendly Aedes project, the reduction was extraordinary, going over 90%.”

“We are delighted with the result achieved so far by Friendly Aedes which shows the potential of our approach. We hope to see this effect on a larger scale beyond the limited area of CECAP/Eldorado with our expansion into Piracicaba’s downtown city,” says Glen Slade, Oxitec do Brasil director.

Oxitec has been working in Aedes aegypti control for more than a decade. It is a pioneer in the use of a biological method to suppress wild populations of this dangerous mosquito species through the release of Friendly Aedes males, which don’t bite and don’t transmit disease. When released, these males search for wild females to mate, and their offspring inherit a self-limiting gene that makes them die before reaching functional adulthood.

Aedes aegypti Image/CDC
Aedes aegypti
Image/CDC