Tackling malaria hotspots in the Amazon

Tackling malaria hotspots in the Amazon



“For mosquitoes, this is the equivalent of a five-star hotel, ”says Marlon Saavedra, a researcher at Peru’s Universidad Peruana Cayetano Heredia.

Saavedra is referring to the humid swamps found in the northern Amazonian region of Loreto, Peru. He is part of a team led by Dr Dionicia Gamboa that studies factors driving persistent or residual malaria transmission

The research, supported by TDR, the Special Programme for Research and Training in Tropical Diseases, and in collaboration with Peru’s Ministry of Health, aims to better understand this region’s residual malaria burden and its causes and to develop new approaches that can drive down transmission. It is part of a 13-country project spanning Latin America, South-East Asia, Africa and the Western Pacific region.



Loreto region in the Amazon jungle covers almost a third of Peru, and has a population of about 1 million. Here, where rivers serve as highways, humidity is more than 80% with frequent heavy rains and flooding.

Rain and flooding create numerous slow-flowing streams and swamps that encourage mosquitoes to breed. As a result, Loreto's malaria hotspots account for 96% of Peru’s malaria burden.

Photograph: TDR/P. Tsukayama



This swamp in Salvador community, for example, has ideal conditions for mosquito breeding: dark-colored water, Aguaje palm trees that provide nutrients and shade, and proximity to people for blood meals.

Photograph: TDR/P. Tsukayama



“For mosquitoes, this is the equivalent of a five-star hotel"





Dr Dionicia Gamboa of Universidad Peruana Cayetano Heredia, with support from TDR, leads the team that is investigating the factors of residual malaria transmission in four communities in the Mazán district of Loreto – Urco Miraño, Salvador, Libertad and Visto Bueno.

15-metre long barrier screens dipped in insecticide are used to collect mosquitos flying between villages and their habitats for a blood meal, to lay eggs, or to rest. Anopheles darlingi was found to be the most abundant mosquito species in the study sites in Loreto.

Photograph: TDR/P. Tsukayama



Anopheles darlingi is the most abundant mosquito species in Mazán district, Loreto



To map the breeding sites of Anopheles darlingi mosquitoes, the researchers used drones to collect high-resolution images of potential breeding sites, which were then tested for the presence of the mosquitoes.

The use of drones is substantially cheaper than purchasing satellite images, which cannot capture details of small breeding sites, and may be out of date or taken only during the dry season. The resolution of these drone images is 0.1 meter per pixel, higher than that of most satellites. The drones also capture real-time images at low altitude, so cloud cover is not an issue. Proof of concept of this new method to study mosquito breeding sites was published earlier this year.



Images captured by the drones were used to build “orthomosaic” maps – which provide a mosaic of individual pictures – for each of the study sites. Google Earth Engine was used to classify the images, particularly to indicate where mosquitos breed.



The researchers also found that even though bednets are widely used in homes, they don’t provide adequate protection from mosquitoes biting outdoors, where most of the transmission occurs.

Homes with walls made of palm leaves and straw have a higher prevalence of the Plasmodium vivax malaria parasite. Homes near water bodies where mosquitoes breed also have a higher incidence of malaria. This suggests that malaria control strategies should involve the housing sector, according to Dr Gamboa.

TDR-P. Tsukayama 8
TDR/P. Tsukayama
© Credits


TDR-P. Tsukayama 9
TDR/P. Tsukayama
© Credits


Dr Gamboa and her team are collaborating with Peru’s Ministry of Health in developing evidence-based plans and new tools to address persistent malaria transmission.

“Understanding what is happening at the local level is essential to defining solutions tailored to local contexts. This can make all the difference between persistence and elimination,” says Dr Florence Fouque, who is managing this TDR project.

TDR-P. Tsukayama 10
TDR/P. Tsukayama
© Credits


TDR-P. Tsukayama 11
J. Ruiz-Cabrejos
Universidad Peruana Cayetano Heredia
© Credits


TDR is able to conduct this activity thanks to the commitment and support of a variety of donors. Please visit the TDR website for a full list.