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bioRxiv2019

Anopheles bionomic, insecticide resistance and malaria transmission in southwest Burkina Faso: a pre-intervention study

BackgroundThe present study presents results of entomological surveys conducted to address the malaria vectors bionomic, insecticide resistance and transmission prior to the implementation of new strategies complement long-lasting insecticidal nets (LLINs) in the framework of a randomized control trial in southwest Burkina Faso. MethodsWe conducted entomological surveys in 27 villages during the dry cold season (January 2017), dry hot season (March 2017) and rainy season (June 2017). We carried out hourly catches (from 17:00 to 09:00) inside and outside 4 houses in each village using the Human Landing Catch technique. Mosquitoes were identified using morphological taxonomic keys. Specimens belonging to the Anopheles gambiae complex and Funestus Group were identified using molecular techniques as well as detection of Plasmodium falciparum infection and insecticide resistance target-site mutations. ResultsEight Anopheles species were detected in the area. Anopheles funestus s.s was the main vector during the dry cold season. It was replaced by Anopheles coluzzii during the dry hot season whereas An. coluzzii and An. gambiae s.s. were the dominant species during the rainy season. Species composition of the Anopheles population varied significantly among surveys. All researched target site mutation of insecticide resistance (kdr-w, kdr-e and ace-1) were detected in all members of the An. gambiae complex of the area but at different frequencies. We observed early and late biting phenotypes in the main malaria vector species. Entomological inoculation rates were 0.087, 0.089 and 0.375 infected bites per human per night during dry cold season, dry hot season and rainy season, respectively. ConclusionThe intensity of malaria transmission was high despite the universal coverage with LLINs. We detected early and late biting phenotypes in the main malaria vector species as well as physiological insecticide resistance mechanisms. These vectors might mediate residual transmission. These data highlight the need to develop complementary tools in addition to LLINs in order to better control resistant malaria vectors and to monitor insecticide resistance.

epidemiology↗

bioRxiv2019

Anopheles bionomics, insecticide resistance mechanisms and malaria transmission in the Korhogo area, northern Cote d Ivoire: a pre-intervention study

BackgroundA better understanding of malaria transmission at a local scale is essential for developing and implementing effective control strategies. In the frame of a randomized control trial, we aimed to provide an updated description of malaria transmission in the Korhogo area, northern Cote dIvoire, and to get baseline data for the trial.\n\nMethodsWe performed Human Landing Collections in 26 villages in the Korhogo area during the rainy season (September-October 2016, April-May 2017) and the dry season (November-December 2016, February-March 2017). We used Polymerase chain reaction techniques to ascertain the species of the An. gambiae complex, Plasmodium sp sporozoite infection and insecticide resistance mechanisms in a subset of Anopheles vectors.\n\nResultsAnopheles gambiae s.l. was the predominant malaria vector in the Korhogo area. Overall, more vectors were collected outdoors than indoors (P < 0.001). Of the 774 An. gambiae s.l. tested in the laboratory, 89.65% were An. gambiae s.s. and 10.35% were An. coluzzii. The frequencies of the kdr allele were very high in An. gambiae s.s. but the ace-1 allele was found at moderate frequencies. An unprotected individual living in the Korhogo area received an average of 9.04, 0.63, 0.06 and 0.12 infected bites per night in September-October, November-December, February-March, and April-May, respectively.\n\nConclusionsThe intensity of malaria transmission is extremely high in the Korhogo area, especially during the rainy season. Malaria control in highly endemic areas such as Korhogo needs to be strengthened with complementary tools in order to reduce the burden of the disease.

zoology↗