Abstract
Background: Malaria remains a major public health problem in Cameroon; however, despite reports on the adaptation of anopheline species to urban habitats, there is still not enough information on malaria transmission pattern in urban settings. In the frame of a larval control trial in the city of Yaoundé, we conducted baseline surveys to assess malaria transmission dynamics in this city. Methods: Adult mosquitoes were collected indoors and outdoors using CDC light traps and human landing catches from March 2017 to March 2018 in 30 districts of Yaoundé, Cameroon. Mosquitoes were sorted by genus and identified to the species level using PCR. The TaqMan method and ELISA were used to determine mosquito infection status to Plasmodium. Bioassays were conducted to assess female Anopheles gambiae susceptibility to insecticides. Results: A total of 218,991 mosquitoes were collected. The main malaria vectors were An. gambiae s.l. (n=6154) and An. funestus s.l. (n=229). Of the 1476 An. gambiae s.l. processed by PCR, 92.19% were An. coluzzii and 7.81% An. gambiae. An. funestus s.l. was composed of 93.01% (173/186) An. funestus and 4.84% (13/186) An. leesoni. The average biting rate of anopheline was significantly high outdoor than indoor (P=0.013). Seasonal variation in mosquito abundance and biting rate was recorded. The infection rate by Plasmodium falciparum was 2.13% (104/4893 mosquitoes processed). The annual entomological inoculation rate was found to vary from 0 to 92 infective bites/man/year (ib/m/y). Malaria transmission risk was high outdoor (66.65 ib/m/y) compared to indoor (31.14 ib/m/y). An. gambiae s.l. was found highly resistant to DDT, permethrin and deltamethrin. High prevalence of the West Africa kdr allele 1014F was recorded and this was not found to influence An. gambiae s.l. infection status. Conclusion: The study suggests high malaria transmission occurring in the city of Yaoundé and call for immediate actions to improve control strategies.
Highlights
The world population has registered unprecedented growth during the last decades with Africa and Asia displaying the most important rates[1]
Yaoundé is situated in the equatorial forest domain, the extension of settlements has significantly reduced the forest cover which is restricted to the nearby rural area
High and permanent malaria transmission was recorded in the city of Yaoundé and was consistent with studies conducted so far suggesting urban malaria as a public health threat in most sub-Saharan Africa cities[1,6,37,38,39]
Summary
The world population has registered unprecedented growth during the last decades with Africa and Asia displaying the most important rates[1]. In Cameroon the population is estimated at 25 million inhabitants and over 1⁄4 of this population is considered to live in the two main cities of the country, Yaoundé and Douala[8]. The capital city of Cameroon has seen its population multiplied by 6 over the two last decades and has a population estimated at about 3 million inhabitants[8]. At 30 years after interruption of these campaigns, very limited transmission level was still recorded in the city centre. Contrasting pattern was, recorded at the city periphery or nearby rural settings where transmission levels varying from 277 to 350 infected bites per man per year were recorded[14,15,16]
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