Malaria transmission in Dakar: a two-year survey

Area of Science:

• Medical Entomology
• Tropical Medicine
• Public Health

Background:

• Previous studies indicated low malaria transmission in Dakar's suburbs and minimal evidence in the downtown area.
• However, reports of malaria among residents suggested possible local transmission in urban settings.
• An entomological evaluation was conducted to assess malaria transmission dynamics in two Dakar areas from May 2005 to October 2006.

Purpose of the Study:

• To evaluate malaria transmission in two distinct areas of Dakar, Senegal.
• To identify Anopheles mosquito species and assess their role in malaria transmission.
• To investigate insecticide resistance in local mosquito populations.

Main Methods:

• Human landing collections were used to sample Anopheles mosquitoes in Bel-air and Ouakam areas.
• Mosquitoes were identified using morphological and molecular techniques.
• Plasmodium falciparum circumsporozoite protein (CSP) indexes were measured by ELISA, and entomological inoculation rates (EIR) were calculated. Insecticide resistance was also assessed.

Main Results:

• Anopheles arabiensis was the predominant species (>98%), with Anopheles melas and An. gambiae s.s. detected at lower frequencies.
• Infected mosquitoes were found during the September-November wintering period in both years.
• Annual EIRs ranged from 3 to 9.5 in Bel-air and 3 in Ouakam. Kdr mutation frequency in An. arabiensis was 9-12%.

Conclusions:

• Malaria transmission is confirmed in downtown Dakar, with infected mosquitoes identified in consecutive years.
• The findings align with clinical data showing peak malaria cases between October and December.
• This study marks the first detection of Anopheles melas in Dakar.