Malaria transmission and insecticide resistance of Anopheles gambiae in Libreville and Port-Gentil, Gabon.
BACKGROUND
Urban malaria is a major health priority for civilian and militaries populations. A preliminary entomologic study has been conducted in 2006-2007, in the French military camps of the two mains towns of Gabon: Libreville and Port-Gentil. The aim was to assess the malaria transmission risk for troops.


METHODS
Mosquitoes sampled by human landing collection were identified morphologically and by molecular methods. The Plasmodium falciparum circumsporozoïte (CSP) indexes were measured by ELISA, and the entomological inoculation rates (EIR) were calculated for both areas. Molecular assessments of pyrethroid knock down (kdr) resistance and of insensitive acetylcholinesterase resistance were conducted.


RESULTS
In Libreville, Anopheles gambiae s.s. S form was the only specie of the An. gambiae complex present and was responsible of 9.4 bites per person per night. The circumsporozoïte index was 0.15% and the entomological inoculation rate estimated to be 1.23 infective bites during the four months period. In Port-Gentil, Anopheles melas (75.5% of catches) and An. gambiae s.s. S form (24.5%) were responsible of 58.7 bites per person per night. The CSP indexes were of 1.67% for An. gambiae s.s and 0.28% for An. melas and the EIRs were respectively of 1.8 infective bites per week and of 0.8 infective bites per week. Both kdr-w and kdr-e mutations in An. gambiae S form were found in Libreville and in Port-Gentil. Insensitive acetylcholinesterase has been detected for the first time in Gabon in Libreville.


CONCLUSIONS
Malaria transmission exists in both town, but with high difference in the level of risk. The co-occurrence of molecular resistances to the main families of insecticide has implications for the effectiveness of the current vector control programmes that are based on pyrethroid-impregnated bed nets.
Département de Parasitologie-mycologie, Faculté de médecine, Université des Sciences de la Santé, B.P. 4009 Libreville, Gabon.
Jean-Romain
JR
Mourou
Thierry
T
Coffinet
Fanny
F
Jarjaval
Bruno
B
Pradines
Rémi
R
Amalvict
Christophe
C
Rogier
Maryvonne
M
Kombila
Frédéric
F
Pagès
D000818:Animals; D000852:Anopheles / Q000187:drug effects* / Q000469:parasitology*; D005260:Female; D005681:Gabon; D006801:Humans; D019476:Insect Proteins / Q000235:genetics; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology; D008288:Malaria / Q000635:transmission*; D058749:Military Facilities; D009154:Mutation; D010963:Plasmodium falciparum / Q000302:isolation & purification*; D011722:Pyrethrins / Q000494:pharmacology; D018570:Risk Assessment
D019476:Insect Proteins; D007306:Insecticides; D011722:Pyrethrins