Dynamics of transmission of Plasmodium falciparum by Anopheles arabiensis and the molecular forms M and S of Anopheles gambiae in Dielmo, Senegal.
BACKGROUND
The adaptation of Anopheles gambiae to humans and its environment involves an ongoing speciation process that can be best demonstrated by the existence of various chromosomal forms adapted to different environments and of two molecular forms known as incipient taxonomic units.


METHODS
The aim of this study was to compare the epidemiologic role of Anopheles arabiens is and the molecular forms M and S of Anopheles gambiae in the transmission of Plasmodium in a rural areas of southern Senegal, Dielmo. The sampling of mosquitoes was carried out monthly between July and December 2004, during the rainy season, by human volunteers and pyrethrum spray catches.


RESULTS
Anopheles arabiensis, An. gambiae M and S forms coexisted during the rainy season with a predominance of the M form in September and the peak of density being observed in August for the S form. Similar parity rates were observed in An. arabiensis [70.9%] (n = 86), An. gambiae M form [68.7%] (n = 64) and An. gambiae S form [81.1%] (n = 156). The circumsporozoite protein (CSP) rates were 2.82% (n = 177), 3.17% (n = 315) and 3.45% (n = 405), with the mean anthropophilic rates being 71.4% (n = 14), 86.3% (n = 22) and 91.6% (n = 24) respectively for An. arabiensis and An. gambiae M and S forms. No significant difference was observed either in host preference or in Plasmodium falciparum infection rates between sympatric M and S populations.


CONCLUSIONS
No difference was observed either in host preference or in Plasmodium falciparum infection rates between sympatric M and S populations, but they present different dynamics of population. These variations are probably attributable to different breeding conditions.
Ndiath
Mamadou Ousmane
MO
Institut de Recherche pour le Développement, Laboratoire de Paludologie et de Zoologie médicale, IRD Hann, BP 1386, Dakar, Sénégal. ndiatt@ird.sn
Brengues
Cécile
C
Konate
Lassana
L
Sokhna
Cheikh
C
Boudin
Christian
C
Trape
Jean François
JF
Fontenille
Didier
D
D000818:Animals; D000852:Anopheles / Q000254:growth & development / Q000378:metabolism / Q000469:parasitology*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007299:Insect Bites and Stings; D007303:Insect Vectors / Q000254:growth & development / Q000378:metabolism / Q000469:parasitology*; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000635:transmission*; D010963:Plasmodium falciparum / Q000502:physiology*; D015800:Protozoan Proteins / Q000378:metabolism; D012675:Senegal / Q000453:epidemiology
D015800:Protozoan Proteins; C041595:circumsporozoite protein, Protozoan