ABSTRACT
Several factors can determine the outcome of a malarial infection. Studies on susceptibility or resistance to malarial infection can be confounded by differences in transmission. In the present study, the relationship between vector abundance and Plasmodium falciparum infection rate of Gabonese children was studied. Indoor human bait catches were conducted in the houses of two groups of children, those who had been found earlier to be either frequently (> 3 infections per year) or rarely (< 0.5 infections per year) infected with P. falciparum. The human biting rate was 12 and 31 bites per person per night during the dry and the rainy season, with 3% and 16% Anopheles, respectively. Anopheles gambiae and A. moucheti were found to be the only vectors involved in the transmission of malaria in this area. No significant difference in the abundance and the rate of P. falciparum infection of the Anopheles mosquitoes was found among children rarely or frequently infected. Differences in transmission cannot account for differences in infection rates in our study group. Hereditary and immunological factors seem to be the primary determinants for the outcome of malarial infection.
Subject(s)
Anopheles/parasitology , Insect Bites and Stings , Insect Vectors/parasitology , Malaria, Falciparum/transmission , Plasmodium falciparum/isolation & purification , Animals , Anopheles/classification , Child , Child, Preschool , DNA Primers/chemistry , DNA, Protozoan/analysis , Disease Vectors , Gabon/epidemiology , Humans , Insect Vectors/physiology , Malaria, Falciparum/epidemiology , Plasmodium falciparum/genetics , Polymerase Chain Reaction , SeasonsABSTRACT
Mosquitoes were collected during 3 separate periods in 3 areas of different malaria transmission rates in the province of Moyen Ogooué, Gabon, within 1 year (July 1996-May 1997). The campus of the Albert Schweitzer Hospital (HAS) and 2 villages, Bellevue and Tchad, were investigated. A total of 19,836 specimens were collected: 13,122 Mansonia, 3944 Anopheles, 2755 Culex and 15 Aedes were captured. The number of mosquitoes was 7896 and 7995 in July to August and from April to May respectively, and dropped to approximately half in November to December. The individual species showed a different distribution pattern in the 3 study areas. In Tchad we found the lowest number of mosquitoes and also the fewest Anopheles, but when we investigated the number of Plasmodium falciparum-infected Anopheles sp. we observed the highest entomological inoculation rate (EIR) there. The EIRs were 23 in HAS, 53 in Bellevue and 61 in Tchad. The method used to determine the number of infected mosquitoes was an enzyme-linked immunosorbent assay (ELISA), confirmed by a polymerase chain reaction-based approach. The ELISA alone revealed too many false-positive mosquitoes.
