Transmission dynamics of malaria in four selected ecological zones of Nigeria in the rainy season

Abstract

Background:Two of the problems of malaria parasite vector control in Nigeria are the diversity of Anopheline vectors and large size of the country. Anopheline distribution and transmission dynamics of malaria were therefore compared between four ecotypes in Nigeria during the rainy season. Methods: Polymerase chain reaction (PCR) was used in molecular identification after morphological identification microscopically. Enzyme linked immunorsorbent assay (ELISA) was used for the blood meal analysis and sporozoite detection. Results: Five species were identified out of 16,410 anophelines collected. An. gambiae s.s made up approximately 29.2%-36.6% of the population in each zone. All five species acted as vectors for P. falciparum. An. gambiae s.s had the highest sporozoite rate. The most infected mosquitoes were found in the rain forest. More blood meals were taken from bovids, except the savannah forest, where 73.3% were on humans and Human Blood index (HBI) was 57.3%. The Entomological inoculation rate (EIR) was a mean of 13.6 ib/p but was highest in the rainforest zone. Conclusions and limitations:This study demonstrates the complex distribution of anophelines and the considerable variations in the intensity of malaria transmission in Nigeria. We highlight the need to consider diverse epidemiological situations when planning countrywide control programmes. Key words: Malaria; vectors; Plasmodium falciparum; transmission dynamics; ecotypes RésuméFond: Deux des problèmes de la commande de vecteur de parasite de malaria au Nigéria sont la diversité des vecteurs d'Anopheline et grande taille du pays. La distribution d'Anopheline et la dynamique de transmission de la malaria ont été donc comparées entre quatre ecotypes au Nigéria pendant la saison des pluies. Méthodes: La réaction en chaîne de polymérase (PCR) a été employée dans l'identification moléculaire après identification morphologique au microscope. L'analyse immunorsorbent liée par enzyme (ELISA) a été employée pour la détection d'analyse et de sporozoite de repas de sang. Résultats: Cinq espèces ont été identifiées sur 16.410 anophelines rassemblés. gambiae s.s composés approximativement 29.2-36.6% de la population dans chaque zone. Chacune des cinq espèces a agi en tant que vecteurs pour P. falciparum. gambiae s.s a eu le taux de sporozoite le plus élevé. Les moustiques les plus infectés ont été trouvés dans la forêt tropicale . Plus de repas de sang ont été pris des bovids, excepté la forêt de la savane, où 73.3% étaient sur des humains et l'index humain de sang (HBI) était 57.3%. Le taux entomologique d'inoculation (EIR) était un moyen de 13.6 ib/p mais était le plus haut dans la zone de forêt tropicale.

Estimation of the Human Blood Index in Malaria Mosquito Vectors in Equatorial Guinea after Indoor Antivector Interventions

“…[27][28][29][30][31] Although some studies report zoophily in Afro-tropical vector populations, [5][6][7] we did not detect such behaviors. This may be because of the scarcity of non-human hosts in collection sites that results from an observed lack of animal husbandry practices in Equatorial Guinea relative to other sub-Saharan African localities.…”

A Simple Key for Identifying the Sibling Species of the Malaria Vector Anopheles gambiae (Giles) Complex by Polytene Chromosome Cytogenetics

“…In a related study, 83.52% P. falciparum sporozoite infection rate was recorded for A. gambiae (Ndiath et al, 2011). The high P. falciparum sporozoite rates shows that the A. gambiae complex members are prominent and potent P. falciparum vectors in South-Western Nigeria and similar report was given by Gilles and Coetzee (1987), Annon (2003), Okwa et al (2007) and Okwa et al (2008). The identified members of the A. gambiae complex, A. gambiae sensu stricto and A. arabiensis, as similarly reported by Okwa et al (2008) and Obembe and Awopetu (2014), are the major P. falciparum vectors in South-Western Nigeria.…”

<span>Sporozoite Infection Rate and Identification of the Infective and Refractory Species of <i>Anopheles gambiae</i> (Giles) Complex</span>

“…Hence, the high P. falciparum sporozoite infection rates for A. gambiae recorded in all the study areas in this study justify the reports from other studies that A. gambiae is highly infective in southwestern Nigeria (Okwa et al, 2007) and it is a prominent malaria vector in Nigeria (Annon, 2003;Gilles and Coetzee, 1987). It has also been reported that A. gambiae is the most prominent malaria vector of P. falciparum, the mosquito species with the highest sporozoite rate and the most infected mosquitoes in the rain forest zone, south-west, of Nigeria (Okwa et al, 2008). The fact that the infective and refractory strains of A. gambiae (sensu stricto) had the same polytene chromosome banding patterns showed that the infective and refractory strains cannot be distinguished using their polytene chromosome banding patterns/photomaps.…”