Prevalence of concomitant infections of plasmodium falciparum and wuchereria bancrofti in mosquito and human populations in Malindi, Kenya
Muturi, Juma Ephantus
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Anopheles gambiae s.l. and An. funestus are important vectors of malaria and lymphatic filariasis, which occur as co-endemic infections along the Kenyan Coast. However, there is no adequate information regarding the occurrence and prevalence of concomitant infections of the two diseases in mosquito and human populations in these areas. This study investigated the prevalence of concomitant infections of Plasmodium falciparum and Wuchereria bancrofti in mosquito and human populations in Jilore and Shakahola villages of Malindi, Kenya. The study was conducted from September 2002 to February 2003. Mosquitoes were sampled inside houses by use of pyrethrum spray sheet collection (PSC) while blood samples were collected by finger prick technique at the end of entomological survey. A total of 2,108 female mosquitoes belonging to 11 species were collected. Anopheles gambiae s.l and An. funestus accounted for 91.03% and 2.85% of all mosquitoes collected respectively, and were the only species harbouring P. falciparum and W. bancrofti infections. Anopheles gambiae s.l contributed most to the transmission and accounted for 100% of P. falciparum and W. bancrofti transmission in Shakahola and 96.7% and 95.0% of P. falciparum and W. bancrofti transmission in Jilore, respectively. The annual entomological inoculation rates (EIR) averaged 122.0 and 109.5 infective bites per person per year in Jilore and Shakahola respectively, the corresponding parasite prevalence being significantly higher in Jilore (36.4%) than in Shakahola (17.4%). The annual transmission potential was 58.4 in Jilore and 11 in Shakahola, while microfilariae prevalence was significantly higher in Jilore (16.0%) than in Shakahola (2.8%). Concomitant infections of P. falciparum sporozoites and filarial worms occurred in 1.15% of An. gambiae s.l but only 0.1% harboured the infective stages of both parasites. None of the persons examined in Shakahola had coinfections of the two parasites, whereas 4.3% of the sample population in Jilore harboured both parasites. These results indicated that the prevalence of malaria and bancroftian filariasis is location specific and that transmission of the two parasites is species specific. The results further indicated that concomitant infections of malaria and filariasis occur but their concurrent transmission is rare. These findings suggest that efforts should be made to integrate the control of malaria and bancroftian filariasis in areas where they co-exist, putting into consideration the local transmission characteristics.