| dc.description.abstract | Insecticide-treated bed nets (ITNs) have been shown to significantty reduce malaria transmission in sub-Saharan Africa. Individuals living in areas of high malaria transmission generally harbour multiple parasite strains, which are thought to be responsible for maintaining acquired immunity to malaria. Despite the efficacy of ITNs in reducing bites of infected mosquitoes and parasitaemia, what remains unproven is the impact of ITN on multiple infections of Plasmodium Jalciparum genotypes and the association of multiplicity of infections (MOl) to malaria morbidity indicators. This study used cryopreserved samples collected from children less than 5 years as part a randomized controlled trial of ITNs conducted between October 1996 to February 2001 in Asembo Bay, Rarieda district, western Kenya. Blood samples obtained from 282 malaria-asymptomatic children enrolled at baseline study (BXO) and 5 years after ITN intervention (BX5) had their parasite DNA genotyped. The number of infecting P. Jalciparum genotypes in blood samples was determined by PCR-based genotyping of the merozoite surface proteins 1and 2 (MSP-l and MSP-2). The x2-test and linear regression analysis were used for data analysis. The results indicated extensive polymorphism of P. Jalciparum, except for R033 family of msp-l locus which was poorly polymorphic in .Asembo. There was no significant difference in MOl observed among the children in the ITN and control groups, even 5 years of ITN use. Overall, MOl showed lack of association with malaria morbidity indicators, and an inverse relationship of age with the total number of msp-I and msp-2 genotypes. For msp-2 genotypes, a significant association was shown with auxiliary temperature ~37.5°C (p= 0.021) and parasite . density less than 5,000 parasites/ill (p= 0.014), and specific families such as R033-type of msp-I and FC27-type of msp-2 with parasite density less than 5,000 parasites/ill (p= 0.042 and p= 0.009 respectively). This study found that the use of ITN does not reduce multiplicity of infection and association MOl with malaria morbidity indicators could be strain-specific. This suggests that the use of ITN may not compromise the acquisition of protective immunity in high transmission areas that depend on infections with multiple parasites. | en_US |
