Malaria Transmission in Households in Blantyre, Malawi

Abstract

Although great strides have been made in the reduction of the worldwide burden of malaria disease, a better understanding of the epidemiology of malaria is needed to continue the fight against the disease. Specifically, insight into the transmission of malaria within households might offer new targets of malaria intervention, and policy changes aimed at the control of the spreading antimalarial resistance. To this end, this study examines the relationship between malaria infection and household exposure in Blantyre, Malawi. Blood samples were collected from children and their caregivers for analysis using six neutral, unlinked microsatellite markers. Parasites within infections were genotyped and the infections in children were compared to infections in their caregivers to determine the number of microsatellites shared between the two infections, a marker for the genetic relationship of the two infections. The comparison of genotype between infections, allows a specific infection to be tracked through the human-vector-human transmission cycle. The mean proportion of parasite alleles shared for individuals residing in the same house was compared to that of individuals residing in different households. Overall, children had infections that were more similar to their parents than to that of other caregiver in the population (p value =.036). This indicates that intra-household malaria infections are more similar than inter-household malaria infection and suggests that individuals in the household are a source of malaria infection within the household. For half of the occurrences of shared infections, the parasite was found in both caregiver and child at the same time, a synchronous exposure indicating a shared exposure either within the area or travel outside of the Blantyre area. The results provide encouraging indications that future research may yield new information that will be influential in reducing the burden of malaria disease worldwide through policy decisions regarding parasite control and the prevention of the spread of antimalarial resistance. Further research is needed to assess the intra-household source of infection, and validate the study in other populations.