Malaria in Afghan refugees in Pakistan.

Prevalence of malaria in Afghan refugees in Pakistan is higher than in the local population. Malaria control officials in Pakistan hypothesized that Afghan refugees have brought a heavy load of malaria infections with them from Afghanistan, causing a serious setback to the malaria control programme in Pakistan. The purpose of this study was to test this hypothesis, because it is important regarding the selection of appropriate strategy for malaria control. The proposed hypothesis is rejected because of the following evidence against it: (i) a comparison of age-specific parasite rates of malaria in Afghan refugees and a nearby local population at Karachi indicated that Afghan refugees were susceptible to malaria even in later age-groups, while infections in the local population were limited to younger age-groups; (ii) a comparison of epidemiological trends of malaria in Afghan refugees and the local population in the North-West Frontier Province from 1979 to 1986 demonstrated that the rate of increase in the prevalence of malaria over the years was much higher in Afghan refugees than in the local population, a manifestation of low herd immunity in Afghan refugees. The most plausible alternate hypothesis is that Afghan refugees, being more susceptible, were at high risk of malaria infection in Pakistan rather than that they brought a high infection load with them from Afghanistan. Therefore, malaria control in Afghan refugee camps in Pakistan should be primarily based on preventive, rather than curative, measures.