Malaria in an urban and a rural area of Zambia.

Children in Lusaka and in a rural area in central Zambia were examined during November 1984 and April 1985 to assess the effect of urbanization on malaria transmission. Of 423 urban children examined in November, 2.4% had scanty parasitaemia, and low titres of malarial antibodies were found in 46%. These proportions increased in April to a parasite rate of 10.3% and malaria antibodies were detected by indirect fluorescent antibody tests (IFAT) in 62%. The presence of malaria antibodies was positively associated with journeys outside the main towns. Examination of paired sera from the 2 periods showed an association between a history of malaria and an increased antibody titre, but failed to show an association between travel outside the main towns and conversion from a negative to a positive IFAT. The spleen rate in children under 15 years old in Lusaka was 3%, indicating hypoendemic malaria. In rural children the parasite rate was 10% and 27% in the 2 seasons, respectively, and over 97% of the children had malaria antibodies. The spleen rate was 20%, indicating mesoendemic malaria. It is concluded that there is only low transmission of malaria in Lusaka so that many people do not develop resistance and are therefore at risk of severe attacks if they do become infected. Possible measures to protect the urban population are discussed.