MALARIA PARASITES AND CHLOROQUINE CONCENTRATIONS IN TANZANIAN SCHOOLCHILDREN

Subtherapeutic doses of chloroquine (CQ) are considered to promote dev elopment of Plasmodium falciparum resistance but little is actually kn own about the drug levels in the population in endemic areas. We have therefore measured blood concentrations of CQ in Tanzanian schoolchild ren and related these to parasite microscopy. A total of 163 children (median age 11 years) in a suburb outside Dar es Salaam were followed during four weeks. Thick and thin blood films were obtained once weekl y. Parasites were counted in 200 visual fields. CQ and desethyl-chloro quine (DECQ) were determined with HPLC in 100 mu l of capillary blood. During the study P. falciparum trophozoites were detected in a mean o f 78% of the children, P. falciparum gametocytes in 7.7% and P. malari ae parasites in a mean of 13%. The cumulative prevalence of P. falcipa rum trophozoites and Fl malariae parasites was 96% and 28% respectivel y. On day O and day 28, CQ was found in 78% and 80% of the children an d DECQ in 21% and 31% of them. A total of 19% of all children had a ve rified CQ intake during the study and 35% had probably taken CQ. With a few exceptions (9% had CQ concentrations > 100 nmol/l) drug levels w ere not sufficient to affect parasites with a reduced CQ susceptibilit y but could possibly promote development of resistance by eradicating the most susceptibility part of the parasite population.