Chloroquine-resistant Plasmodium falciparum malaria at Nchelenge, northeastern Zambia. Follow-up on 515 hospital patients.

From 1986 until 1988 chloroquine sensitivity of Plasmodium falciparum malaria was monitored in 515 hospital patients in Nchelenge district, northeastern Zambia. After treatment with chloroquine 30 mg base/kg, bloodslides were examined on day 2, 4, 6 and 7. The overall resistance rate was 21.4%, of which 29% was R1-, 30% R2-, 18% R3- and 23% R2-3 resistance. Resistance rates were negatively correlated with age and positively with the initial parasitemia. It is suggested that in vivo tests of chloroquine sensitivity also reflect the host's immune status for malaria. In rural areas with chloroquine resistance in vivo testing should be performed on all malaria patients.