INCIPIENT RESISTANCE OF PLASMODIUM-FALCIPARUM TO CHLOROQUINE AMONG A SEMI-IMMUNE POPULATION OF THE UNITED-REPUBLIC-OF-TANZANIA .1. RESULTS OF INVIVO AND INVITRO STUDIES AND OF AN OPHTHALMOLOGICAL SURVEY

  • 1 January 1982
    • journal article
    • research article
    • Vol. 60  (1) , 77-87
Abstract
The sensitivity of P. falciparum strains to chloroquine was tested in 1 locality in the north-east of the United Republic of Tanzania, where a chloroquine-medicated salt project was implemented for chemosuppression for many years and where large amounts of the drug have been available during the last decade for the treatment of malaria infections. Single doses of chloroquine (5 or 10 mg of base/kg of body weight) failed to clear P. falciparum trophozoites in asymptomatic parasite carriers selected from the school population. In comparison, clearance had been obtained easily 10 yr previously with 5 mg of base/kg of body weight in several localities in the area. A total dose of 25 mg of base/kg of body weight given over a 3-day period succeeded in clearing asexual parasites from the peripheral blood by day 3 in all instances. Asexual parasites were not found again during the nine days following administration of the drug. All the school children who received 5 or 10 mg of base/kg of body wt at the beginning of the trial were treated with a further 20 mg of base/kg of body wt at the end of the 7-day observation period. Asexual parasites reappeared in the blood of some of these children 7-10 days after the 2nd administration of the drug. Using the vitro microtechnqiue, incomplete schizont inhibition was observed in 3 out of 221 cases at a chloroquine concentration of 1.14 .mu.mol/l of blood. No cases of retinopathy related to the prolonged use of chloroquine were detected among the 221 residents who spent more than 16 consecutive yr in the locality.