Plasmodium falciparum sensitivity to chloroquine in the Buyo Region, Ivory Coast

As part of a project, supported by the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases, for achieving a reduction of mortality due to Plasmodium falciparum by means of a primary health care programme, in vivo and in vitro sensitivity testing of P. falciparum to chloroquine was carried out in the Buyo Region of the Ivory Coast. Blood samples from a total of 595 children aged 2-13 years from 5 villages were screened microscopically and 32 of these children were selected for in vivo testing and 36 for in vitro testing. All 32 in vivo test patients were treated with 25 mg chloroquine base per kg, given in divided doses over 3 days, and all of them completed the 7-day observation period. Daily blood slides were taken and these were negative for asexual parasites on days 3 to 7. The mean parasite clearance time was 1.8 days. The 36 in vitro tests produced satisfactory results in 19 isolates. Complete inhibition was achieved in all 19 at 5.7 pmol chloroquine base per well (1.14 mumol/l of blood); 7 of these isolates showed complete inhibition at 1 pmol, 15 at 2 pmol and 17 at 4 pmol.These results showed that in the population studied there was no evidence of chloroquine resistance in either the in vivo or in vitro tests and they give confirmation of a continued response in West Africa to the standard curative regimen of chloroquine.