Plasmodium falciparum: susceptibility in vitro and in vivo to chloroquine and sulfadoxine-pyrimethamine in Ghanaian schoolchildren.

In Ghana, resistance of Plasmodium falciparum to chloroquine was observed for the first time in 1986. By the end of 1991 it had reached a high frequency and a substantial degree. A combined study in vivo and in vitro of the response of P. falciparum to chloroquine and sulfadoxine/pyrimethamine was carried out in Madina, Accra, in the coastal area of Ghana, late in 1991. 96 valid tests in vivo were performed with children and adolescents. There were 52 successful tests in vitro with chloroquine, and 52 with sulfadoxine/pyrimethamine. 45% of the chloroquine tests in vivo and 37% of the sulfadoxine/pyrimethamine tests in vivo indicated RII/RIII resistance. Results in vivo and in vitro were significantly correlated. The presence of RIII responses, 9% with chloroquine and 14% with sulfadoxine/pyrimethamine, indicates a need for third-line antimalarial drugs, the unregulated use of which may entail the risk of early and rapid occurrence of multi-resistance.