Resistance of Plasmodium falciparum to sulfadoxine-pyrimethamine combination in semi-immune children in Zaria, northern Nigeria

Abstract
The World Health Organization (WHO) extended field test was employed to assess the in vivo sensitivity of Plasmodium falciparum to sulfadoxine-pyrimethamine combination in 44 children in Zaria urban area. 36 children (82%) were fully sensitive to the drug and 8 (18%) were resistant at the RI level. 8 parasite isolates were obtained from the children and successfully cultured in vitro using the WHO microtest (mark II) system. The 8 isolates underwent schizogony at concentrations of 10 000 pmol sulfadoxine/125 pmol pyrimethamine per well, indicating in vitro resistance.