Susceptibility of Plasmodium falciparum to chloroquine and mefloquine in Somalia.

A field study was conducted in the Malable area, in Somalia, to assess the susceptibility of Plasmodium falciparum to chloroquine and mefloquine. The in vivo response of P. falciparum to standard therapeutic regimen of chloroquine was studied in 16 children (1-12 years) using the standard WHO in vivo field test. All subjects were parasite free by day 3 and no recrudescence occurred during a 7-d follow-up. In the 24 h micro in vitro tests for chloroquine, 29 of 39 tests performed were successful. Of the 29 isolates, 3 showed distinct resistance and 2 were borderline. The drug concentration yielding 99% (EC99) inhibition was 1.64 x 10(-6) M, indicating low grade resistance. For mefloquine, 11 of 20 tests gave interpretable results and were sensitive, although with some heterogeneity. The EC50 and EC99 of 0.24 x 10(-6) M and 1.31 x 10(-6) M respectively indicate sensitivity.