Susceptibility of Plasmodium falciparum to chloroquine and mefloquine in Ouagadougou area (Burkina Faso).

Plasmodium falciparum susceptibility to chloroquine in vivo and to chloroquine and mefloquine in vitro was investigated in children living in Ouagadougou area (Burkina Faso) in October 1991. The 7-day WHO in vivo field test was used, with follow-up on days 2, 4, 7 after treatment with 25 mg base of chloroquine per kg body weight given over 3 days, on children aged 2-8 years with monospecific P. falciparum infection (parasite density higher than 800 asexual parasites/microliters of blood), and negative Bergqvist urine tests. At the same time, the in vitro response was assessed using WHO standard test kits. Chloroquine treatment in vivo resulted in parasite clearance in 47 subjects (92.2%) within 7 days (S/RI responses). Parasitaemia did not clear in 4 cases (7.8% of RII responses). There were no RIII responses. The sensitivity study in vitro showed a low degree of chloroquine resistance in 2 out of 12 isolates tested and a mean 50% effective dose (EC50) and EC99 of 0.12 mumol and 1.47 mumol/litre of blood, respectively. All isolates tested were inhibited by mefloquine at 1.6 mumol/litre of blood, indicating full sensitivity. The present study demonstrates that first-line treatment with chloroquine is still satisfactorily effective in the study area of Burkina Faso.