[In vivo chemosensitivity tests of Plasmodium falciparum to chloroquine in Senegal: the development of resistance and the assessment of therapeutic efficacy].

The efficacity of oral chloroquine was assessed in 360 out-clinic patients with symptomatic Plasmodium falciparum malaria who were enrolled at five sites, in four administrative regions of Senegal, between 1991 and 1995. They were three rural areas: Mlomp (Casamance), Bandafassilbel (Eastern Senegal), Diohine (Sine-Saloum) and one urban area: Pikine (agglomeration of Dakar). Parasitological failure at Day-7 was observed in 108 patients (30%) and ranged from 14% to 50% according to the study areas. The proportion of RI, RII and RIII responses were 6%, 23% and 1%, respectively. Chloroquine resistance was lowest in Bandafassi, one of the most remote area of Senegal. It was highest in Mlomp where a malaria control programme with mass chemoprophylaxis had been carried out since 1975. The therapeutic failure rate defined by the persistence or reappearance of fever and P. falciparum trophozoites on days 4-7 was 6%. The percentages of therapeutic failure for RI, RII and RIII patients were respectively 14%, 19% and 100%. These results and those of previous studies in Senegal suggest that chloroquine resistance, which first emerged in vivo in 1988 in Dakar, spread between 1990 and 1993 in all regions of this country. The limitations of in vivo tests for the determination of the therapeutic efficacy of chloroquine in malaria endemic regions with increasing chemoresistance are discussed. The low proportion of potentially severe malaria infections in semi-immune persons, the biases in patients selection, and the possibility of delayed complications, considerably limit the potential of these tests for guiding the choice of the best adapted first line treatment.