Development of resistance by Plasmodium falciparum to sulfadoxine/pyrimethamine in Amhara Region, Northwestern Ethiopia.

Following the high rate of chloroquine-resistant Plasmodium falciparum, Ethiopia changed the national drug policy in 1999 from chloroquine to sulfadoxine/pyrimethamine (SP) as first line. However, the useful therapeutic lifespan of SP may be limited by the rapid emergence of resistance. We conducted a study between October and November 2001 to examine the current extent of SP resistance to P. falciparum in Amhara Region, Northern Ethiopia. A total of 93 patients with uncomplicated P. faliciparum malaria were studied from Habru (n=50) and Weizazirt (n=43) localities. Drug resistance was evaluated using the 14-day WHO in vivo test protocol. Parasitological resistance to SP was found to be 32.0% (16/50) and 4.7% (2/43) in Harbu and Weizazirt localities, respectively. The corresponding clinical failure rates were 20.0% (10/50) and 4.7% (2/43). Of the parasitological failure at Harbu, 9 patients were classified as RI, 6 as RII and one as RIII type response. Among the clinical failures, 7 were LTF while the remaining 3 were ETF. Nevertheless, there was hardly any patient with RII/RIII or ETF response, and only two patients each with RI and LTF response were seen from Weizazirt locality. Therefore, the study underscores the presence of varying level of SP resistance to P. falicparum in the areas studied. Whereas SP remains quite effective in the treatment of uncomplicated P. falciparum in Weizazirt locality, the observed high rate of resistance from Harbu is alarming and an area of concern.