Malaria attack incidence in a district of Bobo-Dioulasso, Burkina-Faso.

Weekly malaria attack incidence rate has been studied from June to September 1993 in a cluster of children and adults living in a quarter of the city of Bobo-Dioulasso (Burkina Faso). The city is located in the savanna area with an average of I 000 mm rainfall in five months. In this recently built quarter at the outskirts, yearly average malaria transmission was of four infected bites mainly due to Anopheles gambiae. The medical team visited each week each included family (28 families, 290 persons). Malaria attack has been defined as a fever attack or the certitude of fever during the hours before, with clinical malaria-related signs, a patent parasitaemia and the lack of obvious other etiology. Parasitic density threshold of 2 000 PRBC/mm(3) for the children and adolescents, till 16 years old and of 1 000 PRBC/mm(3) for the adults, have been utilized for the definition of unquestionable malaria attack. 4 128 medical observations have been done. 17 unquestionable malaria attacks have been observed in infants, children and adults with parasitic densities from 40 000 to 720 000 PRBC/mm(3) 18 likely attacks were also observed with clinical signs but low density of Plasmodium. All were induced by P. falciparum. From June to the end of July the weekly incidence rate was five for one thousand and from August twelve for one thousand. In a place with a low transmission, the success of an infection is higher than in places with an intense transmission. This observation is of some importance for the control of the disease by reduction of the transmission.