[The impact of rice fields on malaria transmission in the city of Bouaké, Côte d'Ivoire].

This study evaluates the impact of rice fields in the city of Bouaké on anopheline fauna and malaria transmission. The Anopheles species represents between 11.4 to 39.2% of mosquitoes in the districts with rice fields and 5.2 to 47.8% in lowland districts with market-gardening. An. gambiae constitutes more than 98% of anopheline population in the city. In the lowland districts with market-gardening, biting rates of An. gambiae varied from 3650 to 6935 bites per man per year. Seasonal variations were correlated with rainfall. The mean annual parturity rate was 72% and the mean sporozoitic index 2%. Malaria transmission started at the beginning of the rainy season and attained its height during the second half of this season. Depending on the district, inhabitants were infected with 78 to 134 bites per year. The mean biting rate of An. gambiae in the districts with rice fields varied from 4745 to 22,630 bites per man per year. Seasonal variations were not correlated with rainfall, but with the growth of rice and the two annual cycles of rice cultivation. The parturity rates of the population of An. gambiae were low (46.2% to 57.2%), especially after rice transplantation. The mean infection rates were between 0.7 and 1.0%. The transmission period covered 7 to 11 months depending on the district with two annual peaks observed at the end of rice cultivation. Inhabitants were infected with 44 to 155 bites per year. Rice fields in Bouaké do not seem notably to have modified malaria transmission in the city.