Entomological and parasitological parameters of malaria transmission in Douguia, Chad.

Malaria remains a threat for many countries, especially in Chad where it is the leading cause of morbidity and mortality. Few reliable data exist, however, about the entomological and parasitological parameters of malaria transmission. The objective of this study was to investigate the entomological and parasitological parameters of malaria transmission in Douguia, a village located 75 km northeast of Ndjamena (Chad), as part of a training program for participants in Chad's malaria control program. Mosquitoes were collected after morning pyrethroid spraying, with a mouth aspirator. The parasitological data were collected by a rapid diagnosis test or microscopic examination. The study examined 350 subjects aged from 6 months to 80 years. The plasmodic index (PI) of Plasmodium falciparum was 25.4 % (n = 89) and the gametocygenic index (GI) 9.1 % (n = 32); they varied significantly from one age group to another (p = 10- 3). The PI in pregnant women attending antenatal clinics was 18.7 % (n = 12/64). Three Anopheles species were found: Anopheles gambiae s.l, An. arabiensis and An. pharoensis. An. coluzzii accounted for 94.9 % of the An. gambiae s.s. The antigen sporozoite index (SI) was 4.5 %. Our results confirm the endemicity of malaria in Chad (Douguia) and underline the major role of An. gambiae s.l. in its transmission. However, repeated studies using PCR for Plasmodium detection would help to improve our understanding of its epidemiology.