Malaria transmission risk by the mosquito Anopheles baimaii (formerly known as An. dirus species D) at different hours of the night in North-east India

The risk of acquiring malaria transmitted by Anopheles baimaii Sallum & Peyton, 2005, formerly known as An. dirus species D (Sallum et al., 2005) (Diptera: Culicidae), at different hours of the night in a forest-fringed village of Assam, North-east India was assessed through all-night mosquito landing catches during 1995-2000. An estimated overall mean biting rate of 36.1 bites/person/night (95% CI = 26.2-45.8), a sporozoite rate of 1.9% (95% CI = 1.1-2.9%) and a parous rate of 58.7% (95% CI = 55.3-62.0%) were recorded. Parous and sporozoite-positive females tended to be caught mainly before midnight. The effective entomological inoculation rate was the highest (0.249 positive bites/person/night) from 21.00 to 24.00 hours, suggesting that the second quartile of the night is the most risky period for malaria transmission by An. baimaii. Considering that similar to 21% of mean inoculations take place before 21.00 hours, it appears that there is a need for appropriate protective measures during the pre-bed time period to supplement the impact of insecticide-treated nets against An. baimaii in north-east India.