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Effect of repeated application of microbial larvicides on malaria transmission in central Côte d’Ivoire
© Tchicaya et al; licensee BioMed Central Ltd. 2010
Published: 16 December 2010
The effect of repeated application of Bacillus thuringiensis var israeliensis (Bti) and B. sphaericus (Bs) on different entomological parameters and malaria transmission was investigated in a village in central Côte d’Ivoire. First, all potential mosquito breeding sites identified toward the end of the rainy season in a radius of 1.5-km from the village centre were characterized. Next, we applied Bti (0.8 mg/l) and, 3-4 days later, Bs (10 mg/l). The study area was monitored for breeding sites over a 7-month period and microbial larvicides were applied once every 3 wk. Additionally, adult mosquitoes were collected inside and outside human habitations in 4 cross-sectional surveys in 2006 using human landing catches. Repeated application of Bti and Bs showed an effect on Anopheles larvae; in 3 of the last 4 surveys no Anopheles larvae were found, whereas before, 6.5-23.7% of the sites harbored Anopheles larvae. The number of sites positive for Culex larvae decreased after the third treatment round. A total of 2,361 adult mosquitoes were caught in 64 man-night catches; 59.5% of them belonged to the genus of Anopheles, with An. funestus s.l. being the most abundant species. Entomological transmission parameters recorded for 2006 showed a decline in the biting rate of both An. funestus and An. gambiae compared to the preceding year. Moreover, the entomological inoculation rate of An. funestus was significantly reduced (from 328 to 142; P = 0.005) whereas that of An. gambiae remained stable. In conclusion, microbial larvicides might play a role in an integrated approach for malaria control.
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