# Effect of repeated application of microbial larvicides on malaria transmission in central Côte d'Ivoire

Emile Tchicaya<fnref n="1" />,²*, Benjamin G Koudou<fnref n="1" />,³,⁴, Jürg Utzinger⁵

*From* Parasite to Prevention: Advances in the understanding of malaria
Edinburgh, UK. 20-22 October 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.

**Author details**

¹Centre Suisse de Recherches Scientifques, 01 BP 1303, Abidjan 01, Côte d'Ivoire. ²UFR Biosciences, Université de Cocody-Abidjan, 22 BP 522, Abidjan 22, Côte d'Ivoire. ³Department of Medical Parasitology and Infection Biology, Swiss Tropical Institute, P.O. Box, CH-4002 Basel, Switzerland. ⁴Liverpool School of Tropical Medicine, Liverpool, UK, UFR Sciences de la Nature.

⁵Department of Public Health and Epidemiology, Swiss Tropical Institute, P.O. Box, CH-4002 Basel, Switzerland.

Published: 16 December 2010

doi:10.1186/1475-2875-9-S2-P68

**Cite this article as:** Tchicaya *et al*. Effect of repeated application of microbial larvicides on malaria transmission in central Côte d'Ivoire. *Malaria Journal* 2010 9(Suppl 2):P68.

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<footnote n="1">¹Centre Suisse de Recherches Scientifques, 01 BP 1303, Abidjan 01, Côte d'Ivoire</footnote>