Institut Pierre Richet (IPR), Bouaké, Côte d'Ivoire.
MIVEGEC, IRD, CNRS, Univ. Montpellier, Montpellier, France.
Parasit Vectors. 2019 Mar 27;12(1):146. doi: 10.1186/s13071-019-3404-0.
Although larviciding may be a valuable tool to supplement long-lasting insecticide nets (LLINs) in West Africa in different ecological settings, its actual impact on malaria burden and transmission has yet to be demonstrated. A randomized controlled trial was therefore undertaken to assess the effectiveness of larviciding using Bacillus thuringiensis israeliensis (Bti) in addition to the use of LLINs. In order to optimally implement such a larviciding intervention, we first aimed to identify and to characterize the breeding habitats of Anopheles spp. in the entire study area located in the vicinity of Korhogo in northern Côte d'Ivoire.
We conducted two surveys during the rainy and the dry season, respectively, in the thirty villages around Korhogo involved in the study. In each survey, water bodies located within a 2 km radius around each village were identified and assessed for the presence of mosquito larvae. We morphologically identified the larvae to the genus level and we characterized all of the habitats positive for Anopheles spp. larvae based on a predefined set of criteria.
Overall, 620 and 188 water bodies positive for Anopheles spp. larvae were sampled in the rainy and the dry season, respectively. A broad range of habitat types were identified. Rice paddies accounted for 61% and 57% of the habitats encountered in the rainy and the dry season, respectively. In the rainy season, edges of rivers and streams (12%) were the second most abundant habitats for Anopheles spp. larvae. More than 90% of the Anopheles spp. breeding habitats were surrounded by green areas. Dams, ponds and drains produced higher numbers of Anopheles spp. larvae per square meter than rice paddies (RR = 1.51; 95% CI: 1.18-1.94; P = 0.0010). The density of Anopheles spp. larvae was significantly higher in habitats surrounded by low-density housing (RR = 4.81; 95% CI: 1.84-12.60; P = 0.0014) and green areas (RR = 3.96; 95% CI: 1.92-8.16; P = 0.0002] than habitats surrounded by high-density housing. Turbid water [RR = 1.42 (95% CI: 1.15-1.76; P = 0.0012) was associated with higher densities of Anopheles spp. larvae. The likelihood of finding mosquito pupae in Anopheles spp. breeding habitats was higher in the dry season (OR = 5.92; 95% CI: 2.11-16.63; P = 0.0007) than in the rainy season.
Rice paddies represented the most frequent habitat type for Anopheles spp. larvae in the Korhogo area during both the rainy and the dry seasons. Anopheles spp. breeding habitats covered a very large and dynamic area in the rainy season whereas they were fewer in number in the dry season. In this context, implementing a larviciding strategy from the end of the rainy season to the dry season is presumably the most cost-effective strategy.
尽管在不同的生态环境中，以苏云金芽孢杆菌（Bti）为基础的杀幼虫剂可能是在西非补充长效驱虫蚊帐（LLINs）的一种有价值的工具，但它对疟疾负担和传播的实际影响尚未得到证明。因此，进行了一项随机对照试验，以评估在使用 LLINs 的基础上使用苏云金芽孢杆菌进行杀幼虫的效果。为了优化这种杀幼虫干预措施的实施，我们首先旨在确定和描述位于科特迪瓦北部科霍戈附近研究区域内所有的按蚊滋生地。
我们在雨季和旱季分别在参与研究的 30 个村庄进行了两次调查。在每次调查中，确定了以村庄为中心半径 2 公里范围内的水体，并评估了这些水体中是否存在蚊子幼虫。我们将幼虫形态学鉴定到属的水平，并根据预定义的一套标准对所有存在按蚊幼虫的栖息地进行了特征描述。
总体而言，在雨季和旱季分别有 620 和 188 个水体被发现存在按蚊幼虫。确定了广泛的栖息地类型。稻田在雨季和旱季分别占栖息地的 61%和 57%。在雨季，河流和溪流的边缘（12%）是按蚊幼虫的第二大丰富栖息地。超过 90%的按蚊滋生地周围都有绿色区域。与稻田相比，水坝、池塘和排水沟每平方米产生的按蚊幼虫数量更多（RR=1.51；95%CI：1.18-1.94；P=0.0010）。在房屋密度低（RR=4.81；95%CI：1.84-12.60；P=0.0014）和绿色区域（RR=3.96；95%CI：1.92-8.16；P=0.0002）周围的按蚊幼虫密度显著高于房屋密度高的栖息地。混浊的水（RR=1.42；95%CI：1.15-1.76；P=0.0012）与较高的按蚊幼虫密度相关。在旱季，在按蚊滋生地发现蚊子蛹的可能性（OR=5.92；95%CI：2.11-16.63；P=0.0007）高于雨季。
在雨季和旱季，稻田都是科霍戈地区按蚊幼虫最常见的栖息地类型。在雨季，按蚊滋生地覆盖了一个非常大且动态的区域，而在旱季，按蚊滋生地的数量则较少。在这种情况下，从雨季末到旱季实施杀幼虫策略可能是最具成本效益的策略。
