Mwangangi Joseph M, Muturi Ephantus J, Shililu Josephat I, Muriu Simon, Jacob Benjamin, Kabiru Ephantus W, Mbogo Charles M, Githure John I, Novak Robert J
International Centre for Insect Physiology and Ecology, Human Health Division, Nairobi, Kenya.
J Am Mosq Control Assoc. 2007 Dec;23(4):371-7. doi: 10.2987/5605.1.
Water quality of aquatic habitats is an important determinant of female mosquito oviposition and successful larval development. This study examined the influence of environmental covariates on Anopheles arabiensis mosquito abundance in the Mwea Irrigation Scheme, Central Province of Kenya, prior to implementation of a malaria vector control program. Experimental rice plots were used to examine the environmental covariates responsible for regulating abundance and diversity of the aquatic stages of malaria vectors. Mosquito larval sampling and water quality analysis were done weekly from the flooding stage to the rice maturation stage. Sampling for mosquito larvae was conducted using standard dipping technique. During each larval collection, environmental covariates such as pH, temperature, conductivity, salinity, dissolved oxygen, water depth, and rice stage were measured. Anopheles arabiensis larval density was highest between 1 wk before transplanting and 4 wk after transplanting with peaks at weeks 0, 3, and 8. The fluctuation in values of the various environmental covariates showed characteristic patterns in different rice growth phases depending on the changes taking place due to the agronomic practices. Using a backward linear regression model, the factors that were found to be associated with abundance of An. arabiensis larvae at any of the rice growing phases included the following: dissolved oxygen, pH, turbidity, water depth, rice height, number of rice tillers, salinity, conductivity, and temperature. The environmental covariates associated with abundance of An. arabiensis were associated with early vegetative stage of the rice growth. For effective control of developmental stages of mosquito larvae, the application of larvicides should be done at the vegetative stage and the larvicides should persist until the beginning of the reproductive stage of the rice.
水生栖息地的水质是雌性蚊子产卵和幼虫成功发育的重要决定因素。本研究在疟疾媒介控制项目实施之前,考察了肯尼亚中部省姆韦亚灌溉区环境协变量对阿拉伯按蚊数量的影响。利用试验稻田来考察负责调节疟疾媒介水生阶段数量和多样性的环境协变量。从淹水期到水稻成熟期,每周进行蚊虫幼虫采样和水质分析。采用标准舀取技术进行蚊虫幼虫采样。在每次幼虫采集过程中,测量pH值、温度、电导率、盐度、溶解氧、水深和水稻生育期等环境协变量。阿拉伯按蚊幼虫密度在移栽前1周和移栽后4周之间最高,在第0、3和8周达到峰值。各种环境协变量值的波动在不同水稻生长阶段呈现出特征性模式,这取决于农艺措施所导致的变化。使用向后线性回归模型,发现在任何水稻生长阶段与阿拉伯按蚊幼虫数量相关的因素包括以下这些:溶解氧、pH值、浊度、水深、水稻高度、水稻分蘖数、盐度、电导率和温度。与阿拉伯按蚊数量相关的环境协变量与水稻生长的早期营养阶段有关。为有效控制蚊虫幼虫的发育阶段,应在营养阶段施用杀幼虫剂,且杀幼虫剂应持续到水稻生殖阶段开始。