Munga Stephen, Minakawa Noboru, Zhou Guofa, Mushinzimana Emmanuel, Barrack Okeyo-Owuor J, Githeko Andrew K, Yan Guiyun
Kenya Medical Research Institute, Kisumu, Kenya.
Am J Trop Med Hyg. 2006 Jan;74(1):69-75.
We examined the effects of land cover type on survivorship and productivity of Anopheles gambiae in Kakamega in the western Kenyan highlands (elevation = 1,420-1,580 meters above sea level). Under natural conditions, An. gambiae sensu lato adults emerged only from farmland habitats, with an estimated productivity of 1.82 mosquitoes/meter(2)/week, but not from forest and swamp habitats. To determine the effects of intraspecific competition and land cover types, semi-natural larval habitats were created within three land cover types (farmland, forest, and natural swamp), and three different densities of An. gambiae sensu stricto larvae were introduced to the larval habitats. The mosquito pupation rate in farmland habitats was significantly greater than in swamp and forest habitats, and larval-to-pupal development times were significantly shorter. At higher densities, the larvae responded to increased intraspecific competition by extending their development time and emerging as smaller adults, but initial larval density showed no significant effects on pupation rate. Land cover type may affect larval survivorship and adult productivity through its effects on water temperature and nutrients in the aquatic habitats, as shown by the significantly higher water temperature in farmland habitats, enhanced pupation rates and shortened development times from the addition of food to habitats, and a significant negative correlation of the occurrence of An. gambiae larvae with canopy cover and emergent plants in natural habitats. These results suggest that deforestation and cultivation of natural swamps in the western Kenyan highland create conditions favorable for the survival of An. gambiae larvae, and consequently increase the risks of malaria transmission to the human population.
我们研究了肯尼亚西部高地卡卡梅加地区（海拔1420 - 1580米）土地覆盖类型对冈比亚按蚊生存和繁殖力的影响。在自然条件下，冈比亚按蚊广义成虫仅从农田栖息地羽化，估计繁殖力为1.82只蚊子/平方米/周，而森林和沼泽栖息地则没有。为了确定种内竞争和土地覆盖类型的影响，在三种土地覆盖类型（农田、森林和天然沼泽）内创建了半自然幼虫栖息地，并向幼虫栖息地引入了三种不同密度的冈比亚按蚊狭义幼虫。农田栖息地的蚊子化蛹率显著高于沼泽和森林栖息地，幼虫到蛹的发育时间显著更短。在较高密度下，幼虫通过延长发育时间并羽化出较小的成虫来应对种内竞争的增加，但初始幼虫密度对化蛹率没有显著影响。土地覆盖类型可能通过影响水生栖息地的水温及养分来影响幼虫的生存和成虫的繁殖力，农田栖息地水温显著更高、栖息地添加食物后化蛹率提高且发育时间缩短，以及天然栖息地中冈比亚按蚊幼虫的出现与树冠覆盖和挺水植物显著负相关均表明了这一点。这些结果表明，肯尼亚西部高地的森林砍伐和天然沼泽的开垦为冈比亚按蚊幼虫的生存创造了有利条件，从而增加了向人类传播疟疾的风险。
