On the other hand, rainfall increased in the interior of western Africa, and the northern limit of the tsetse fly, an insect fatal to cattle, moved south.
另一方面，西非内陆的降雨量增加，采采蝇活动区域的北部边界向南移动——一种对牛致命的昆虫。
2
Tsetse flies are found just in sub-Saharan Africa though only certain species transmit the disease.
采采蝇仅在南撒哈拉非洲存在，但只有某些种类的采采蝇会传播该病。
3
The disease, transmitted mainly by tsetse flies, is prevalent in 37 countries among the poorest of the world.