填空题 Across Africa, the tsetse fly threatens a staggering 55 millions people and their 1livestock. The insect sucks blood and in doing so may pass on babies or the dead 2parasite that causes trypanosomiasis, sometimes it known as sleeping sickness. 3Infected animals suffer of poor growth, weight loss and low milk yield. They 4may also become fertile and die. An estimated 5000,000 people are also affected 5by the disease each year, and most of them die. Tsetse fly traps are a simplebut effect solution. They are built using blue cloth spread between three poles, 6that looks like a cow to the hungry insect, while bottles containing a mixture 7of cows' urine and acetone are placed below. Attracted by the smell, the tsetsefly settles on the cloth but is unable to get a bite and falls into the trap. One 8tsetse fly trap cost only ￡20 to build but tests have shown that a single trap 9will not work. For this reason it's important that farmers build a number traps 10across an area.