[ar:MP3 同步字幕版(英音)]
[ti:A Man-made Disease]
[by:更多学习内容,请到chazidian.com搜索“新概念”]
[00:01.55]Lesson 17
[00:03.76]A man-made disease
[00:12.84]What factor helped to spread the disease of myxomatosis?
[00:19.81]In the early days of the settlement of Australia, enterprising settlers unwisely introduced the European rabbit.
[00:28.27]This rabbit had no natural enemies in the Antipodes, so that it multiplied with that promiscuous abandon characteristic of rabbits.
[00:39.36]It overran a whole continent.
[00:41.81]It caused devastation by burrowing and by devouring the herbage which might have maintained millions of sheep and cattle.
[00:50.85]Scientists discovered that this particular variety of rabbit (and apparently no other animal) was susceptible to a fatal virus disease, myxomatosis.
[01:03.19]By infecting animals and letting them loose in the burrows, local epidemics of this disease could be created.
[01:11.15]Later it was found that there was a type of mosquito which acted as the carrier of this disease and passed it on to the rabbits.
[01:20.29]So while the rest of the world was trying to get rid of mosquitoes, Australia was encouraging this one.
[01:27.83]It effectively spread the disease all over the continent and drastically reduced the rabit population.
[01:35.04]It later became apparent that rabbits were developing a degree of resistance to this disease,