"How did the mouse population grow so large in the villages? MacKenzie noticed the remarkable lack of cats. He learned that, a few years earlier, in a well-meaning health measure, Bolivia had initiated a massive DDT-spraying campaign to eliminate malaria. However, the spraying also poisoned thousands of cats. As the cats died off, the mouse population rose. A well-intentioned government program inadvertently contributed to a deadly plague. Sometimes well-meaning mankind can be its own worst enemy."

No matter if you have an opinion on it or not - that's irrelevant really, just a comment I couldn't help but throw in - if you are interested in medical science, this is a good read.

Machupo - aka Why I don't think mandatory sterilization of cats should be a law