Rabbits

Rabbits have been a source of environmental problems when introduced into the wild by humans. 
As a result of their appetites, and the rate at which they breed, feral rabbit depredation can be problematic for agriculture. 
Gassing, barriers (fences), shooting, snaring, and ferreting have been used to control rabbit populations, but the most effective measures are diseases such as myxomatosis (myxo or mixi, colloquially) and calicivirus. In Europe, where rabbits are farmed on a large scale, they are protected against myxomatosis and calicivirus with a genetically modified virus.