[tarice]

Also of note, and linked in the article, is the subject of Myxomatosis, a virus created to curb the population of rabbits in Australia.

https://en.wikipedia.org/wiki/Myxomatosis

[Someone]

Not created, introduced.

[bayesianhorse]

Also, rabbit haemorrhagic disease, which was investigated as a possible agent, then "escaped" from the lab "accidentally". Both didn't really work long-term.