New Zealand's biggest intentional biosecurity breach was in 1997, when Central Otago farmers imported the Rabbit Calicivirus (RCV) from Europe. The population dipped briefly, then returned as the naturally RCV-immune rabbits bred and replaced the dead RCV-susceptible rabbits. (It's believed that when young rabbits are exposed to the virus, they become immune -- so the virus killed older rabbits but the next generation took their place) <<a href="https://www.nzvna.org.nz/site/nzvna/files/articles/What%20is%20Rabbit%20Calicivirus.pdf" rel="nofollow">https://www.nzvna.org.nz/site/nzvna/files/articles/What%20is...</a>>