In the 18th century, the European rabbits (Oryctolagus cuniculus) were introduced in Australia. The first fleet arrived in 1778 by the European colonialist for several reasons. Here are the key reasons why these animals and pets were introduced in this country.
As a source of food – proteins
The first reason why they were introduced in Australia was to be a source of food. Rabbit meat is an excellent source of lean meat that has low fats, high amount of good proteins, and almost cholesterol free.
Also, due to their high breeding power, they were to provide a readily available source of meat in homesteads. These pets are prolific breeders and have been associated with the goddess of fertility in German if you know the Easter bunny myth.
Companion to settlers
Besides being a source of food, settlers brought these animals to Australia as companions (pets)  Although some escaped to the nearby bushes, they failed to survive and most of them died.
For sport hunting
Furthermore, wild European rabbits were introduced for hunting purposes. For instance, in Tasmania in 1827, feral rabbit colony was reported.
Later in 1859, on Christmas eve, some 13 more were set free in Victoria by Thomas Austin, i.e., “a self-made wealthy settler, released 13 European wild rabbits on his estate, Winchelsea, Barwon Park, Victoria.”  These were collected and sent to him by his relatives who were still in Europe.
Unexpectedly, their population exploded quickly in Winchelsea due to good grounds, abundant sources of food as well as the absence of predators.
By 1880 these animals had crossed the Murray River and by 1886, they “were found throughout that Victoria and New South Wales – even extending to the Northern Territory by the 1900s.”
Their population rapidly grew to about 10 billion in 1920. Currently, there are over 200 million wild and feral bunnies in Australia.
Population explosion and plagues
The abundance of food, favorable mild winter climate that allowed them to breed throughout the year and the absence of predators led to a rapid increase in this animal’s population making them the fastest mammal spread to be ever recorded.
Although they were a good source of food and source of income to those trapping them during the 1890s to 1930s economic depression, their huge population had devastating ecological effects until the Australian government began looking for control measures.
“Throughout the 19th and 20th centuries, different methods of rabbit control were tried, including trapping, rabbit warren ripping, fumigation and bounty systems.” 
Also, to control their population in Australia, there has been a deliberate introduction of myxomatosis virus as well as the rabbit hemorrhagic disease virus (RHDV).
Furthermore, this country does not have vaccines for these two deadly viral diseases for the fear of the wild bunnies here developing resistance against the two viruses.