Isolation, and the acceptance of quarantine and disease control, have kept New Zealand livestock free of the more serious epizootic diseases which still ravage domestic and wild animals in Europe, Asia, and the Americas. Except for the Maori dog and rat introduced in the fourteenth century, there were no land mammals in New Zealand until Captain Cook released pigs, goats, and sheep on his second voyage in 1773. Only the pigs survived. Cook introduced more domestic animals on his third voyage (1777) and, from the end of the eighteenth century, whalers, sealers, missionaries, and the first small groups of settlers imported some few animals. All present species of domestic animal in New Zealand were established during the immigration of the 1840s.

Sheep scab, a serious skin disease due to infestation with the mange mite Psoroptes communis ovis, was recognised in 1849 and a Scab Ordinance was passed. Scab was eradicated by 1880 through rigorous measures including, in the later stages of the campaign, the slaughter of diseased animals. Bovine pleuro-pneumonia appeared in the South Island in 1864. The seriousness of the disease was recognised; it was eradicated by slaughter. Virus swine fever was recorded between 1895 and 1902, but did not become endemic. It has since been successfully excluded, except for two outbreaks in 1932 and 1953 close to the ports of Wellington and Auckland. Both outbreaks, caused by the illegal introduction of virus-infected meat in ships' garbage, were quickly eradicated. Scrapie, a serious disease of sheep of obscure origin, appeared in 1952 in a South Island flock which had imported stud animals, and there was a second outbreak on another property before the disease was eradicated.

In 1876 an Act was passed “to restrict the importation of cattle and other animals into the Colony of New Zealand”; section 2 prohibited the entry of “all cattle, sheep, horses, swine, goats, and other animals … which are likely to propagate any infections of contagious disease amongst men or animals”. Since then the enactments controlling the importation of animals and animal products and stipulating the conditions of their entry have been made progressively more stringent to maintain New Zealand's relative freedom from communicable animal diseases.