Diseases From Pets Endanger Threatened Wildlife

Infectious diseases have contributed to at least 31 extinctions worldwide and currently jeopardize 43 threatened mammal species.

Parasites from domesticated animals especially pose a serious treat to the continuing existence of some of their wild relatives.

Among the mammals listed by IUCN (The World Conservation Union) as being threatened by diseases, 88 percent are either carnivores or ungulates. These animals are related to dogs, cats, cattle, goats, sheep and pigs.

Parasites threaten eight species of wild canines and three kinds of felines. Devastating infections are also a concern for 23 species of hoofed mammals related to cows, sheep, goats or pigs. In comparison, diseases do not endanger any of the 1024 species of bats, and affect only one of 2041 species of rodents.

In their analysis of IUCN Red List information on threatened wildlife, researchers conclude that a species is at highest risk of becoming decimated by disease simply if it's related to domesticated animals. The susceptible wild mammals are not inherently different from other animals in their size, lifespan, geographic range or natural parasite diversity.

This study identified 31 kinds of parasites responsible for population declines or hindering reproduction in wild animals. All but one of these culprits also infect pets or farm animals. More than 80 percent of parasites in cats, dogs or livestock are generalists that can harm a number of species, including wildlife. Surprisingly, many of the destructive organisms only spread among species when animals come in close contact.

A number of the diseases are well-known viruses, such as canine distemper, foot-and-mouth disease, rabies and rinderpest. Canine distemper alone has hampered the survival of ten predator species. Bacteria that are common among livestock, including anthrax and bovine tuberculosis, are also big offenders among wild mammals. Viruses and bacteria make up 80 percent of the pathogens; the rest are fungi, protozoa, arthropods such as mange, and parasitic worms like lungworm.

While diseases are a concern for only a minor portion of all threatened mammals, the information currently available likely underestimates the prevalence of diseases and their role in diminishing animal populations. Researchers found a lot of gaping holes in the data available on pathogens in threatened species. Most of the primates, carnivores and ungulates that are under the greatest threaten of extinction have never been scientifically investigated for parasites. Well-known instances of significant disease-caused devastations were also not included in the 2006 IUCN database, notably those caused by canine distemper in black-footed ferrets and bacterial infections in koalas.


Amy B. Pedersen, Kate E. Jones, Charles L. Nunn and Sonia Altizer. 2007. Infectious Diseases and Extinction Risk in Wild Mammals. Conservation Biology. 21(5): 1269-1279.

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