From National Geographic:

An explosion of wild pigs in the U.S. could be exposing people to dangerous parasites, a new study says.

The wild pig, Sus scrofa, was first introduced to the U.S. from Europe as livestock in the 1500s, but over the years many animals have escaped captivity.

Today there's an estimated four million wild pigs spread across 39 states, with large populations in California, Texas, and the Southeast, according to the study.

Because they're so hardy and can eat almost anything, feral pigs have been living high on the hog, producing several litters of piglets a year, said study co-author Chris DePerno, an ecologist at North Carolina State University in Raleigh.

Mixed into this group are escaped domestic pigs, Sus scrofa domesticus. (See pictures of unusual domesticated animals, including a Vietnamese potbellied pig.)

Within two generations out of captivity, domestic pigs usually lose their pink hue and turn striped and coarse-haired, DePerno said, allowing them to blend in with feral populations.

For more, see: Wild Pig Explosion May Spread Disease to Humans