Feral hogs (Sus scrofa) are not native to North America but were transported to this continent from Europe and Asia.
The most recent expansion of feral hogs in the U.S. has been human-caused and includes illegal releases; highest populations are mainly in TX and FL. Only six states remain feral hog free—Montana, Wyoming, Utah, Connecticut, Delaware and Rhode Island (Jack Mayer S.C. pers. comm.). There are estimated to be more than 5 million wild hogs in the U.S.
Feral hog damage includes destruction by rooting in pastures, rangeland and riparian habitat, consumption of native vegetation, negative effects on water quality, and predation of wildlife. Economic impact is estimated at $1.5 billion/year. Feral hogs also carry diseases that can affect people, domestic animals, livestock and wildlife, as well as local water supplies.
USDA-APHIS initiated a national $20 million program in August 2015 to help states deal with a rapidly expanding population of invasive wild swine. Prevention, early detection and rapid control is practiced in states that are feral hog-free.
More information available at: http://www.scientificamerican.com/article/can-wild-pigs-ravaging-the-u-s-be-stopped/