Feral swine do more than $1.5 billion a year in damage around the country, and scientists are taking what could be a big step toward controlling them. They are field-testing poison baits made from a preservative that's used to cure bacon and sausage.The tests will cover two major habitats where feral hogs are common during seasons when they're most likely to go for bait, said Kurt VerCauteren, feral swine project leader for the U.S. Department of Agriculture Wildlife Services. Tests will start early in 2018 in dry west Texas and continue in humid central Alabama around midsummer. The bait Vercauteren is working on uses the meat preservative sodium nitrite. It can keep an animal's red blood cells from pulling in oxygen. Pigs make very low levels of an enzyme that counteracts it, so it's more deadly to them than to humans or most domestic animals. Swine that gobble up enough sodium nitrite show symptoms similar to carbon dioxide poisoning: They become uncoordinated, lose consciousness and die within 90 minutes after eating it.