At Mahr's ranch outside Tuxtla Gutierrez, a worker lassos a young cow. The animal bucks as it is guided over to Mahr, who is waiting with an aerosol can of disinfectant used to clean the wound left from removing the animal's horns.

Officials say the screwworm has the potential to devastate the cattle industry, send beef prices soaring and kill wildlife.

The U.S. Department of Agriculture will spend up to $750 million to build a sterile fly production facility in Texas to fight the flesh-eating livestock pest New World screwworm, USDA Secretary Brooke Rollins said on Friday.