The United States Department of Agriculture Animal and Plant Health Inspection Service said they are releasing 100 million sterile flies near the Rio Grande Valley to stop the northern spread of New World screwworm.

The New World screwworm is a parasitic fly that lays eggs in the living tissue of fresh wounds in warm-blooded animals, according to the Texas A&M Agrilife Extension. The larvae, or maggots, feed on the host’s flesh, causing severe wounds and often death if untreated.

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According to a news release, the USDA will reallocate aircraft and sterile insects to reinforce coverage along the U.S.-Mexico border. The new dispersal area will include operations 50 miles into Texas and also with the state of Tamaulipas, Mexico.

Several cases of screwworm have already been reported in Tamaulipas, located 215 miles south of the Valley.