New World Screwworm inches closer to the Texas border; flesh-eating larvae can be deadly to cattle

Brahman cows graze near Mercedes, Texas, about 11 miles 
from the Mexico border. (Photo by J. Carrico, Farm Journal)

After a few months of reduced sightings, the New World Screwworm is making news again. "Mexican authorities confirmed an NWS case in a seven-year-old bovine and a 6-day-old calf both on Jan. 5," reports Jennifer Carrico of Progressive Farmer. Both infected animals were less than 220 miles from the U.S.-Mexico border.

Despite efforts by the U.S. Department of Agriculture and Mexican authorities, NWS has inched closer to the Texas border. The parasite has spread north even as Mexico has strictly limited cattle movement across the country.

Texas Agricultural Commissioner Sid Miller told Carrico, "The screwworm now may be moving closer on its own, with no apparent link to commercial animal movement. Texas producers must act now -- stay informed, stay vigilant, and prepare immediately. We cannot drop our guard for even a moment."

NWS flesh-eating larvae can be deadly to cattle and other warm-blooded animals, including sheep, horses and dogs. Female NWS deposit their eggs in an animal's open wound, and once the larvae hatch, they eat away at the host's flesh, which can cause infection and decay. "The larvae can kill an animal in just four to seven days if not quickly detected and treated," reports Stump Denton of Farm Journal.

Since female NWS mate only once in a lifetime and store their fertilized eggs, releasing millions of sterile male NWS has been the best way to eradicate harmful larvae production. Carrico explains, "The USDA eradicated NWS from the United States in 1966 using the sterile insect technique, and it was used successfully again in 2016 in the southern Florida Keys when found in deer."

A sterile fly distribution facility at Moore Airbase in Edinburg, Texas, is expected to be up and running early this year.