By Julie Tomascik
Editor
A destructive parasite found in livestock and other warm-blooded animals was identified in November in Mexico.
The New World screwworm was found in a cow at an inspection checkpoint in the southern Mexico state of Chiapas, close to the border with Guatemala.
“Finding a screwworm in Mexico means the pest is right at our border. If the pest becomes established in the U.S. again, it could have a devastating impact on the livestock industry and for wildlife,” Tracy Tomascik, Texas Farm Bureau associate director of Commodity and Regulatory Activities, said.
The Texas Animal Health Commission (TAHC) is working closely with USDA to implement existing response plans to enforce pest monitoring at Texas’ southern border and into the state.
To prevent the northward movement of the pest, cattle imports from Mexico were suspended in November.
“Shipments will likely resume incrementally after the New Year, with full resumption of live animal movements sometime after that,” Dr. Rosemary Sifford, USDA’s chief veterinary officer, said in a statement.
In order to resume shipments, Mexico must set up USDA-approved holding pens where inspectors will check and treat Mexican cattle for screwworms before they cross the border. USDA will inspect Mexico’s pens, according to Jennifer Lester Moffitt, USDA undersecretary for Marketing and Regulatory Programs.
USDA also approved an emergency round of funding in December to aid the production and dispersal of sterile screwworm flies in Central America.
“The focus is to stop their movement north so sterile flies are being released in southern Mexico to make that happen,” Tomascik said. “They’re in a relatively narrow land area down there, which makes a quick and effective response even more critical.”
Screwworm larvae burrow into the skin of living animals, causing serious and often fatal damage.
One female fly can lay 200-300 eggs at a time and may lay up to 3,000 eggs during her lifespan, according to USDA.
To eradicate the pest, sterile male flies are bred to mate with fertile female flies, which only mate once in their lifetime. The screwworm population decreases until it eventually dies out. This is how the pest was eradicated from the U.S. in 1966 and later in 2016 when the screwworm was confirmed in Florida.
Adult screwworm flies are about the size of, or slightly larger, than a common housefly. They have orange eyes, a metallic blue or green body and three dark stripes along their backs.
Clinical signs of a New World screwworm infestation in livestock include: irritated or depressed behavior, loss of appetite, head shaking, smell of decaying flesh, evidence of fly strike, presence of fly larvae in wounds and isolation from other animals or people.
“If you suspect suspicious wounds, maggots or infestations, immediately notify your veterinarian,” Tomascik said.
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