A resurgent livestock pest has been making a lot of headlines lately.
The New World screwworm (NWS) was eradicated from the U.S. in the 1960’s, according to Extension educators at Texas A&M University. In a recently published bulletin, they noted there are occasionally flare-ups of the pest in Central America and Mexico.
Currently there is an NWS outbreak in progress in Central America. U.S. Secretary of Agriculture Brooke Rollins recently closed the border to livestock imports from Mexico after learning the pest was detected less than 700 miles from the U.S.-Mexico border. The ban applies to imports of cattle, horses, and bison, although NWS attacks all warm-blooded species, including wildlife and humans.
The screwworm gets its name from the unusual feeding behavior of its larvae (maggots) that “screw” into the host’s tissue with sharp mouth hooks. Over time and continued larval feeding and reproduction, these wounds become larger and deeper, causing extreme pain, tissue damage, and sometimes even death.
The Texas A&M educators advise producers to regularly check their livestock for potential NWS infestation. Symptoms include:
- Foul-smelling wounds with visible maggots;
- Animals biting and licking at wounds;
- Lesions in navels, ears, and dehorning and branding sites; and
- Unusual restlessness or lethargy.
They shared that typical livestock insecticide treatments may not contain an NWS outbreak because of the difficulty in targeting wildlife for treatment. In the past, the only way outbreaks have been brought under control is via release of sterile males, known as the sterile insect technique (SIT).
Producers who suspect a case of NWS infestation should immediately quarantine affected animals and report the case to their local veterinarian or wildlife biologist.
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