Flesh-eating New World Screwworm could pose health risks to cattle, humans

A threat to American livestock – the New World Screwworm (NWS) fly, which has been considered eradicated from the country since 1966 — has reemerged as a potential danger following an outbreak in Mexico.The news triggered a shutdown of cattle, horse and bison imports along the southern border, as U.S.Department of Agriculture (USDA) Secretary Brooke Rollins announced in an X post on Sunday.“Due to the threat of New World Screwworm I am announcing the suspension of live cattle, horse, & bison imports through U.S.

southern border ports of entry effective immediately,” she wrote in the post. “The last time this devastating pest invaded America, it took 30 years for our cattle industry to recover.This cannot happen again.”The NWS is a fly that is endemic in Cuba, Haiti, the Dominican Republic and some South American countries, according to the USDA’s Animal and Plant Health Inspection Service (APHIS).While the flies themselves are found in forests and other wooded areas, they will seek hosts like cattle or horses in pastures and fields, per the above source.A female fly lays eggs in a wound or orifice of a live, warm-blooded animal.

The eggs then hatch into larvae (maggots) that burrow into the flesh, causing potentially deadly damage.Screwworms are named for their maggots’ behavior, as they burrow into the flesh similar to how a screw is driven into wood.“Maggots cause extensive damage by tearing at the hosts’ tissue with sharp mouth hooks,” according to the APHIS website.This can then enlarge the wound and attract more flies to lay eggs.In rare cases, the larvae can feed on people, the Centers for Disease Control and Prevention states.These infestations can be very painful and can cause serious, potentially fatal damage to their hosts by causing myiasis, a parasitic infection of fly larvae in human tissue. Screwworms are often found in South America and the Caribbean.“People who travel to these areas, spend time among livestock anima...