screwworm

More Funding for Screwworm Management

DanCattle, Disease

screwworm
Screwworm larva. Tusklike mandibles protruding from the screwworm larva’s mouth rasp the flesh of living warm-blooded animals. A wound may contain hundreds of such larvae.
By John KucharskiTransferred from en.wikipedia to Commons. Original uploader was Ellmistfrom
screwworm
New World screwworm (NWS, Cochliomyia hominivorax) is a devastating pest. When NWS fly larvae (maggots) burrow into the flesh of a living animal, they cause serious, often deadly damage to the animal. NWS can infest livestock, pets, wildlife, occasionally birds, and in rare cases, people.
Courtesy of USDA/APHIS

The Agriculture Department has allocated additional resources to respond to recent cases of New World screwworm in livestock in southern Mexico and Central America. Rusty Halvorson has more.

More Funding for Screwworm Management

What to Look For

The name screwworm refers to the maggots’ feeding behavior as they burrow (screw) into the wound, feeding as they go like a screw being driven into wood. Maggots cause extensive damage by tearing at the hosts’ tissue with sharp mouth hooks. The wound can become larger and deepen as more maggots hatch and feed on living tissue. As a result, NWS can cause serious, often deadly damage to the animal.

Adult screwworm flies are about the size of a common housefly (or slightly larger). They have orange eyes, a metallic blue or green body, and three dark stripes along their backs.

Report mammals and birds with the following signs:

  • Irritated behavior
  • Head shaking
  • The smell of decay
  • Evidence of fly strike
  • Presence of fly larvae (maggots) in wounds

Pest Alert | New World Screwworm (356.21 KB)(also in Spanish (348.54 KB))

Brochure | New World Screwworm: What You Need To Know (3.48 MB) (also in Spanish (4.26 MB))

Poster | Screwworm: An International Threat to Human and Animal Health (958.86 KB)