For general questions contact Animal Industries
For media inquiries, contact Sydney Kennedy by email at media@isda.idaho.gov or phone at 208-332-8507
New World Screwworm in the U.S.
New World Screwworm (NWS, Cochliomyia hominivorax) has been detected in several states, view the infested zones here. NWS is a serious pest that affects livestock, pets, wildlife, and, less commonly, people and birds. Adult screwworm flies are about the size of a common housefly or slightly larger. Their larvae feed on the living tissue of warmblooded animals.
Idaho does not have any detections of New World Screwworm at this time.
Idaho’s Response
To protect Idaho’s livestock industry and trade interests, as well as the interests of all warm-blooded animals including pets, the ISDA has implemented an administrative order restricting entry of animals from states with New World screwworm infestations.
For all warm-blooded animals moving from a designated New World screwworm (NWS)-infested zone, a Certificate of Veterinary Inspection (CVI) issued within five days prior to movement into Idaho and copy of the movement permit from the state-of-origin that authorizes the animals to leave the infested zone are required.
For all warm-blooded animals originating from a state where NWS has been detected, but outside a designated NWS-infested zone, a CVI issued within five days prior to movement into Idaho is required.
Warm-blooded animals include but are not limited to all livestock, dogs, cats, cattle, bison, swine, poultry, sheep, goats, equines, rabbits, rodents, poultry, birds and domestic cervidae.
What to Look For
The name screwworm refers to the maggots’ feeding behavior as they burrow (screw) into an open wound of warm-blooded animals, 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.
Signs of screwworms in mammals and birds can include irritated behavior, head shaking, the smell of decay and the presence of fly larvae (maggots) in wounds. Photos of screwworm infested wounds can be found here.