Arizona Confirms Its First New World Screwworm Case in a Cochise County Dog

The Arizona Department of Agriculture and the U.S. Department of Agriculture announced Arizona’s first case of New World screwworm on October 28, the Arizona Game and Fish Department said in a news release. The case is a dog in Cochise County.

New World screwworm is a parasitic fly that threatens wildlife, livestock, pets and, rarely, people. Its eggs hatch into larvae that feed only on living tissue.

A local veterinarian examined the dog on the evening of October 26 and found a wound on its back heavily infested with maggots. Scientific testing verified the species.

The department asked hunters and other outdoor recreationists to check harvested game and watch live animals they see. It noted that a hunter helped detect the first U.S. wildlife case, in an elk in Texas. Two signs to look for:

• Larvae on live or very recently dead animals. Unlike other maggots, screwworm larvae leave an animal once it has died and the tissue cools.
• Maggots deep in tissue with a foul odor, commonly at wounds or at the nose, eyes or genitalia.

If you suspect screwworm, take a GPS location and, if possible, pictures of the wound, larvae or affected animal. For wildlife, call Game and Fish immediately at 623-236-7201 and do not handle or transport the animal. For livestock or pets, contact the Arizona Department of Agriculture at the email address given in the release. If in doubt, ask your veterinarian.

The dog is under veterinary care. As of the October 29 release, the agriculture department was working with the veterinarian and the owner to gather information to guide any epidemiologic investigation and local response actions. Game and Fish is supporting that effort with USDA, and more information is at azgfd.gov/screwworm.