The Arizona Department of Agriculture announced Wednesday that a dog living on a ranch in Cochise County has been identified as the state’s first case of New World screwworm (NWS), a parasitic fly that feeds on the flesh of warm‑blooded animals.

What is New World screwworm?

According to the Centers for Disease Control and Prevention, the species Cochliomyia hominivorax completes part of its life cycle by laying eggs on living tissue. When the larvae hatch, they feed on the host’s flesh, causing painful wounds that can become serious if left untreated.

How the fly has spread

Historically, NWS has been confined to South America and parts of the Caribbean. Since 2023, however, the insect has migrated northward, moving through every country in Central America, into Mexico, and now into the United States. The U.S. Department of Agriculture reported the first animal case on June 3, 2026, in a livestock setting.

First U.S. case in a dog

While subsequent cases have been documented in sheep and cattle in New Mexico and Texas, the Cochise County incident marks the first confirmed U.S. infection in a dog. State officials emphasized that there have been no human infestations linked to the fly in the United States, and the overall risk to people remains very low.

Response and next steps

Arizona’s agricultural officials are working with local veterinarians to treat the affected animal and to monitor nearby livestock for any signs of infection. The department also urged ranchers and pet owners to inspect animals for unusual wounds and to seek veterinary care promptly if symptoms appear.

State health authorities continue to track the spread of the parasite and will provide updates as more information becomes available. Residents are encouraged to stay informed through official channels and to follow any guidance issued by the Arizona Department of Agriculture.

Original reporting: azfamily KTVK/KPHO Phoenix (news) — read the source article.