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Screwworm infests dog in Arizona, widening US cases

By Thomson Reuters Oct 28, 2026 | 4:58 PM

By Tom Polansek

WASHINGTON, Oct 28 (Reuters) – The US Department of Agriculture confirmed a case of the flesh-eating parasite New World screwworm in a dog in ​Arizona on Wednesday, widening infestations in the ‌US to a third state.

The first detection in Arizona was in Cochise County, which borders Mexico, according to the USDA.

The dog had a wound on its back that was infested with maggots, ‌consistent ​with screwworm, and scientific testing ⁠verified the infestation, the ⁠Arizona Department of Agriculture said.

“We have been preparing for this possibility for a long while and are acting swiftly,” State Veterinarian Dr. Ryan Wolker said in ​a statement.

The US halted livestock imports from Mexico last year to try to keep out screwworm but ⁠detected an infestation in a ⁠calf in Texas in June. It has ​since confirmed additional cases in Texas and New Mexico.

The import ​halt helped tighten US cattle supplies and push ‌beef prices to record highs for American consumers.

The USDA has resumed trade at three ports of entry in Arizona and New Mexico since August. The agency has ⁠said it next plans to restart livestock imports from Mexico in Nogales, Arizona, on November 30, if conditions for safe ⁠trade are ‌in place.

The USDA has confirmed 71 screwworm ⁠cases since June, and 18 are ​active, according ‌to its website. Infestations have multiplied ​since last ⁠month, when there were only two active cases.

Last week, the USDA confirmed the first case of screwworm in US wildlife in an elk in Texas.

(Reporting by Tom Polansek, Christian Martinez and Daphne Psaledakis; Editing by Jasper Ward ​and Rod Nickel)