The dog had no known travel history, according to the Arizona Department of Agriculture. It was found roughly 75 miles from the state's first case and about 32 miles from the nearest active infection, a distance that raised concern among officials tracking the outbreak's spread.

Under federal rules, the department established a 12.4-mile (20-kilometer) infested zone around the affected property. No animals may leave the zone until restrictions are lifted unless the state veterinarian grants approval, and owners are barred from conducting their own inspections while the zone remains active.

The four earlier Arizona cases involved a sheep and a horse in Greenlee County and a dog and a horse in Cochise County.

Screwworm is the larval stage of a parasitic fly that burrows into the living tissue of warm-blooded animals and, in rare instances, people. The pest was largely wiped out in the United States in the 1960s but resurfaced in Mexico in 2024, and the U.S. Department of Agriculture is now releasing sterile flies in the region and constructing a dispersal facility in Douglas.

State officials scheduled a public meeting for Graham and Greenlee county residents from 5 to 7 p.m. Tuesday at the Lee Little Theater at Eastern Arizona College in Thatcher. Agriculture Director Paul Brierley and State Veterinarian Ryan Wolker are expected to take questions from the community.

Residents who spot a wound that appears infested with maggots are urged to report it to diseasereporting@azda.gov. Wildlife sightings should be directed to the Arizona Game and Fish Department.

The expansion into Graham County marks the furthest north the quarantine has reached since the outbreak began, putting ranchers, pet owners and rural households across the region on heightened alert.