Update Note: This article reports new information involving the first New World screwworm detection in Arizona following Nature World News' earlier coverage of Texas cases. Latest verified figures: USDA case counts as of Wednesday, Oct. 28, 2026, as reported by Reuters; Arizona Department of Agriculture statements reported Oct. 28, 2026.

New World screwworm has reached Arizona. The U.S. Department of Agriculture confirmed on Wednesday, Oct. 28, that a household dog in Cochise County, which borders Mexico, was infested with the flesh-eating parasite, making Arizona the third U.S. state with cases after Texas and New Mexico.

A local veterinarian examined the dog on Oct. 26 and found a wound on its back that was "heavily infested with maggots consistent with NWS characteristics," the Arizona Department of Agriculture said, according to ABC15. Testing at a USDA Animal and Plant Health Inspection Service laboratory in Iowa confirmed the case. No further information about the dog's condition was released.

For Arizona pet owners, the practical message is immediate. The first case in the state was not a calf on a ranch but a family dog, which means people in southeastern Arizona should be checking their animals for wounds daily, not just watching livestock news.

A Third State and a Westward Shift

The USDA had reported 71 screwworm cases nationwide since June as of Oct. 28, with 18 active, Reuters reported. That marks a sharp rise in active cases from the seven active cases USDA listed as of Oct. 21.

Nature World News previously reported on the first screwworm case in U.S. wildlife, a Texas elk, and earlier on a Brewster County, Texas, dog that prompted wound-check advice for Texas pet owners. The Arizona case is different because it moves confirmed infestation into a new state, a new set of border ranchlands and a new wildlife landscape that includes deer, javelina and other warm-blooded animals.

Arizona officials said the state had prepared for this scenario — and moved quickly. "We have been preparing for this possibility for a long while and are acting swiftly," said State Veterinarian Dr. Ryan Wolker.

Inside the 20-Kilometer Zone

USDA and Arizona officials are establishing a 20-kilometer (about 12-mile) infested zone around the detection site. Inside that area, they are imposing animal movement controls, increasing live animal surveillance and trapping, releasing sterile flies, and reaching out to producers, veterinarians, and residents. Officials have not published the zone's exact boundaries, so residents in Cochise County should check with the Arizona Department of Agriculture before moving animals.

Sterile fly releases are the main eradication tool. Male flies sterilized by radiation mate with wild females, which then lay eggs that never hatch. Over time, the wild population collapses. The same method eliminated screwworm from the United States decades ago, and the USDA has already released more than 1 billion sterile flies in the current response, as Nature World News previously reported. Arizona has also planned a sterile fly dispersal facility in Douglas, also in Cochise County, though planning is ongoing.

The detection also reaches into cross-border trade. The USDA halted livestock imports from Mexico last year and has since resumed trade at three ports in Arizona and New Mexico. It plans to restart imports at Nogales, Arizona, on Nov. 30 if safe-trade conditions are met. Whether an Arizona case changes that timeline is not yet known.

Checking Pets, Livestock and Wildlife

Screwworm flies lay eggs in open wounds and natural body openings. Unlike common maggots that feed on dead tissue, screwworm larvae burrow into living flesh. Arizona officials urged owners to check animals daily for draining or enlarging wounds, maggots or egg masses in wounds, signs of discomfort or irritability, and lesions around the ears, nose, genital area, and navel.

Fresh wounds are the main risk — even small ones. That includes cuts from fences or brush, bite wounds, surgical incisions, ear tags, and the navels of newborn animals. Owners should clean and treat wounds promptly and call a veterinarian about any wound that seems to worsen or smells foul. Do not try to remove deep infestations at home.

Suspected cases in animals should be reported to the Arizona Department of Agriculture at 602-542-4293, weekdays from 8 a.m. to 5 p.m. MST, or by email to diseasereporting@azda.gov. Anyone who sees affected wildlife should note the GPS location and call the Arizona Game and Fish Department at 623-236-7201.

The USDA says screwworm "is a serious pest that affects livestock, pets, wildlife, and, less commonly, people." The CDC currently rates the risk to the public in the United States as very low and has reported no locally acquired human infestations. Screwworm is not a food safety issue.

Ranchers, Wildlife and Household Costs

The greatest burden in the near term falls on Cochise County livestock owners inside the movement zone, along with pet owners in rural areas where animals roam outdoors. Wildlife managers face a harder problem, since infested deer or javelina are difficult to find and treat. Hunters in southeastern Arizona should inspect harvested animals and report anything unusual.

There is also a household cost pathway. The pause on Mexican cattle imports tightened U.S. cattle supplies and contributed to record beef prices, according to Reuters. Any delay to the Nogales reopening could extend that pressure, though officials have not announced a change.

Key questions remain unanswered. Officials have not said where the dog was infested, whether more flies are active nearby, or whether the zone will expand. Surveillance trapping over the coming weeks will help answer those questions, and the USDA updates its case dashboard regularly.

The bottom line: screwworm is now in Arizona, and a family dog was the first sign. Southeastern Arizona residents should inspect pets and livestock daily, report suspicious wounds quickly, and watch for official updates on the quarantine zone.

Developing Story Timeline

Oct. 28, 2026: USDA confirms Arizona's first screwworm case in a Cochise County dog and announces a 20-kilometer infested zone, with 71 total U.S. cases and 18 active.

Oct. 26, 2026: A local veterinarian examines the dog and finds a maggot-infested wound on its back.

Oct. 21 to 22, 2026: USDA confirms the first U.S. wildlife case in a Texas elk, with 59 total U.S. cases and seven active as of Oct. 21.

June 3, 2026: USDA confirms the first U.S. case of the current outbreak in a Zavala County, Texas, calf.

What Readers Want to Know

What happened in Arizona? A dog in Cochise County was confirmed on Oct. 28, 2026, as Arizona's first New World screwworm case after a veterinarian found a maggot-infested wound on its back.

What is the 20-kilometer zone? It is an infested zone of about 12 miles around the detection site where officials are restricting animal movement, trapping flies, increasing surveillance, and releasing sterile flies.

What should pet owners look for? Check daily for draining or enlarging wounds, maggots or egg masses, foul-smelling sores, irritability, and lesions around the ears, nose, genitals or navel.

Can people get screwworm? It is possible but rare. The CDC says the current risk to the public in the United States is very low, with no locally acquired human cases reported.

Is meat from the grocery store safe? Yes. USDA says screwworm is not a food safety issue.

Where do I report a suspected case? Call the Arizona Department of Agriculture at 602-542-4293 for pets and livestock, or the Arizona Game and Fish Department at 623-236-7201 for wildlife.