Arizona has confirmed its first case of New World screwworm in an animal after the flesh-eating parasite was detected in a dog, making it the third U.S. state to report an infection, state and federal agriculture officials said.

The case was reported in Cochise County in southeastern Arizona, which borders Mexico, according to the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service. The canine was examined by a local veterinarian Oct. 26 after a wound on its back was found to be heavily infested with maggots that appeared consistent with New World screwworm (NWS), the Arizona Department of Agriculture said.

Scientific testing conducted in coordination with federal officials later confirmed the infestation. The dog is receiving veterinary care, and state officials said they are working with the veterinarian and owner to gather information to support an epidemiological investigation and determine any necessary local response measures.

"We have been preparing for this possibility for a long while and are acting swiftly," State Veterinarian Dr. Ryan Wolker said in a statement Oct. 28. "Because of the extensive outreach, coordination, and surveillance already in place, Arizona producers, veterinarians, and pet owners know what to look for and how to report suspected cases."

The Arizona case comes as authorities continue to track the northward spread of the parasite, which was eradicated from the United States decades ago. In recent years, it has spread north from Central America through Mexico.

As of Oct. 29, the USDA reported 74 NWS cases in animals across Texas, New Mexico and Arizona. Last week, the agency confirmed the first case of NWS in U.S. wildlife after the pest was identified in a hunter-harvested elk in West Texas.

In June, the USDA confirmed the presence of NWS in a 3-week-old Texas calf, marking the first known U.S. case in decades and the closest the parasite had come to reestablishing itself north of the Mexican border since its eradication in the 1960s.

Arizona expands surveillance, control measures

Federal and state officials said they are implementing response measures that include establishing a 12-mile infested zone around the detection site, restricting animal movement in the area, increasing live-animal surveillance and trapping, releasing sterile flies and conducting outreach to producers, veterinarians and local communities.

Arizona officials said they also have advocated for sterile fly releases in the area to suppress the pest and prevent it from becoming established. Officials confirmed that plans for a sterile fly dispersal facility in Douglas, Arizona, are continuing to move forward.

The USDA is urging livestock and pet owners in the area to check animals daily for enlarging or draining wounds, maggots or egg masses in wounds, signs of discomfort or irritability and lesions around body openings. Anyone who suspects an infestation should immediately contact a veterinarian, state agriculture officials or the USDA.

"New World screwworm is a serious pest," the USDA said in a statementOct. 28. "The larvae feed on living tissue and can cause severe wounds, animal suffering, and significant economic impacts if not detected and treated quickly."

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