New World screwworm case in Cochise County raising concerns among ranchers

A New World screwworm case in Cochise County is putting southern Arizona ranchers, livestock owners and pet owners on alert, with state officials now reporting two confirmed animal cases in the region. The parasite has been found in a ranch dog near Elfrida and in a domesticated horse near Hereford, about 10 miles west of Bisbee. The developments matter in Tucson because the region’s livestock industry, veterinary services and animal transport networks connect communities across Southern Arizona, including the Marana Stockyards and Livestock facility.

The Arizona Department of Agriculture confirmed the state’s first case after the parasite was detected in a dog that lived on a ranch near Elfrida, roughly 21 miles northeast of Bisbee. The dog spent substantial time outdoors and around livestock, according to information provided to 13 News. The Cochise County Health Department said the animal is receiving care. The second case was found in a horse near Hereford, approximately 45 miles from the original case. Agriculture officials said the horse is domesticated and had not traveled.

In response to the horse case, the state established a mandatory infested zone covering a 12.4 mile radius around the property. Livestock, horses and pets cannot be moved out of that area unless they are examined by the state veterinarian. Officials are urging people who care for animals to inspect wounds closely and report injuries that appear to contain maggots consistent with New World screwworm. The restrictions and inspections are intended to limit the parasite’s movement while officials determine the extent of the threat in the area.

New World screwworm is a parasitic fly whose larvae feed on the living tissue of warm blooded animals. The flies are drawn to open wounds, where they lay eggs. After the eggs hatch, the larvae can burrow into and consume living tissue. Dogs, cats, livestock and, in rare cases, people can become infected. Without treatment, severe infestations can be fatal. Veterinarians say livestock are especially vulnerable to serious outbreaks, raising concern for cattle operations throughout Southern Arizona.

The potential consequences are both medical and financial. Clay Parsons, manager of Marana Stockyards and Livestock, said the loss of cattle could place another burden on ranchers already managing the costs and risks of raising animals. He estimated that a lost animal could represent a loss of about $1,000 to $1,200. If many animals were affected, he said, those losses could eventually be reflected in prices paid by consumers. Parsons said ranchers need to fight the parasite aggressively before it becomes established and spreads more widely.

The Marana stockyards have begun taking additional precautions, including fogging selected areas to help control flies. No cases have been confirmed among livestock at the facility, but Parsons said ranchers have been watching the threat for some time. He described a potential spread as a major undertaking, while expressing confidence that Arizona ranchers know how to monitor cattle and respond to problems. For stockyards, ranchers and animal owners, the immediate focus is on prevention, early detection and limiting opportunities for infected animals or flies to move.

Veterinarians are advising owners not to panic, but to examine animals regularly, especially those that spend considerable time outdoors. Any wound deserves attention, since an open injury can provide an entry point for the parasite. Owners should seek veterinary care for animals with suspicious wounds or signs of infestation. Some medications used for parasite control may also be effective against screwworm, but veterinarians recommend consulting a professional before choosing a treatment. Emergency veterinary services can assist when an animal needs immediate attention.

Arizona had been preparing for the parasite before the Cochise County cases were confirmed. A little more than a month before the first Arizona case, organizations across the state were working on plans for its possible arrival. Earlier this year, the U.S. Department of Agriculture awarded the University of Arizona a $3.74 million grant to increase the state’s preparedness. The grant adds to efforts to develop the expertise and response capacity needed if the parasite threatens more animals or expands into additional areas.

For now, state officials are asking animal owners to remain vigilant, follow movement restrictions and report suspicious infestations. The confirmed cases are concentrated in Cochise County, but the concern reaches Tucson because Southern Arizona’s ranching economy and animal services are interconnected. Ranchers will continue monitoring their livestock, while facilities such as the Marana stockyards are using added fly control measures. The state’s inspections, the infested zone around the Hereford property and early veterinary care will be important in determining whether the parasite can be contained.