U of A offers New World screwworm testing kits to livestock producers

Tucson area livestock owners, veterinarians and people caring for pets should watch for signs of New World screwworm after four cases were confirmed in Arizona. The University of Arizona is making testing kits available at nearly every Cooperative Extension location so producers can collect suspected maggot samples and send them to a laboratory. The parasite can affect cattle, sheep, goats, horses, dogs, cats, wildlife and people, making the response relevant beyond ranches and farms. A public information session in Tucson will bring together animal health, public health and veterinary experts to explain what residents should look for and how they can help protect animals.

New World screwworm is a parasitic fly, not an ordinary nuisance insect. Its larvae enter living tissue through an open wound and feed as they burrow deeper, creating severe injuries that can become fatal without treatment. Flavie Audion, a University of Arizona rangeland management specialist, described the larvae as having structures that allow them to penetrate and remain in an animal. Because animals may be spread across large, remote pastures, ranchers cannot always inspect every one daily. An unnoticed wound or behavioral change can therefore become a serious problem before someone recognizes it.

The Arizona Department of Agriculture says a confirmed case triggers a mandatory Infested Zone extending 20 kilometers, or 12.4 miles, around the detection. Live animals may not leave such a zone unless the state veterinarian authorizes their movement. Veterinarians, livestock producers and animal owners are required to immediately report suspected infestations, unusual larvae or signs of the parasite in an open wound to the Office of the State Veterinarian. People who are concerned about an animal can also contact their veterinarian or the U.S. Department of Agriculture. The restrictions and reporting rules are intended to identify infections quickly and limit opportunities for the pest to spread.

Federal officials plan to use targeted releases of sterile flies as part of the response. The method was developed through research that accelerated in the 1930s and became central to earlier eradication campaigns. Sterile male flies mate with wild females, but the resulting eggs do not hatch. Repeated releases can gradually reduce the reproductive population. New World screwworm was eliminated from the United States decades ago through a coordinated effort between the United States and Mexico that combined sterile fly releases with surveillance, public education and awareness. The historical success provides a model, but current officials are emphasizing early detection and preparation.

The University of Arizona is expanding that preparation with a $3.74 million Grand Challenge Grant from the USDA. The project was assembled by Amy Ganguli, an extension specialist in the College of Agriculture, Life and Environmental Sciences, with input from the Arizona Cattle Growers’ Association, veterinarians, government agencies and conservation organizations. Its participants include specialists in veterinary diagnostics, entomology, agricultural economics, social science, precision livestock technology and Cooperative Extension. The team plans to estimate the pest’s possible economic effects on Arizona and compare response options, including the potential value of an Arizona based facility for distributing sterile flies.

One part of the project focuses on making diagnosis faster and more widely available. At present, trained entomologists generally identify individual larvae or flies by examining their physical characteristics, a process that requires years of specialized experience. Emily Janovyak of the Arizona Veterinary Diagnostic Laboratory is leading work to validate a PCR based test that could supplement the established method. PCR is already used for many foreign animal diseases and can support larger testing volumes through laboratories with molecular testing expertise. The kits now available through Cooperative Extension give producers a practical way to collect material for that diagnostic process.

Researchers are also studying ways to monitor animals across Arizona’s expansive rangelands. Audoin will evaluate virtual fencing collars and satellite connected GPS ear tags, tools that ranchers already use for grazing management. Movement and physiological information could help identify reduced activity, repeated head shaking or other changes that signal illness and prompt a closer inspection. Because wildlife and free ranging animals can help carry the parasite, Leigh Combrink, a wildlife disease and conservation specialist, will develop risk maps using ecological information, weather patterns and the distribution of livestock, wildlife and companion animals. Machine learning will be used to forecast where risk could rise over time.

Outreach is another major element of the grant. Cooperative Extension plans hands on workshops, virtual reality exercises for practicing inspections and sample collection, and mobile livestock handling units with corrals, squeeze chutes and testing equipment. Those units could reach remote areas if an outbreak occurs. The project will also collect 50 oral histories and hold five focus groups in Arizona, New Mexico and Texas to preserve lessons from ranchers and animal health workers who managed screwworm before its eradication in the 1970s. The effort is designed to serve all 15 Arizona counties and 22 federally recognized tribes, while strengthening the response network led by the state veterinarian’s office and the Arizona Livestock Incident Response Team.

For Tucson residents, the immediate opportunity to learn more is a Nov. 10 discussion at 5:30 p.m. in Room B109 at Drachman Hall, 1295 N. Martin Ave. Representatives of Pima Animal Care Center, the Pima County Health Department, the Arizona Department of Health Services, the Arizona Department of Agriculture, the U of A College of Veterinary Medicine and the Zuckerman College of Public Health are scheduled to participate. They will address risks to pets, livestock and other animals, signs that warrant attention and steps owners can take. Producers who find suspicious larvae should use an available kit when appropriate and report the concern without delay rather than waiting for the condition to worsen.