New World Screwworm Infestation Spreads to Arizona, Affecting Domestic Pets

Overview of the Parasitic Spread

The New World Screwworm (NWS) infestation has officially reached Arizona, marking the third US state to report cases since the parasitic flies re-entered the country in June. While the majority of the 74 confirmed US cases have involved livestock, health authorities have documented a rise in attacks on domestic animals, including pets.

Understanding the Infestation

• The Mechanism: Screwworm flies deposit eggs into existing wounds or moist orifices. Upon hatching, the larvae, which resemble screws, burrow into living tissue.
• Historical Context: These flies were previously eradicated in the US during the 1960s using sterile insect technology. Following a breach in the biological barrier at the Darién Gap in 2022, the parasites have migrated northward through Central America.
• Current US Statistics: Since June, 74 cases have been identified across Texas, New Mexico, and Arizona. This total includes 10 cases involving domestic pets and one report of an infected wild elk.

Recent Developments in Arizona

The Arizona Department of Agriculture reported an index case in Cochise County on October 26. A local veterinarian identified the infestation in a dog, noting wounds consistent with NWS characteristics. The US Department of Agriculture (USDA) is collaborating with state officials to manage the response and monitoring efforts.

Guidance for Pet and Livestock Owners

Officials urge animal owners to remain vigilant and report any suspicious wounds immediately. Pet owners are advised to conduct regular physical checks of their animals. For verified updates and official alerts, owners should consult the USDA or their respective state agriculture departments.

Reported Risks and Data

While livestock remains the primary concern for agricultural impact, Mexico’s Ministry of Health has reported 806 human cases since the flies' reemergence in that region, including nine fatalities. While human cases are rare, the situation highlights the invasive nature of the parasite.