Flesh-eating New World Screwworm infestations have spread to a third US state, Arizona, as the horrifying parasites increasingly target domestic pets and livestock near the southern border.
Parasite Spread and Impacts
Arizona joins Texas and New Mexico as states currently plagued by the parasites. A total of 74 animal cases have been identified in the United States since the flies re-invaded the country in June, including recent attacks on four dogs and a cat within a single week.
The flies lay hundreds of eggs inside wounds and moist orifices of animals, after which the resulting maggots consume their hosts. These voracious larvae resemble screws and forcefully bore and twist into living flesh, causing severe and potentially fatal wounds before dropping to the ground to mature into adults.
Eradication History and Recent Breaches
Due to their devastating impact on livestock, authorities successfully eliminated the flies from the country in the 1960s using aerial releases of sterile male flies to disrupt successful breeding. A biological barrier maintained along the Darién Gap between Panama and Colombia kept the flies at bay for decades. However, that barrier was breached in 2022, allowing the insects to migrate back northward through Central America.
While primarily recognized as a major threat to the livestock industry, the pests can also devastate wildlife, household pets, and occasionally humans. Recent data from Mexico’s Ministry of Health shows that the country has confirmed 806 human screwworm infestation cases since the reemergence, resulting in nine deaths.
