New World screwworm cases climb to 19 in Texas, New Mexico

The number of confirmed New World screwworm cases in the United States has risen to 19, according to federal and state animal health officials, prompting expanded quarantine measures and renewed calls for livestock producers to remain vigilant.

Three new cases were confirmed this week in cattle in Terrell County, Texas, bringing the national total to 19. Eighteen of those cases are located in Texas, with one case reported in neighboring New Mexico. The detections represent the latest developments in what has become the most significant U.S. screwworm response effort in decades.

The first U.S. case of the 2026 outbreak was confirmed on June 3 in a calf in Zavala County, Texas. Since then, additional cases have surfaced across several counties in South and West Texas, primarily affecting cattle, goats, and other domestic livestock.

In response to the growing number of detections, the Texas Animal Health Commission has expanded quarantine restrictions in affected areas. Portions of multiple counties, including Terrell, Pecos, Uvalde, Val Verde, Webb, Zavala, Edwards, Gillespie, Kerr, Kimble, and Sutton, are now designated as New World screwworm-infested zones. Livestock and other warm-blooded animals cannot leave these zones without inspection and authorization from state animal health officials.

Producers moving animals outside quarantined areas must obtain movement certificates documenting animal identification and treatment protocols designed to prevent the spread of the parasite. State officials warn that unauthorized movement of animals could result in penalties and hinder eradication efforts.

Unlike common fly larvae that feed on dead tissue, New World screwworm larvae infest living tissue. Adult flies lay eggs in open wounds, navels of newborn animals, branding sites, tick bites, or other openings. After hatching, the larvae burrow into flesh, causing a painful condition known as myiasis.

If left untreated, infestations can lead to severe tissue damage, secondary infections, and death. Livestock species are particularly vulnerable, though the parasite can also affect wildlife, pets, and occasionally humans.

Because female screwworm flies mate only once, breeding with sterile males prevents viable offspring and gradually collapses the population. The U.S. Department of Agriculture and state officials have ramped up sterile fly dispersal operations across affected regions, including parts of West Texas where new cases have emerged. Experts caution that additional cases are likely to be identified in the coming weeks because sterile fly releases do not eliminate existing larvae already developing in animals.

With the screwworm life cycle lasting approximately three weeks, officials expect it will take several reproductive cycles before local populations begin to decline significantly.

The post New World screwworm cases climb to 19 in Texas, New Mexico appeared first on AGDAILY.