More screwworm cases ID’d in Texas livestock, New Mexico dog

The number of active New World screwworm cases detected in the United States rose to 10 by Friday morning, up from six on Wednesday, according to the U.S. Department of Agriculture. The June 3 discovery of the parasitic blowfly larvae in Texas was the first U.S. case in nearly 60 years. The new cases of the parasitic worms were found in domestic livestock, including goats and cattle, in Texas’ Edwards and Zavala counties. The first few U.S. cases of screwworm were only in cattle. A dog in New Mexico was confirmed to have the parasite on June 8.

All 10 active cases on Friday were located in four Texas counties and Lea County in southeast New Mexico. The affected animals were undergoing treatment and wound management, and none had yet recovered or died, according to the USDA.

Screwworm flies lay eggs in animals’ wounds and body openings. The parasitic larvae hatch and burrow into living flesh, causing infections that can kill livestock. The pests spread throughout Central America and Mexico over the past few years before their first recent detection in the United States.

What strategies are authorities using to combat the spread of screwworm? Strategies include case tracing, wound care, and releasing millions of sterile flies into affected areas to disrupt the screwworms’ reproduction. All ports of entry on the southern border are also closed to livestock trade to prevent the inflow of more animals that might be infected.

The Food and Drug Administration on Thursday also authorized emergency use of an over-the-counter drug to treat screwworm cases in dogs and cats.

Dig deeper: Read Christina Grube’s report on the first recent U.S. case of screwworm.