As of late December, New World Screwworm (NWS), Cochliomyia hominivorax, continues to be a significant animal and human health issue in Central America and Mexico. As of December 12, 2025, according to the Centers for Disease Control and Prevention (CDC) and the United States Department of Agriculture (USDA), over 140,000 animal cases and more than 1,000 human cases have been reported in these countries. The only confirmed NWS case in the United States (US) occurred in a human. The traveler-associated case was confirmed on August 4, 2025, by the CDC in cooperation with the Maryland Department of Health. As of December, the US border with Mexico remains closed to livestock trade.

The USDA continues to monitor the US–Mexico border. NWS fly traps are deployed by the Animal and Plant Health Inspection Service (APHIS) in Texas, New Mexico, Arizona, and California. Over 30,000 trapped flies have been analyzed, as well as more than 6,000 wild animals. On November 21, 2025, the USDA reported that NWS has not been detected in animals or traps in the US.

In Mexico, the vast majority of NWS flies remain in the south. A few cases have been found in northern Mexico. According to the USDA, the closest case to the US was approximately 70 miles south of Texas. On December 3, 2025, USDA officials reported a new case of NWS 120 miles south of the Texas border. At the time of this writing, all of the cases found in northern Mexico are no longer active.

In a recent audit of the NWS response in Mexico, the USDA reported that progress is being made in controlling NWS. Mexico is conducting outreach and educational programs for livestock producers and is developing emergency response and treatment protocols. They have expanded the workforce and increased surveillance for the parasite. The USDA states that more work is needed but remains committed to implementing the joint NWS action plan. NWS was eradicated from the US by using the Sterile Insect Technique (SIT). This program is the primary control measure being used in Mexico. Currently, the USDA Panama COPEG facility is producing 100 million sterile flies per week. These flies are being dispersed primarily in southern Mexico. However, a new dispersal facility was recently opened in Tampico, Mexico, which will allow for aerial dispersal in northern Mexico. Additionally, the USDA is investing $21 million to support Mexico’s renovation of a fruit fly facility to produce sterile NWS flies.

In the US, the USDA is currently constructing a dispersal facility at Moore Air Force Base in McAllen, Texas. This facility is expected to be operational in early 2026. In addition to the new dispersal facility, the USDA is planning the construction of a new NWS sterile fly production facility in the US.

When NWS was detected in Mexico in November 2024, the US did not have any Food and Drug Administration (FDA)-approved products for NWS control and prevention. Since then, the FDA has conditionally approved doramectin injection (Dectomax CA-1 injectable solution) for the control and prevention of NWS in cattle. On December 4, 2025, the FDA conditionally approved fluralaner (Exzolt Cattle-CA1) for prevention and treatment of larval infestation by NWS and treatment and control of cattle fever ticks. For cats and dogs, the FDA has conditionally approved lotilaner (Credelio) chewable tablets for the treatment of infestations caused by New World screwworm larvae (myiasis) in dogs and puppies, and lotilaner (Credelio CAT) chewable tablets for the treatment of infestations caused by the same larvae in cats and kittens.

With the start of winter, the spread of NWS into Oklahoma is unlikely. However, when spring arrives, the risk of NWS moving into Oklahoma may increase. Oklahoma livestock producers need to prepare for the possibility of an NWS outbreak. The USDA has recently launched a new website at screwworm.gov. This website contains valuable information such as clinical signs, the parasite’s life cycle, treatment and control options, and the latest updates on the current location of NWS. Livestock producers should visit this website frequently to stay up-to-date on the latest information. For additional information about NWS, livestock producers should consult with their local Oklahoma State University Cooperative Extension County Agriculture Educator.