The U.S. Department of Agriculture (USDA) is currently battling an outbreak of New World screwworm (NWS) following the detection of five cases in Texas and New Mexico within a single week. While no cases have been confirmed in California, the parasite—which burrows into the flesh of livestock and can be fatal if left untreated—has triggered heightened surveillance and concern among ranchers.
Why are ranchers concerned about a potential NWS outbreak?
Ranchers are wary because the New World screwworm is a destructive pest that can cause significant losses to the livestock industry. According to UC Davis Veterinary Medicine, adult NWS flies are slightly larger than houseflies and lay eggs in animal wounds or body openings. Larvae hatch within 12 to 24 hours, utilizing sharp mouth hooks to burrow deep into the flesh, creating painful, potentially fatal wounds.
Todd Snider, president of the Kern County Farm Bureau, noted that California’s livestock industry has been vocal about the necessity for monitoring and prevention efforts along the border. He expressed encouragement that the USDA has increased its attention to the state over the past year. In response, some producers are taking individual action; Jack Lavers, a rancher in Glennville, told the Bakersfield Californian that he plans to be more diligent in treating animal wounds and will incorporate garlic into his feed to deter flies.
How is the USDA managing the current infestation?
The USDA is actively working to contain the parasite through surveillance and the release of sterile flies. According to Dudley Hoskins, under secretary for marketing and regulatory programs, the department is sampling suspected cases while simultaneously working to eradicate the pest entirely. In Texas, where three calves and a goat tested positive for NWS, the USDA has initiated a plan to release 4 million sterile flies per week to curb the infestation.
The strategy of using sterile flies is a proven method, having been used to eradicate NWS in the U.S. around the 1960s. However, supply chain constraints remain a challenge. Currently, Panama is the only country in North America producing sterile NWS flies. To bolster capacity, the USDA announced in April that it invested $21 million to convert a former fruit fly facility in Metapa, Mexico, into an NWS sterile fly facility. This site is expected to produce an additional 60 million to 100 million sterile flies by this summer.
What is the history of NWS in the United States?
While NWS was historically eradicated in the U.S. decades ago, the parasite has shown signs of a slow return in recent years. The Centers for Disease Control (CDC) reports that NWS cases began appearing in Mexico and Central America around 2023, and the parasite was detected in Texas that same year. According to Agri-Pulse, these recent detections follow a period where the Trump administration cut $250 million in funding for projects under the Global Health Security Program, which included initiatives to monitor and contain the screwworm.
Frequently Asked Questions
What are the symptoms of NWS in animals?
The primary indicators are non-healing wounds or the presence of maggots in body openings, including the nose, ears, or genitalia. Owners should inspect animals for these signs regularly.
Is New World screwworm fatal?
Yes, if left untreated, the larvae can burrow deep into the flesh, causing severe, painful wounds that may lead to death. Prompt veterinary attention is critical.
Are there cases in California?
As of the most recent reports, there have been no confirmed cases of NWS in California. The USDA is maintaining increased surveillance in the region as a preventative measure.
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