Federal agriculture officials have confirmed two additional cases of the New World screwworm in Texas, deepening concern among livestock producers and regulators that a parasite once eradicated from the United States may be gaining a foothold again in parts of the country.
The U.S. Department of Agriculture announced on Monday that the new infections were detected in a calf and a dog located in separate Texas counties, hundreds of miles apart in La Salle and Andrews counties. The findings bring the total number of confirmed cases in the state to four, following earlier detections in young calves reported last week.
The emergence of multiple cases in such a short period has intensified concern within the agricultural sector, which views the screwworm as one of the most destructive livestock pests in history. Before it was eliminated from the United States in the 1960s, the parasite regularly inflicted severe losses on cattle ranchers during warmer months, spreading rapidly through livestock populations and wildlife.
Unlike typical flies that feed on decaying organic matter, the New World screwworm is a parasitic species whose larvae feed on living tissue. Female flies lay their eggs in open wounds or mucous membranes of warm-blooded animals, including cattle, pets, wildlife and, in rare cases, humans. Once hatched, the larvae burrow into living flesh, causing serious injury and potentially fatal infections if left untreated.
The U.S. Department of Agriculture said it is responding urgently to contain the situation while continuing surveillance and sampling efforts across affected regions. Officials emphasized that eradication remains the ultimate goal even as they work to manage newly identified cases.
Dudley Hoskins, the department’s undersecretary for marketing and regulatory programs, said in a statement that authorities are balancing immediate containment efforts with longer-term eradication strategies. He stressed that the agency is continuing to investigate suspected cases while reinforcing its broader control measures.
The recent detections come amid heightened vigilance by U.S. agriculture officials and the cattle industry, which has been on alert since screwworm was detected in Mexico in late 2024. That discovery marked a troubling development after decades in which the pest had been largely confined to regions south of Panama due to sustained eradication campaigns.
For American livestock producers, the risk posed by a potential resurgence is significant. The cattle industry, a cornerstone of U.S. agriculture, remains highly vulnerable to parasites that can spread quickly across herds and geographic regions, particularly in warmer climates where flies are most active.
The federal government has long relied on a highly specialized eradication strategy to combat screwworm outbreaks. Central to that approach is the sterile insect technique, a biological control method in which large numbers of sterilized male flies are released into the wild population. Because female screwworm flies typically mate only once during their lifespan, mating with sterile males results in no offspring, gradually reducing the population over time.
This method was instrumental in eliminating screwworm from the United States in the mid-20th century and remains the primary tool for preventing its return. Agricultural officials have indicated that they intend to scale up production of sterile flies, including through facilities located outside the United States, while also constructing a new production facility in Texas to strengthen domestic capacity.
The urgency of the response reflects both the biological resilience of the pest and the economic stakes involved. Even isolated outbreaks can spread quickly if not contained, particularly given the movement of livestock, wildlife and domestic animals across large rural areas.
Federal officials have emphasized that early detection is critical to preventing a wider infestation. Surveillance programs have been expanded in affected regions, and veterinarians and ranchers have been urged to report suspicious wounds or infestations in animals.
The latest cases, identified in both a calf and a domestic dog, underscore the broad range of animals that can be affected. While cattle remain the primary concern due to their economic importance, the parasite does not discriminate between species, and infections in pets or wildlife can serve as indicators of wider environmental spread.
The Department of Agriculture has scheduled high-level briefings to assess the situation, including an update for Agriculture Secretary Brooke Rollins at the U.S. Livestock Insects Research Laboratory in Kerrville, Texas. The facility plays a central role in research on insect-borne threats to livestock and is expected to inform ongoing containment and eradication strategies.
Officials have not yet indicated whether movement restrictions or quarantine measures will be imposed in affected areas, but they have made clear that the situation remains under active review. For now, the focus remains on identifying additional cases, preventing further spread and reinforcing control measures that have historically proven effective against the pest.
The screwworm’s reappearance in Texas has revived long-standing concerns within the agricultural community about the fragility of eradication efforts. Although the United States successfully eliminated the parasite more than half a century ago, its continued presence in parts of Latin America has always carried the risk of reintroduction.
That risk has now become more immediate.
As federal and state officials intensify their response, the broader question facing the livestock industry is whether existing containment systems can again push the pest back beyond U.S. borders, or whether new environmental and logistical challenges will complicate efforts to replicate one of the most significant agricultural eradication successes in modern history.
For ranchers and veterinarians across Texas and beyond, the coming weeks will be critical in determining whether the latest detections remain isolated incidents or the beginning of a broader resurgence of a parasite that once defined the summer season for American cattle operations.
