Eight new cases of New World screwworm (NWS) confirmed in the Mexican state of Tamaulipas are raising renewed concerns for cattle producers across the southern United States. The latest detections bring the total number of confirmed cases in Tamaulipas to 11 since late December, placing the pest roughly 215 miles from the Texas border.
Although no cases have been detected in the United States, officials warn the rapid increase in infections suggests the possibility of an established screwworm fly population in northeastern Mexico.
Texas Department of Agriculture (TDA) confirmed that Mexican animal health authorities have not reported any recent movement of the affected cattle outside Tamaulipas. That detail has heightened concern among U.S. officials that the pest may be spreading naturally, rather than through livestock transport.
Officials Urge Producers to Stay Alert
Texas Agriculture Commissioner Sid Miller urged producers to take immediate precautions, particularly those operating near the Texas–Mexico border.
“When you’re seeing this many cases in such a short period of time, it points to the possibility of established screwworm populations,” Miller said. “Texas producers need to stay informed, stay vigilant, and prepare now. We cannot afford to let our guard down.”
New World screwworm larvae infest open wounds, feeding on living tissue and causing severe injury or death if left untreated. Officials emphasize that daily livestock observation is critical for early detection.
Producers are advised to:
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Inspect cattle regularly, especially young animals
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Treat and monitor all wounds promptly
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Pay close attention to navels on newborn calves
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Isolate and report anything suspicious immediately
Surveillance and Trapping Expanded Along the Border
To strengthen early detection efforts, TDA has activated a comprehensive NWS trapping plan across high-risk areas along the Texas–Mexico border. Traps have been placed strategically at:
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Ports of entry
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Livestock export facilities
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Locations with elevated risk of pest introduction or animal movement
TDA inspectors monitor traps daily, with samples quickly analyzed in coordination with federal partners, including the United States Department of Agriculture.
“If the screwworm crosses into Texas, we will know,” Miller said. “Our surveillance is active and aggressive, but producer awareness is the first line of defense.”
Border Status and Market Implications
The U.S. border has remained closed to imports of live cattle from Mexico for much of the past year. While some industry observers had anticipated reopening discussions, continued NWS detections in Tamaulipas have introduced further uncertainty.
Analysts note that repeated detections reduce the likelihood of near-term cattle movement from Mexico, even if border conditions eventually change. However, there is currently no indication of a large backlog of cattle waiting to cross, and supply impacts are expected to remain limited in the short term.
Identification and Reporting Remain Key
Adult New World screwworm flies resemble houseflies but can be identified by:
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Metallic blue or green bodies
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Orange eyes
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Three dark stripes along the back
Producers who suspect NWS should contact a veterinarian immediately. Symptoms that warrant reporting include:
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Irritated or agitated behavior
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Head shaking
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A foul odor from wounds
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Visible fly larvae (maggots)
Additional information and reporting guidance are available through USDA’s official NWS resource at screwworm.gov.
While the United States remains free of New World screwworm, officials stress that early detection, aggressive surveillance, and producer vigilance will be essential to keeping it that way.
