Mexico Faces New World Screwworm Outbreak

On January 2, 2026, Mexican authorities reported a second case of the New World screwworm parasite within two days, as efforts to contain the outbreak continue. The latest case involved a goat in the State of Mexico, which borders Mexico City. The Ministry of Agriculture confirmed that 20 other animals at the site tested negative and received preventive treatment. This follows a December 31 report of a case in a six-day-old calf in Tamaulipas, which was the only positive case at that location.

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Since November 2024, Mexico has documented a total of 13,106 screwworm cases, with 671 currently active. The southern border state of Chiapas has reported the highest number of cases, followed by Oaxaca, Veracruz, and Yucatan. The New World screwworm is a parasitic fly that lays eggs in open wounds, with larvae that burrow into the flesh of animals, potentially leading to death if untreated.

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The outbreak has significant implications for the livestock and beef industries in both Mexico and the United States. Since May 2025, the U.S. has largely closed its southern border to Mexican livestock to prevent the spread of the parasite. U.S. officials assert that the pest has not yet crossed into the U.S., but the potential economic damage is substantial, with estimates from the U.S. Department of Agriculture suggesting a threat of $1.8 billion to Texas' economy alone.

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Mexican authorities are actively working to control the outbreak and have implemented measures to treat affected animals and prevent further spread. The Ministry of Agriculture's ongoing monitoring and treatment efforts are crucial in addressing the situation.

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Some critics argue that the response to the outbreak has been slow and insufficient, raising concerns about the effectiveness of containment measures. The livestock industry is particularly anxious about the long-term effects of the outbreak on trade and animal health.

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While the reported cases indicate a growing concern, there is a lack of detailed information regarding the specific measures being taken to combat the outbreak and the effectiveness of those measures. Additionally, the exact number of livestock affected and the geographic spread of the parasite remain unclear.

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As the situation develops, both nations remain vigilant in monitoring and addressing the challenges posed by the New World screwworm outbreak.

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