Federal animal health officials lifted movement restrictions on livestock in part of New Mexico on Aug. 30, the first time any area of the United States has come out from under a screwworm control zone since the outbreak began in June.
The New World screwworm is a fly whose larvae burrow into the living tissue of warm-blooded animals. An infestation can kill an untreated adult cow in about two weeks. The United States eradicated the pest in 1966 and has spent decades keeping it pushed south; it has been moving back north through Mexico for two years.
When a case is confirmed, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service draws an infested zone around it and requires livestock and pets leaving that area to be inspected before they move. New Mexico had one such zone, drawn around a single case in a dog confirmed in Lea County on June 7.
“No additional cases have been detected since the initial confirmation on June 7,” the agency said in its announcement. “The infested zone is officially released as of today, August 30.” The agency said it acted on the recommendation of New Mexico’s state veterinarian, Dr. Samantha Holeck, and the New Mexico Livestock Board.
The practical effect is immediate. Lifting the zone “removes the NWS-related requirements on the domestic movement of livestock and pets from that area, allowing producers and owners to resume normal intrastate and interstate movement without inspection for NWS,” the agency said.
Texas is in a different position. Every one of the 47 animal cases confirmed in the United States since the first detection on June 3 has been in a domestic animal, and all but the New Mexico dog have been in Texas, according to the agency’s confirmed-detections dashboard, read Aug. 31. Two remain active, both in Val Verde County on the Rio Grande — sheep confirmed Aug. 16 and goats confirmed Aug. 25. Earlier cases in Terrell, Pecos and Brewster counties have been closed out.
Two numbers have not moved at all, and they are the ones that would signal the infestation had established itself here rather than arriving with animals: cases in wildlife and feral animals stand at zero, and detections in the fly traps set across the region stand at zero. There have been no human cases.
Texas moved the other direction in the same week. The Texas Animal Health Commission’s executive director issued an order on Aug. 24 imposing new requirements on cattle of Mexican origin that enter the country through a port outside Texas and are then brought here. Those animals now need official electronic identification, an electronic health certificate and an entry permit. “New World screwworm (NWS) continues to expand in Mexico,” the commission said in announcing the order.
The scale of that expansion is visible in the federal government’s own tracking. The agency publishes a running list of confirmed Mexican cases within 100 miles of the U.S. border and updates it each business day; that list stood at 395 entries as of Aug. 31, with recent additions in Nuevo León and Coahuila.
Ports of entry have been reopening cautiously. Douglas, Arizona resumed accepting Mexican cattle on Aug. 24. The agency’s current status page, last updated Aug. 26, describes reopening at Santa Teresa and Columbus, New Mexico only as something it “will then consider.” Texas ports remain closed to Mexican cattle.
The agency also said on Aug. 26 that it will begin reviewing its response plan on a quarterly schedule, with the first stakeholder meeting set for Sept. 9.