MEXICO CITY (RFD-TV) — A new livestock checkpoint in Montemorelos, Nuevo León, stopped a calf carrying New World screwworm—and the larvae were already dead.
Under Mexico’s reinforced rules, all animals receive a double treatment (ivermectin plus a larvicidal bath). Inspectors treated and checked the full load of 85 head and found no other cases.
This most recent case was discovered 170 miles south of the border, in a shipment of more than 80 animals. Mexico’s ag ministry says this was the second confirmation in two weeks.
The infected animal was a calf, but no other livestock was infected with screwworm. Mexican officials say that when the pest was discovered, it was already dead, primarily due to mandatory treatments in Mexico.
A detection was reported last month, located closer to the US, just 70 miles south of the Texas border. Officials said this incident is separate from the Sept. 20 detection in Sabinas Hidalgo, which was officially declared inactive on Oct. 5 after tracing, wound care for thousands of animals, trapping, and sterile-fly releases.
On the U.S. side, regulators have conditionally approved Dectomax-CA1 (doramectin injection) for the prevention and treatment of screwworm in cattle, with 21 days of reinfestation protection. The move is meant to get producers a tool now while full-effectiveness data are finalized. Label restrictions and withdrawal times still apply, and veterinarians are urging the targeted use of these products as part of an integrated parasite control plan to help prevent animals from developing resistance to treatments.
Agriculture Secretary Brooke Rollins says she has been in touch with Mexican officials. As a result of this latest detection, the USDA will send crews to the region to deploy traps and release more sterile flies. Rollins says the USDA’s number one goal remains keeping the U.S. herd safe and secure.
