USDA halts U.S. pet dog and several other animal exports to Mexico amid multiple New World Screwworm cases

The U.S. Department of Agriculture (USDA) Animal Plant Health Inspection Service (APHIS) has halted the exportation of dogs and multiple other species to Mexico for an indeterminate period of time effective immediately. 

This comes after the USDA  announced on June 3, 2026, that Cochliomyia hominivorax or New World screwworm (NWS) larvae had been detected in the United States.

 A three-week-old calf in Zavala County, Texas, was found to have NWS larvae in its umbilical area. A second case of NWS was identified about five miles away from the first one in a one-month-old calf, as reported by the USDA on June 5. Two more cases, a calf in La Salle, Texas and a dog in Andrews County, Texas, have been confirmed today, and early reports suggest that the dog had been in Mexico. 

“Over the past week, USDA has identified and expeditiously confronted four confirmed detections of New World screwworm,” said Dudley Hoskins, Under Secretary for Marketing and Regulatory Programs. “While we address these instances that require immediate attention and continue to sample suspected cases, we are simultaneously working to eradicate the pest entirely.”  

Halting animal exports to Mexico 

Following the detection of NWS in the U.S., APHIS put out a notice that the following animals could no longer be exported to Mexico: 

• Cattle (slaughter and reproduction) 
• Wild ruminants (non-bovine) 
• Equine (slaughter, breeding/work, and sport/exhibition/transit) 
• Sheep and goats (slaughter and reproduction) 
• Pet dogs 
• Swine (reproduction) 
• Ferrets (commercial and pets) 
• Songbirds/ornamental birds/raptors (commercial and pets) 

According to the APHIS notice, importation of dogs from Mexico into the U.S. has not been halted completely, but strict requirements for screwworm freedom certification must be followed. This includes having dogs inspected for screwworm by an authorized veterinarian in Mexico within five days of shipment to the U.S. The veterinarian must certify that the dog is free from screwworm or that they have been treated for screwworm and held in quarantine until free from screwworm before traveling to the U.S.  

Other New World screwworm containment and eradication efforts 

Apart from the restrictions on the import and export of animals, the USDA and the state of Texas have taken additional actions to prevent spread and eradicate the parasite from the U.S. These actions include: 

• The formation of a unified Incident Command Team with the Texas Animal Health Commission  
• Deploying response personnel to the area where NWS was found and creating a 20 kilometer “infested zone” that will include quarantines, movement controls, and surveillance 
• Releasing sterile NWS flies in the infested area 
• Increased trapping of NWS flies along the U.S./Mexico border and just outside the dispersal area 
• Conducting surveillance for NWS in wildlife populations 
• Targeted outreach in the area to increase awareness of risk so that residents know how to reduce the risk of infestation, what to look for, and how to report any suspected cases.  

Resources for Veterinary Teams 

As new confirmed cases are reported, veterinary professionals have multiple resources they can consult to get guidance on the prevention, diagnosis, and treatment of NWS in animals.  

• USDA Confirmed detections of New World Screwworm dashboard 
• Companion Animal Parasite Council current NWS status and updates 
• Animal Health Contacts by state for reporting suspected cases of NWS 
• Dear Veterinarian letter from FDA on the use of FDA-Authorized Animal Drugs Against New World Screwworm Myiasis 

Important messaging for clients  

Veterinary professionals should remind their clients to check their pets and livestock for any wounds or signs of NWS and to seek treatment for wounds quickly. Clients should be reminded that NWS infestation in humans is also possible, although rare. Any humans who suspect they are infested should seek medical care immediately. 

If they ask, veterinary teams can also reassure clients that neither they nor their pets are at risk for NWS exposure via their food. “Screwworms do not infest meat, fruits, vegetables, or other food sources,” the USDA website clarified.  

“We need the partnership of animal owners across the region – please stay vigilant, check your animals closely, and report anything that looks suspicious,” Hoskins said. “Together, we can protect our livestock, our communities, and the health of animals nationwide.” 

Related Links: 

Texas issues disaster declaration as screwworm threat looms – AAHA 

Credelio Quattro-CA1 receives conditional approval from the FDA to treat New World Screwworm – AAHA 

FDA issues second Emergency Use Authorization for Credelio to treat New World screwworm, this time for felines – AAHA 

New World Screwworm: Risks to pets – AAHA 

First ever Emergency Use Authorization granted for veterinary drug Credelio (and what that means for veterinary medicine) – AAHA 

FDA issues first-ever Emergency Use Authorization for Credelio chewable tablets – AAHA 

Last updated on June 8 at 4:25 p.m. EST

Photo credit: © Liudmila Chernetska via Getty Images Plus

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