by Krista Halling DVM DACVS
Effective August 3, 2026, all dogs entering Mexico from the United States will need to show a New World Screwworm-Free Certificate. This new regulation is for all dogs arriving from the US including those doing a layover in a US airport.
This certificate needs to be completed and signed by a USDA-accredited veterinarian in the United Stated, within 5 days of entering Mexico. This is in addition to existing dog import requirements.
This means that if you and your dog are travelling to Mexico via an airport in the US (e.g. Toronto-Houston, Houston-Cancun), you will likely need to arrange an appointment with a USDA veterinarian in Houston to obtain a screwworm-free certificate, within 5 days of your flight to Mexico.
New World screwworm (Cochliomyia hominivorax) is a parasitic fly that lays its eggs in wounds of warm-blooded animals, including dogs. Once hatched, the larvae (maggots) burrow into the wound, causing further tissue damage, which in turn attracts more flies. Infestations can have devastating health and economic implications — especially for farm animals. This is why border authorities are taking prevention seriously.
The NWS is already present in many countries including the Caribbean, Mexico, and now has been identified in the Southern US. Canada remains NWS-free as our climate is likely too cold for it. The risks from vacationing domestic dogs are by maggots inadvertently being imported via the wound of a travelling animal.
The new regulation is an attempt to mitigate the New World Screwworm from entering Mexico from the US. Note that a similar regulation is in effect for dogs entering the US from Mexico. So if you and your dog are returning to the US, or travelling home via the US, from Mexico, you will need to obtain a government-stamped screwworm-free certificate from a veterinarian in Mexico.
For updates and more information, go to the USDA’s animal import page.
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