Screwworm Certificate for Mexico: What US Pet Owners Need Now
Last updated: September 2026. By Mia Sgarlato, founder of Pet Passport Club
If you're driving or flying to Mexico with your dog this fall, the paperwork changed on you in August. Mexico now requires a New World screwworm certificate for every pet dog coming in from the US, and it has a five-day shelf life. Miss the window and you're either turning around at the border or getting denied boarding at the airport.
Short answer: As of August 3, 2026, every pet dog entering Mexico from the US needs an NWS Inspection Certificate signed by a USDA-accredited vet no more than 5 days before arrival. No USDA endorsement needed. Cats are exempt. On the way home, your dog needs a separate screwworm freedom certificate from an authorized vet in Mexico, also within 5 days.
Who this is for: This post is for US pet owners taking a dog or cat into Mexico by land or air, whether it's a weekend in Baja or a full relocation to Puerto Vallarta.
Why Mexico Now Requires a Screwworm Certificate for Dogs
New World screwworm is a fly whose larvae feed on the living tissue of warm-blooded animals. It was eradicated from the US in the 1960s, but it's been working its way north through Central America and Mexico for years. On June 3, 2026, USDA confirmed the first US case in decades, in a calf in Zavala County, Texas.
Mexico responded fast. It shut down most US livestock imports in June and, for about a week, pet dogs were caught up in the ban too. USDA clarified on June 11 that dogs could cross again under the old rules. Then on August 3, Mexico's animal health agency, SENASICA, made the current rule permanent: pet dogs and pet birds need a screwworm inspection before entry.
As of early September 2026, there have been 48 confirmed US cases across Texas and New Mexico, including three dogs. That's why the rule isn't going away anytime soon.
What the Mexico Screwworm Certificate Actually Is
The document is called the NWS Inspection Certificate for Pet Dogs Moving (Exporting) from the United States to Mexico. It's a one-page USDA form your vet fills out after a hands-on exam.
Here's what matters about it:
Who signs it: a USDA-accredited veterinarian. Not every vet is accredited, so ask when you book.
When it's issued: no more than 5 days before your dog arrives in Mexico. The clock runs to arrival, not departure, which helps if your flight slips a day.
Endorsement: none. Unlike the EU health certificate, this one doesn't go to USDA for a stamp. Your vet signs it and you're done.
What the vet checks: open wounds, tick bites, umbilical scars, and mucous membranes for any sign of larvae or infestation.
The certificate is the easy part. The five-day window is what trips people up. If you're driving from Denver to Cabo over a week, the exam has to happen in the last five days before you cross, not the day you leave home.
Do Cats Need a Screwworm Certificate for Mexico?
No. Mexico's rule covers pet dogs and pet birds only. Cats still enter with no health certificate at all, the way they have for years. SENASICA will physically inspect your cat at the port of entry, but there's nothing to fill out ahead of time.
Pet birds are a different story: they need the NWS Inspection Addendum plus a USDA-endorsed health certificate, both within 5 days of arrival. If you're flying with a parrot, budget extra time for the endorsement.
What Happens at The Mexican Border or Airport
Every dog and cat gets a physical inspection at the OISA (SENASICA's inspection office) on arrival. The officer is checking for four things:
No signs of infectious or contagious disease
No ectoparasites (fleas, ticks, fly larvae)
No fresh or healing wounds
A valid NWS certificate (dogs only)
Your carrier has to be clean, too. Bedding, blankets, toys, and treats get confiscated. Bring one day's worth of factory-sealed food with the ingredients visible on the label and nothing else in the crate.
If they find a tick or a wound, your pet goes into SENASICA custody. You'll be told to hire a licensed Mexican vet, at your own expense, to treat on the spot. If ticks are found, they get sent to a lab and your dog stays put until results confirm it's not an exotic species. That can take days.
Airports enforce all of this every time. Land borders are inconsistent, and I hear from clients who got waved through without anyone looking at the dog. Don't plan around that. The one time you're pulled for a secondary check is the one time it matters.
If you'd rather not gamble on timing and paperwork for a trip that's supposed to be fun, our Mexico guide walks through the full process step by step.
Getting Your Dog Back Into the US From Mexico
This is the part most people don't know about, and it's been true since November 2024, well before the Texas outbreak. USDA considers Mexico a screwworm-affected country. That means every dog entering the US from Mexico, including your US dog coming home from vacation, needs a screwworm freedom certificate.
The return certificate has to:
Be signed by an official Mexican government veterinarian, or by a clinical vet authorized under Mexico's MVRA program (USDA links the directory)
Confirm your dog was inspected within 5 days before entering the US
State the dog is free of screwworm, or was treated until free
On top of that, the standard CDC rules still apply: your dog must be at least 6 months old, microchipped, healthy on arrival, and you need a CDC Dog Import Form receipt [link to: CDC Dog Import Form page]. The form is free and takes about five minutes.
So plan on two vet visits, not one. A US-accredited vet within 5 days of arriving in Mexico, and an MVRA-authorized vet in Mexico within 5 days of coming home. If you're doing a long weekend, that's tight, so book the Mexican vet before you leave the US.
One thing I'm watching: for cats, USDA's screwworm rule is written for dogs, and USDA's Mexico page says nothing changed for cats. Cats can still be inspected by CBP on the way back, so bring your rabies certificate and keep the carrier spotless.
Mexico Screwworm Certificate Timeline
Here's the whole trip laid out so you can see where the two five-day windows land.
The takeaway: both certificates live inside 5-day windows, and the return one has to be issued by a vet in Mexico, not your vet at home.
Common mistakes with the Screwworm Certificate for Mexico
Counting from departure instead of arrival. The window ends when you land or cross, so a road trip with stops can eat your five days.
Using a non-accredited vet. A regular wellness exam from a vet who isn't USDA-accredited doesn't count. Ask before you book.
Forgetting the return leg. Nobody tells you about the Mexican-side certificate until you're at the port of entry without one.
Packing the crate like a bed. Blankets and toys get tossed at inspection. Save the comfort items for after you clear.
Skipping a wound check. A healing scrape from the dog park is enough for SENASICA to hold your dog. Look your dog over the morning you travel.
Getting the timing right on both ends is the whole game here. If you want a second set of eyes on your plan before you go, a consult call is the fastest way to do it.
Screwworm Certificate for Mexico FAQ
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Yes. Since August 3, 2026, every pet dog entering Mexico from the US needs an NWS Inspection Certificate signed by a USDA-accredited vet within 5 days of arrival.
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No. Your accredited vet signs it and that's it. This is different from the EU health certificate, which does require APHIS endorsement.
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No. Cats are exempt from the NWS certificate and don't need a health certificate for Mexico at all. They're still physically inspected on arrival.
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It's a standard vet exam plus the form, so expect to pay your vet's office visit fee. Prices vary by clinic. There's no USDA fee since there's no endorsement.
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Yes. Any dog entering the US from Mexico needs a screwworm freedom certificate from an official or MVRA-authorized Mexican vet, issued within 5 days of entry, plus the CDC Dog Import Form.
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Maggots or white egg masses in or around a wound, the ears, nose, eyes, or mouth; a foul smell from a wound; and a dog who suddenly seems irritable, withdrawn, or off their food. Any of those means a vet visit the same day.
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Yes. The certificate applies at land borders and airports alike. Land crossings are enforced less consistently, but you should carry the paperwork every time.
Want to bring your dog to mexico?
Mexico used to be one of the easiest countries to take a dog to. It still is, as long as you respect the two five-day windows. If you'd rather hand the coordination to someone who does this every week, our Co-Pilot Concierge service manages both vet appointments and the timing for you, and the Mexico guide is there if you're going the DIY route.
Questions? We're a message or consult call away.
— Mia + Poppy
