Don’t Get Screwed (Worm) When Leaving Costa Rica with Your Dog

Travellers with dogs take note! An additional requirement has been imposed on the export of dogs from Costa Rica to the USA, due to the emergence in Costa Rica of the New World Screwworm (NWS), a fly larva which causes large economical and tissue devastation to production animals as well as injury to other warm-blooded animals.

The first recent case of NWS was documented on the west coast of Costa Rica in July 2023, after not having had a case in this country since the 1990s. Since then, the larvae have been found in other regions of Costa Rica, leading to the emergency declaration earlier this year and to sterile flies being released in an effort to eradicate the population of the adult fly.

What this means to travellers with dogs is that in order to exit Costa Rica to the USA (even if your stay in the USA is only briefly for a connecting flight), every dog must be physically examined for any evidence of screwworm larvae, by a Costa Rican veterinarian within 5 days of export.

The ‘screwworm-free’ document must then be sent to SENASA (government office), stamped and returned to the clinic, and the dog exit the country before the 5 days has lapsed. This is in addition to the standard travel certificate noting general health, vaccination and deworming (the latter which is valid for 14 days).

The 5-day expiration of the screwworm document can make timing of a departing flight rather tricky, and is important to consider if it is after a weekend since the weekend counts as 2 days. For instance, for a flight departing on a Tuesday, the exam can be performed no sooner than the prior Thursday (day – 5). The stamped paperwork is likely ready to be picked up at the vet’s office on Friday or Monday, with Tuesday being day 5 and thus no room for a flight delay, or you would need to have your dog re-examined.

The New World Screwworm life cycle consists of the adult fly laying eggs on an open skin wound or orifice of a warm-blooded animal. The larvae hatch, feed on the wound and at a point of maturation drop to the ground and become adult flies. These skin wounds and larvae are what a veterinarian checks for on a dog.

Costa Rica joins several other countries currently trying to eradicate New World Screwworm. In addition to the NWS, when travelling internationally with a dog, two other infectious diseases to keep in mind that can affect import and/or export requirements for a given country include rabies and foot-and-mouth disease. It is thus always prudent to verify the current requirements for both exiting a country and entering another one, as these criteria may change.

Additional resources: Check the status of screwworm, foot-and-mouth and rabies disease (free of vs not free of) for various countries on this USDA website.