There are a multitude of diseases and parasites that might be encountered in a foreign environment. The disease-causing organisms that animals may harbor have the potential to produce serious consequences. For example, in 2003 an outbreak of monkeypox in people in the United States was traced to Gambian giant rats, which carried the virus from Africa. The rats infected prairie dogs intended for the pet market, and the prairie dogs, in turn, infected people.

When citizens return to the United States, their pets—which may be infected with foreign diseases or parasites—are also presented for re-entry into the country. Dogs, cats, and certain other pets are subject to measures designed to prevent the introduction and spread of rabies and other zoonotic diseases (diseases that humans can acquire from infected animals). If an animal is found to have one of these diseases, the case must be reported to the appropriate state authorities, who in turn, will notify the proper federal agencies.

Before returning to the US, pets must undergo a complete physical examination, including blood tests to detect the presence of certain parasites. Pets should be dipped in a medicated solution to remove any fleas, ticks, or mites that may have infested the animal while overseas. A thorough examination of the feces is necessary to look for worms and other parasites. If the animal is found to be infected, suitable medications to kill the specific parasites will be administered.

Upon arrival in the US, owners must schedule another physical examination by a veterinarian. This examination should also include blood tests. Pets should again be dipped in a medicated solution to resolve any infestations that may have occurred while the animal was in transit. There may be additional restrictions if you enter the Unites States through Puerto Rico, Guam, or Hawaii. Before returning through these ports, travelers should contact animal health inspectors for additional information.

The general re-entry requirement is that all dogs and cats imported into the US be visually inspected by US Public Health Service personnel. Only those animals that are free of any evidence of infectious disease may be admitted. Animals showing signs of illness such as emaciation, skin sores, disturbances of the nervous system, jaundice, or diarrhea, must be examined, tested, or treated at the owner's expense by a licensed veterinarian designated by the agency.

Entry/Re-entry of Cats

Cats are subject only to the general requirements for entry as stated above. Rabies vaccination of cats is not a federal requirement; however, some states require vaccination prior to entry.

Entry/Re-entry of Dogs

Regardless of their age, dogs may be admitted to the US without restriction if they appear healthy and have been in a rabies-free area for at least the 6 months immediately preceding arrival in the US or since birth. The US Public Health Service provides a current list of rabies-free areas.

Dogs arriving from countries other than those listed as rabies-free may be admitted to the US if they are 3 months of age or older, free of any evidence of infectious disease, and accompanied by a valid certificate of rabies vaccination. All 3 requirements must be met. Vaccination certificates must identify the dog, be signed by a licensed veterinarian, and specify the expiration date, which must be after the date of arrival. If the expiration date is not indicated on the certificate, the certificate is considered to be valid for only 1 year from the date of issue. Vaccination certificates should also specify the date of vaccination, which must be at least 30 days before the arrival date.

For dogs that are at least 3 months old, are subject to the rabies vaccination requirement, and appear to be healthy but do not have a valid rabies certificate as outlined above, the Centers for Disease Control and Prevention (CDC) Form 75.37 must be completed (generally at the point of entry) and submitted to the appropriate Quarantine Station for distribution. The form may be signed by the owner or agent.

The US Public Health Service may release the dog if the owner agrees to place it in confinement for 30 days immediately upon arrival at the destination and to have it vaccinated against rabies within 4 days. Confinement is defined as restriction of an animal to a building or other enclosure, in isolation from other animals and people except for contact necessary for its care. If the dog is allowed out of the enclosure, the owner must muzzle the dog and use a leash.

The CDC Form 75.37 must also be prepared if the dog is older than 3 months of age and has a certificate showing a vaccination administered less than 30 days before arrival. The owner is required to confine the dog for the remainder of the 30 days.

Finally, Form 75.37 must be prepared for dogs younger than 3 months of age at the time of entry or re-entry. The owner is required to confine the dog until it is 3 months of age and then have it immunized against rabies. The dog must then be confined for an additional 30 days. A vaccination certificate presented for a puppy less than 3 months of age cannot be accepted.

The USDA should be contacted for requirements specific to dogs used for working livestock to prevent importation of Echinococcus species, which are tapeworms associated with the development of hydatid cysts in livestock and humans.

Entry/Re-entry of Horses

The CDC does not regulate importation of horses into the US unless the horse is known to carry a disease transmissible to humans. The USDA requires quarantine of horses for various time periods (3 to 60 days), depending on which country the horse is entering from. The owner or transporter should contact the port veterinarian at one of the USDA Animal Import Centers to reserve space at the quarantine facility.

Last full review/revision July 2011 by Charles M. Hendrix, DVM, PhD