Whipworms are a common and significant cause of most intestinal illness is dogs. While whipworms in dogs are reported worldwide, dogs that live in the eastern half of the United States appear to be at higher risk. According to the Companion Animal Parasite Council (CAPC), over 14% of shelter dogs in the U.S. test positive for whipworms. The good news is that whipworm treatment in dogs is fairly straightforward. Whipworms are also easily prevented, and they aren't considered a zoonotic disease (or passed between animals and humans). Read on to learn more about whipworms and how they can affect your dog.

What Are Whipworms in Dogs?

Whipworms, also known by their scientific name Trichuris vulpis, are intestinal parasites that live, reproduce and cause problems in the colon. The type of whipworms found in dogs are also seen in coyotes and foxes, but whipworms in dogs are not considered to be contagious to humans or cats.

These parasites are called whipworms because of their whip-like shape — thicker on one end and thinner on the other. They vary in length but can be as long as a matchstick. Dogs can only be infected with whipworms one way and that is by accidentally ingesting infectious eggs from the environment. Once ingested, the egg hatches and parasitic larvae develop in the small intestine, then migrate to the colon, where the parasite attaches itself to the lining of the intestine and feeds on it as well as blood.

Adult whipworms lay eggs that are shed in feces and contaminate the environment. Whipworm eggs are extremely tough, have a thick shell and can persist even in hot, dried-out dirt for years — waiting for an opportunity to infect a host. Furthermore, it takes about three months for eggs to show up in feces after a dog accidentally ingests a whipworm egg, according to Today's Veterinary Practice, so a dog may be infected with whipworms without your knowledge.

Signs of Whipworms in Dogs

Because of the way the worm feeds off its host, whipworms cause damage to the lining of the intestine, which can result in:

• Bloody, mucus-y diarrhea
• Weight loss
• Dehydration

If you suspect your dog has whipworms, schedule an appointment with your veterinarian as soon as possible. Bring a fresh fecal sample in a sealed container with you to the appointment as well.

Diagnosing Whipworms in Dogs

Whipworms are usually diagnosed with a combination of history from you (how is your dog doing, is your dog on heartworm prevention, etc.), physical examination findings and special fecal tests to look for parasitic eggs.

Whipworm eggs are relatively big and heavy in comparison to other intestinal parasites. They're most easily detected with a fecal centrifugation, where the sample is spun at high speeds and then placed under a microscope to look for eggs. The tricky thing about whipworms is that they take a long time to lay eggs after a dog is infected, and they only shed eggs intermittently. Sometimes, repeated fecal tests are required if the vet suspects a whipworm infestation but few or no eggs are seen under the microscope.

Puppies are at a higher risk for whipworm infections, and the CAPC recommends puppies be tested for all intestinal parasites at least four times during the first year of life. Biannual fecal tests are recommended for dogs older than one year.