Whipworms in Dogs and Cats

Whipworm (Trichuris trichiura) of a dog in the institute for parasitology of the Ludwig-Maximilians-University Munich

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Whipworms are intestinal parasites that are relatively common in dogs but only occasionally seen in cats. The medical term for a whipworm infestation is "trichuriasis." They are named after the variety of Trichuris species that affect various host species. The parasite is often transmitted to dogs after they ingest infected matter (food or other matter).

How to Identify Whipworms

Whipworms are small worms, reaching a maximum size of 2 to 3 inches. They have a thin, whip-like front end and a thicker back end. The whipworms attach themselves to the walls of the large intestine, feeding on blood. Most infections are mild, especially in cats, but heavier whipworm infections can cause chronic health problems in dogs.

The Whipworm Life Cycle

Whipworms have a simple life cycle; their eggs are passed in their feces, and under ideal conditions, they become infective after about 2 to 4 weeks in the environment. The eggs are then ingested (e.g. during self-grooming, or eating things off the ground), and hatch in the small intestine.

Eventually, the larvae move to the large intestine, taking about 11 weeks to become mature and capable of producing more eggs which then pass to the environment. The eggs can survive for years in the environment. Whipworms are more common in older dogs than puppies, but they can infect dogs of any age.

Signs and Symptoms of Whipworms

In dogs with light infections, there are usually no symptoms. As infections get heavier, inflammation of the large intestine can result, and any of the following symptoms may appear:

  • Weight loss
  • Diarrhea
  • Mucus or blood in the stool
  • Anemia (pale gums, weakness) can be seen with chronic, heavy infections

Rarely, whipworm infections cause a syndrome similar to Addison's disease, with periodic episodes of weakness and electrolyte imbalance, though the mechanism of this effect is poorly understood. Also, it's important to note that the symptoms of the infection may be present before there is any visual evidence of the whipworm eggs. Cats usually have light infections and lack symptoms.

Diagnosis of Whipworms

The eggs of whipworms can be detected under the microscope in a check of a stool sample (the test process is called fecal flotation). Unlike roundworms and hookworms, female whipworms only produce eggs intermittently, so the eggs can be difficult to catch on fecal tests. Repeated tests may be necessary, and if a whipworm infection is suspected it is common to treat for whipworms even if eggs aren't found.

Treating Whipworms

There are a number of medications that can be used to treat whipworms, and your vet can help you pick the one right for your dog. Whipworms are often resistant to some common dewormers, so the treatment may be a prescription that is new to you. Repeated treatments are usually recommended for best results (e.g., after 3 weeks and 3 months). If your dog or cat is already taking a prescription heartworm medication, make sure you inform your veterinarian. They will need to align medications before starting on a course of a separate whipworm dewormer.

Since the eggs survive for so long, the potential for re-infections from eggs that are left in the intestinal environment is significant and quite high. Your vet may recommend a monthly parasite preventative that is effective for whipworms to prevent whipworm infections on an ongoing basis. It's important to promptly and sanitarily remove pet waste to help prevent infections with whipworms.

If your dog has been diagnosed with whipworms, take care to clean any surfaces that may be infected. Use household bleach and other disinfectant cleaners. If your dog frequently defecates in a certain area in your yard, it may be beneficial to replace the gravel, woodchips, or other material that could be infected and is hard to clean.

People and Dog Whipworms

There have been rare and controversial reports of people being infected with dog whipworms. However, animal whipworms are not considered a significant human health risk (humans do have their very own species of whipworm, though).

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.