Whipworms are intestinal parasites. They parasitize the lower intestine (cecum and colon) and cause signs related to intestinal irritation. Infection with whipworms can be significant because they are one of the more pathogenic intestinal parasites found in dogs and cats.

They are small, about 1/4″ (45 to 75 mm) long, and have a characteristic “whip” or “lash” at one end.
After the worm burrows into the intestine, it is this “whip” that causes damage to the lining of the
bowel. The tip of the “lash” is able to slash and shred tissue. The worm then feeds on the blood and
damaged lining of the intestine.

Contributing Factors

An animal is more likely to become infected whipworms if it resides in an environment contaminated
with whipworm eggs. The eggs are very resistant to destruction and can remain viable (infective) in
the soil for months or even years.


The whipworm is found throughout North America, although it is most common in the eastern and southern United States. In other countries, different species of whipworms can exist.


Whipworms pass microscopic eggs in the stool, which must be swallowed to infect the dog or cat. Once the eggs mature into adult worms, eggs are passed in the dog’s stool and can infect another pet.

Clinical Signs

The most significant clinical sign of whipworm infection is bloody and/or mucoid (mucous) stool. Overt diarrhea may or may not be present. The animal may exhibit pain during defecation and attempt frequent bowel movements. In animals with chronic whipworm infection, debilitation may develop and the pet will lose weight and possibly become anemic.


Whipworm infection is diagnosed by finding the characteristic eggs during a microscopic examination of the stool. Several samples may be required because these parasites pass small numbers of eggs on an irregular basis. Any animal with chronic diarrhea can be reasonably suspected to have whipworms, regardless of several negative stool examinations. It is advisable to treat for whipworms based on assumption of infection when chronic or refractory diarrhea is present. Response to treatment is an indication that whipworms were present but could not be detected on fecal examination.

Treatment and Prevention

Several available drugs are very effective against whipworms. Two treatments are needed at a 3-4 week interval. We recommend Drontal Plus or Panacur for treatment of whipworms. Since reinfection is such a problem, it is advisable to treat again every 3-4 months or to put the dog on a heartworm preventive product that also prevents whipworms. Whipworms are not nearly as common now because of widespread use of the heartworm preventives that help to control whipworms.


The prognosis for full recovery is good if the entire course of treatment is completed. In contaminated environments, reinfection may occur.

Transmission to Humans

There is a very small risk of human infection by whipworms. Eggs of this parasite have occasionally been observed in stool samples of humans. These should be noted as rare events, however. The overall health risk to humans is considered very small.