Whipworm Overview

Whipworms are small, parasitic roundworms that have a tail shaped like a whip and live in the small intestines of dogs and other mammals. Whipworms attach themselves to the wall of the large intestine and feed off the blood of the dog. Female whipworms can grow to three inches in length and produce up to 2,000 eggs per day! In contrast to parasites such as heartworms, that hatch in one part of the body and migrate to another, whipworms hatch and live in the intestine. Canine whipworms are found throughout the U.S., but are most common in warm and humid climates.

Spreading Whipworm

Whipworm eggs are present in the dog waste of infected dogs. Dogs are infected with whipworm when they consume whipworm eggs. Dogs most frequently ingest the whipworm eggs when cleaning their paws or drinking infected water. Different whipworm species affect different animals. This means that whipworms that evolved to live in dogs cannot infect people.

Symptoms of Whipworm Infection

Dogs infected with whipworms generally do not display many symptoms. The most common visible signs that your dog may have a whipworm infection include:

  • Bloody Stool
  • Weight Loss
  • Dehydration
  • Anemia

While rare, the severe dehydration and anemia caused by acute whipworm infestations may result in the death of the infected animal. Young dogs and puppies are the most susceptible to dangerous infections.

Diagnosis of Whipworm

Diagnosis of whipworm infestation is performed by using a fecal coliform test to look for whipworm eggs. To perform this test a small amount of dog waste is suspended in a solution. The solution has a density such that the dog poop sinks, while the whipworm eggs float to the surface. This test is accurate when whipworm eggs are present in the waste. However, because, not all tested waste will contain eggs, it is not 100% accurate.

Treating Whipworm Infections

Like many parasites, whipworm eggs are extremely tough and difficult to kill. In fact, whipworm eggs can live up to five years in infected soil! This means that even if your dog is free of the parasite, he will likely re-infect himself if his yard or the area he regularly walks contains whipworm eggs.

The long lifespan of the eggs and subsequent and predictable re-infection means that one-time whipworm treatments will not cure your dog permanently. Initial treatment will involve giving your dog doses of a de-worming agent such as Milbemycin Oxime. Milbemycin Oxime works by interfering with the nerve impulses of whipworms. At least two treatments are given approximately 3 weeks apart. This is because Milbemycin Oxime kills the adult worms but does not kill the larvae. During the first and second treatments larvae will mature into the more vulnerable adults. A final treatment kills these adults. After this treatment there are no worms left.

Preventing Whipworm Infections

The most reliable method of preventing serious whipworm infections is to give your dog a monthly dose of a drug that contains the oral medication Milbemycin Oxime. This medication DOES NOT kill the whipworm eggs; instead it kills the adult worms. If the treatment is given monthly, the worms will not establish themselves in the intestine and your dog will not experience negative effects of the infection.

Long-term control of whipworms in the environment requires that all dog waste be picked up and disposed of promptly. Dogs should also receive a regular whipworm preventative such as Interceptor that contains Milbemycin Oxime.


  • Thorough background information on whipworms from Great Lakes Border Collie Rescue.
  • Explanation of how Novartis’s INTERCEPTOR product works (the active ingredient is milbemycin oxime).
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