Canine Whipworm Infection

What are whipworms?

Whipworms are intestinal parasites, about 1/4-inch long, that live in the cecum and colon of the dog. There they cause severe irritation to the lining of those organs, resulting in watery, bloody diarrhea, weight loss, and general debilitation. Whipworms are one of the most pathogenic (harmful) worms found in dogs, though they are quite rare in our area.

How did my dog get whipworms?

The life cycle is simple and stubbornly effective:

1. An infected dog passes microscopic eggs in its stool.
2. The eggs mature in the environment and become infective within 10 to 60 days.
3. Another dog (or the same one) swallows the eggs while sniffing, licking soil, or grooming its paws.
4. The larvae travel to the lower intestinal tract, mature, and begin laying eggs of their own.

The eggs are highly resistant to drying and heat, so they can remain viable in soil for years. A yard contaminated once can keep reinfecting dogs long after the original patient is treated — which is why reinfection, not treatment failure, is the usual reason whipworms come back.

How is whipworm infection diagnosed?

Whipworms are diagnosed by microscopic examination of the stool, but they are notoriously easy to miss: the females pass small numbers of eggs on an irregular schedule, so a single negative sample proves little. Multiple samples are often required.

Because of this, any dog with chronic or recurring diarrhea can reasonably be suspected of having whipworms, even after several negative stool examinations. It is accepted practice to treat on the assumption of infection — a good response to treatment is itself evidence that whipworms were present but escaping detection.

How are whipworms treated?

Several effective drugs are available. Two treatments are needed at a three- to four-week interval and, because environmental reinfection is such a problem, it is advisable to treat again every three to four months. The simpler long-term answer: after initial treatment, keep your dog on a monthly heartworm prevention product that also protects against whipworms. Widespread use of these products is exactly why whipworms have become uncommon.

Picking up stool promptly — at home and on walks — keeps eggs from seeding the soil in the first place.

Can I get whipworms from my dog?

No. Canine whipworms are not infectious to people. They can, however, infect other dogs sharing the same yard, so if one dog in the household is diagnosed, testing or treating the others is sensible.

See Feline Whipworm Infection