This worm is one of the "big four" intestinal parasites with which our canine friends must contend: roundworms, tapeworms, hookworms, and whipworms. The whipworm of dogs (Trichuris vulpis) is substantially smaller than the other worms (a mere 30 to 50 mm in length, about a half inch maximum) and is rarely seen as it lives in the cecum (the part of the large intestine where the small and large intestine meet). The "head" (or more accurately the digestive end of the worm) is skinny vs. its stout tail (or reproductive end) which gives the worm a whip shape, hence the name.

In the digestive tract, food passes from mouth to esophagus to stomach to small intestine to large intestine to rectum and then to the outside world. This means the large intestine is one of the last stops for nutrients and by this point in the journey, nutrients have largely been broken down and absorbed. The large intestine (also called the "colon") serves to absorb water, to store fecal material, and to provide a home for a spectacular number of bacteria who are able to digest the leftover food that we cannot.

Whipworms developing in the soil. Note the characteristic plugs on either end of the egg.

Once in the outside world, the eggs require about 2 to 4 weeks to form embryos and become capable of infecting a new host. (This means that contaminated soil is the source of infection, not fresh feces.) The new host is infected from consuming the egg. The egg hatches in the small intestine releasing a larva. The larva dives into the glandular tissue of the small intestine and after about a week emerges into the small intestine and is carried into the large intestine with the intestinal contents.  Once in the cecum, its permanent home, it embeds in the tissue there, and after a total 74 to 87 days from the time the egg was swallowed, the young whipworm is ready to mate.

A few whipworms generally do not pose a problem for the host but if large numbers of worms are present embedding themselves in the large intestine tissue, tremendous inflammation can result leading to a bloody, gooey diarrhea. Usually there is not enough blood loss to be dangerous but the diarrhea readily becomes chronic and hard to control. 

A second syndrome of infection has emerged but is not well understood, this being symptoms mimicking those of Addison's disease (hypoadrenocorticism).  Here, a waxing and waning weakness with inability to conserve salt ultimately creates a dehydration crisis.  The syndrome mimics Addison's disease in every way except that testing for Addison's disease will be negative and deworming yields a complete recovery.

Because female whipworms only periodically lay eggs (whereas other worm females lay eggs continuously), a fecal sample tested may easily be negative for eggs. This makes the confirmation of a whipworm infection a challenge. It is common to deworm for whipworms if the symptoms are suggestive of the whipworm presence even if the fecal test is negative. 

More recently, regular heartworm prevention products have been developed to remove and control whipworms: Sentinel and Interceptor both will cover whipworms and their regular use covers the second deworming as well. Heartgard products do not carry a high enough dose of ivermectin to kill whipworms, though at other doses ivermectin could be used (with appropriate cautions). 

Soil contaminated by whipworm eggs is contaminated for years. It is virtually impossible to remove the eggs from the soil or kill them. Happily, however, this is one pet intestinal parasite that is not readily transmissible to humans.

Cats do not get infected with Trichuris vulpis, they have their own whipworm species: Trichuris campanula. This infection is very rare in the U.S. and is not felt to be of clinical significance. If whipworm eggs are seen in a feline fecal sample, the infection can be cleared with Panacur as noted above for dogs.

Date Published: 5/8/2004
Date Revised: 02/27/2006