Surveys consistently identify whipworms (Trichuris vulpis) as one of the most common parasitic worms of dogs in North America, while only infrequently being reported in cats or humans. They live in the lower aspects of the intestines (the cecum and colon) where they latch on to feed. Sometimes they cause no problems at all but they may cause abdominal upset (colic) or diarrhea, often tainted by blood and mucus. When eggs are laid in the intestines, they pass into the feces and become infective within 9-10 days. When consumed by dogs the infective eggs hatch in the intestines and the larvae parasitize the intestines and matures further.

      Many people do not realize that dogs do not begin to shed whipworm eggs in their stool until about 3 months after being infected. At that time each female whipworm may pass from 1000 to 4000 eggs per day into the stool. Complicating matters further are that female whipworms are long-lived, surviving for months or years in the intestines. The life cycle therefore includes a larval stage in the small intestine, an adult stage in the large intestine, and infective eggs that pass into the feces.

      Diagnosis is not always easy since it depends on finding whipworm eggs in the feces. Remember that animals are infected for 3 months before they begin to shed eggs and you can appreciate the problem. Once females begin shedding eggs, they are usually recoverable by direct smears and centrifugal flotation. They are not as easily found with standard fecal evaluations. In some instances, the adult worms are actually seen attached to the lower bowel during endoscopic procedures.

      Treatment is also not straightforward because of the peculiar life cycle of this parasite. Although many medicines are effective in removing adult worms, the larvae are less reliably cleared. Therefore treatment must often be repeated in 3 weeks and often, in 3 months as well, when the larvae have evolved into egg-producing adults. The biggest hindrance to effective treatment is that animals are often re-exposed to environments in which whipworm eggs are plentiful, and are thereby re-infected.

      It can be difficult to control exposure to whipworm eggs on lawns or soil but concrete can be effectively disinfected. Proper disposal of egg-containing dog feces is critical.

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Jun. 2, 2008 at 5:45 PM Ugh!  I don't even want to think about worms!  I just dewormed my dogs, because one of them had  a big ass roundworm in his poo yesterday.  Talk about gross.  It looked like a beansprout.

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