Whipworms in the Dog

Filed Under: Dogs, Parasites

Does your dog have bloody diarrhea? Make sure your veterinarian does multiple fecal samples to check for whipworms or Trichuris vulpis. The eggs of Trichuris are not as buoyant as the eggs of many other parasite species, often necessitating special procedures to confirm a diagnosis. These thread-like inhabitants of the cecum have a bad habit of causing anemia, dehydration, and even death in addition to bloody diarrhea. A recent study determined that 14.3% of the canine population may be infected.

The worm is actually whip-shaped, hence the name. The worm embeds itself into the walls of the large intestine and cecum (a sac-like structure between the large and small intestines). Female whipworms do not produce eggs every day but rather intermittently. Compared to many species of parasites, the female whipworm parasite produces only between 4,000 and 8,000 eggs per day when productive. The eggs are passed out in the stool where they become infective first-stage larvae in as little as 9 to 10 days at 36°C, or in as long as 25 days at an ambient temperature of 25°C.

Whipworms have what is termed a "direct lifecycle", involving only one susceptible host -- a canine. The eggs are passed in the stool where an infective first-stage larva will develop within the egg but will not hatch unless swallowed by an appropriate host. Once the larvated egg is ingested, the larva will be released into the small intestine where they then colonize the cecum and large intestine around 15 days after introduction. After 3 months of development the female worms will begin their intermittent shedding of eggs.

The prepatent period, or the time between infection with Trichuris until the time when adult whipworms are producing eggs, takes between 70 and 100 days.

The concept of intermittent shedding of eggs by the whipworm is important because multiple fecal analyses may be necessary to diagnose the infection. Clinical signs of infection may also be apparent before the appearance of eggs in the stool. Diagnosis of a whipworm infection may therefore be difficult and may be made on clinical signs alone before confirmation is possible. Centrifugation of a stool sample is the most accurate type of fecal analysis currently available for whipworm diagnosis.

In a survey of shelter dogs, adult dogs were almost as susceptible to infection to Trichuris as were younger dogs. Foxes and coyotes are both hosts for this parasite and will act as a reservoir for infection for domestic dogs.

Eggs may persist in the environment for up to 7 years, thereby making control difficult. The eggs survive best in damp, shady areas of soil.

Treatments for whipworms include the following: Febantel is an anthelmintic that may be found alone or in a combination drug by the name of Drontal Plus®, developed by Bayer Animal Health. Fenbendazole is also an anthelmintic found alone in a product known as Safe-Guard® canine dewormer. Safe-Guard is available from Intervet/Schering-Plough Animal Health. Milbemycin is an anthelmintic and a heartworm preventative available from Novartis Animal Health by the name of Interceptor® or Sentinel®. An additional anthelmintic/heartworm preventative containing moxidectin and Imidacloprid is available under the name of Advantage Multi®, available from Bayer Animal Health. When an anthelmintic is a heartworm preventative or used in combination with a heartworm preventative, the dog should be tested for heartworms and determined to test negative or be on a current, adequate heartworm preventative schedule before beginning treatment. The administration of a heartworm preventative in a heartworm positive canine may cause the development of a severe or even deadly allergic or anaphylactic reaction to occur. One treatment may be up to 90% effective, however due to the risk of reinfection, more than one treatment may be necessary. Most treatment protocols involve multiple deworming at intervals of 3 to 4 weeks in duration.

References:

Blagburn, Byron. “The Elusive Whipworm, Trichuris vulpis.” Clinician’s Brief. September 2008. P. 2-4.

Bowman, Dwight. “A Clinical Overview of Whipworms.” Veterinary Forum. August 2008. Pp. 48-50, 70.

Topics: whipworms, worms

Symptoms: diarrhea

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