The whipworm, Trichuris vulpis,is a parasite that invades the cecum and colon of dogs.
In milder infections, the worms are restricted to the cecum, but as the number of worms increases, they also invade the colon. In very serious cases, worms can cover most of the wall of the large bowel, from beginning to end (cecum to rectum).
There are often no symptoms of the presence of whipworms, but a heavy infestation can cause intermittent bloody diarrhea with mucus.
Some interesting Trichuris vulpis facts:
- Whipworm infections are seen in dogs, foxes and coyotes
- A female whipworm can produce more than 2000 eggs a day and whipworm eggs, which are thick walled and highly resistant to heat and drying, can live in the environment for years
- A dog with a whipworm infestation may show clinical signs before eggs are shed in feces; eggs can be shed sporadically
What Exactly Is a Whipworm?
Whipworms are parasites. The whipworm gets its name from its shape. Adult whipworms have a whip-like form -- the front end is narrower than the back end.
Full grown whipworms are no more than three inches in length. Males are quite a bit smaller than females.
The whipworm lives in the large intestine of dogs and can cause serious irritation to the lining of the colon. Adult worms dig their heads (at the thin end) deep into the intestinal mucosa and feed on material secreted by the tissues. There is often blood leakage as a result of whipworm tunneling and feeding activity.
Unlike other internal parasites, whipworms are very host-specific, meaning they rarely occur in species other than canines. They present no risk to humans. Feline whipworm infections are rare in North American domestic cats, and appear to be caused by a different species than Trichuris vulpis.
Whipworms occur in dogs worldwide, and are fairly common in shelter dogs in the U.S.
How Infection Occurs
Your dog can only get infected by ingesting whipworm eggs from soil or other substrates containing eggs.
In the small intestine, larvae hatch from ingested eggs and burrow into the mucosal lining. From two to ten days later, they move on to the dog's cecum and grow into adult worms. It takes from about 70 to 90 days from ingestion of whipworm eggs for new eggs to be shed in a dog's feces.
The eggs are not infectious when passed in feces. They need several weeks in soil to develop into infective larvae inside their shells. Dogs eat contaminated soil or objects in the soil and the cycle of infection begins.
Many dogs show no clinical signs of illness with a whipworm infection. Symptoms when they do occur can include:
- Bloody diarrhea
- Weight loss
- Death in severe cases
Most diagnoses are made when whipworm eggs are detected in feces. However, diagnosis can also be reasonably made in the absence of shed eggs by assessing the dog's history, clinical symptoms, and response to treatment.
There are six products with tongue-twisting names in a class of drugs called anthelmintics which are approved for use in the U.S. against whipworms. These include:
- Fenbendazole Q 24 H at 50 mg/kg for 3 days
- Febantel once at 25 mg/kg, formulated with 5 mg/kg praziquantel and 5 mg/kg pyrantel pamoate
- Milbemycin oxime monthly at 0.5 mg/kg, formulated alone
- Milbemycin oxime monthly at 0.5 mg/kg, formulated with 10 mg/kg lufenuron
- Milbemycin oxime monthly at 0.5 mg/kg, formulated with 30 mg/kg spinosad
- Moxidectin monthly at 2.5 mg/kg, formulated with 10 mg/kg imidacloprid
The first two products are often needed in three consecutive doses to effectively clear whipworms in different stages of growth inside your dog's colon.
The last four products are what I call combination treatments which claim to kill both heartworms and whipworms, along with other internal parasites. They are prescribed for monthly use. I don't agree 'more is better' when it comes to drugs for your pet. If your dog has whipworms, treat the whipworms specifically, and only long enough to clear the infection. If your dog is at risk of acquiring heartworm disease, tackle that issue separately.
Some integrative vets will offer natural dewormers for whipworms. I have tried them all and frustratingly, I have not found a protocol that effectively eliminates this parasite consistently. Sometimes they work, sometimes they don't. It's fine to try natural deworming first, but making sure these resilient parasites are truly eliminated is of utmost importance to avoid chronic, avoidable GI problems.
Unfortunately, re-infection with whipworm from contaminated environments is a significant concern. The eggs are extremely resilient and they are resistant to most cleaning methods and even freezing temperatures. They can be dried out with strong agents like agricultural lime, but the preferred method is to replace contaminated soil with new soil or another substrate.
Regularly picking up feces from your yard and other areas your dog inhabits will also help reduce the risk of further contamination of soil.
To keep your dog's GI tract in excellent shape and resistant to parasitic infections, make sure to feed a balanced, species-appropriate diet.