What are whipworms?
Whipworms are intestinal parasites that are about 1/4 inch (6 mm) long. They live in a dog’s large intestine and cecum (a pouch that forms the first part of the large intestine), where they cause severe irritation to the intestinal lining. Of all the intestinal parasites found in dogs, whipworms cause the most disease. The most common whipworm species affecting dogs is Trichuris vulpis, which is also found in foxes, coyotes, and other canines.
How do dogs get whipworms?
Whipworms pass microscopic eggs in the stool. The eggs are resistant to drying and heat, and they can remain alive in the environment for up to five years. Once laid, the eggs mature to an infective stage (a process known as embryonation) in the environment and can infect another dog in 10 to 60 days. The mature eggs are swallowed by the dog, then hatch and mature into adults in the lower intestinal tract, completing their life cycle.
What are the signs of whipworms?
Whipworm infection can cause bloody diarrhea, weight loss, changes in electrolyte concentrations, and general debilitation. Smaller infestations may be asymptomatic.
How are whipworms diagnosed?
Whipworms are diagnosed by finding eggs on microscopic examination of the stool. These eggs, however, are difficult to find. Whipworms pass small numbers of eggs on an inconsistent basis, so some samples may be falsely negative. Multiple stool samples are often required to diagnose whipworm infection.
Additionally, it takes approximately 11 to 12 weeks after hatching before a female adult begins to lay eggs, so tests run soon after infection are often falsely negative. Newer testing looks for whipworm DNA in the feces, and while it is more effective, there are still false negatives.
Any dog with chronic diarrhea should be suspected of having whipworms, even if the stool sample is negative. Thus, it is an accepted practice to treat chronic diarrhea by administering a broad-spectrum dewormer. Response to treatment indicates that worms were present but could not be detected on fecal examination.
How are whipworms treated?
Several medications are effective against whipworms. Medications used for whipworms include fenbendazole (Panacur®, Safeguard®), milbemycin oxime (Interceptor®), and moxidectin + imidacloprid (Advantage Multi®). All medications must be repeated monthly for three months to clear the infection.
The most frustrating part of whipworm infection is the high re-infection rate, since whipworm eggs are extremely hardy in the environment. For that reason, if a dog is diagnosed with a whipworm infection, it is advisable to treat it again every three to four months.
A simpler option is to use a heartworm and flea preventative that is effective against whipworms. Whipworms are far less common today than in the past, because of the widespread use of modern heartworm prevention products. Your veterinarian will advise you on the best treatment option for your dog.
Can I get whipworms from my dog?
Whipworms are species-specific parasites and do not infest humans as they do cats and dogs. Transmission to humans is unlikely, although there have been rare cases of abnormal whipworm infection in people. The best prevention is prompt, hygienic removal of pet feces and regular deworming of all pets.
