Whipworms (Trichuris) are a common intestinal parasite in dogs. In adults, they more often cause clinical signs than other types of parasites do. Many infections are asymptomatic, but heavy infections cause intermittent diarrhea containing mucous and blood. These cases can be very debilitating to an adult dog, not to mention a puppy. The parasites body (difficult to see with the unaided eye) is whip-shaped with one end being stout and the other end fine and hair-like. This adult worm lives in the dogs large intestine and cecum. The egg is passed in the stool and is very resistant. Thus, a contaminated environment will cause a dog to become reinfected after treatment. Pyrantel pamoate (Strongid T, Anthelban) will not eliminate this parasite, so Panacur must be used. Treatment of puppies less than 12 weeks of age is minimally effective, so it is very important to treat the adult female to reduce puppy exposure.