Whipworms are intestinal parasites which live in the cecum and colon (large intestine) of dogs where they cause severe irritation to the lining of those organs. This results in watery, bloody diarrhea, weight loss, and general debilitation. The eggs are periodically shed in the feces where other dogs can become infected by sniffing or licking the ground, and the eggs survive for long periods of time in the environment. Whipworm infection is more common in adult dogs, and can be very challenging to diagnose and to treat, due to the life cycle of the parasite. It is possible to detect the eggs on a fecal check, however, they may be difficult to find since they are only shed intermittently. Two treatments of a whipworm dewormer are needed at a 3-4 week interval, but because re-infection is such a problem, it is advisable to treat again every 3-4 months or to put the dog on a heartworm prevention product that contains an ingredient that prevents infection with whipworms.