Whipworms are small, thin parasites that live within the lining of the colon (large intestine) and cecum. Whipworms infect dogs of all ages. Symptoms of whipworms cause diarrhea, blood or mucous in stool, and sometimes massive rectal bleeding. In severe cases the whipworms can cause the intestines to telescope on itself damaging the intestines which may result in a major surgery to remove that section of the intestines. Whipworms are diagnosed via microscopic examination of a stool sample. Medication is available for the treatment of whipworm infection. Sometimes pets need multiple treatments in order to eliminate the parasite, therefore multiple stool samples may be evaluated throughout treatment. Whipworms are extremely difficult to eliminate from the environment. Daily disposal of stools may be needed to prevent future infections and infestations. Monthly use of some heartworm preventions helps treat and control whipworm infections.