Parasites and worms are common in animals including heartworm, hookworms, roundworms, and tapeworms. Heartworm lives in the heart of dogs and can be fatal if left untreated. Hookworms, roundworms, and tapeworms infect the intestinal tract of pets and can cause health issues if not properly treated. Preventative medications and regular vet checkups are important for detecting and treating parasite infections in animals.