One of the most definite ways to identify worms in dogs is finding visible worms in the dog's stool or vomit. Other signs to identify worms in dogs include diarrhea that may contain blood, weight loss, dry hair and an overall poor appearance.
The most common worms that infect dogs are roundworms, hookworms, whipworms and tapeworms. The only two types of worms that are frequently seen with the naked eye in the stool of dogs are roundworms and tapeworms. Hookworms and whipworms can only be detected microscopically, when their eggs are viewed in stool samples. Whipworm infestations are typically difficult to detect because the worms shed comparatively fewer eggs than other parasitic worms. This means that examining the stool of infected dogs may not reveal the presence of the worms.
Puppies that are infested with active roundworms in their intestines often have a pot-bellied appearance and poor growth. Dogs that are infected with whipworms typically have chronic weight loss. The dogs may also pass stool that appears to have a covering of mucus, especially around the last portion that is passed. Dogs that have a severe hookworm infestation may be severely anemic due to blood loss caused by the feeding activities of the worms. Some signs include poor stamina and feed efficiency, weight loss and progressive weakness.