Some very common symptoms can help you diagnose cat worms.
Depending on the type of worm, your cat may exhibit symptoms like chronic diarrhea and sometimes something as simple as lethargy.
Roundworms
Two types of roundworms, the Toxocara cati and Toxascaris leonine are the most common parasites that may affect your cat. These are normally 2 to 4 inches long, milky white or tan in color with tapering ends. The common symptoms when your cat is suffering from roundworm infection would be vomiting or chronic diarrhea and weakness and inactivity in adult cats while the kittens would have a pot belly. You cat will throw the roundworms out of her body through vomit or stools. The excreted worms will resemble spaghetti.
If you find that your cat has been infected by roundworms you may want to seek immediate medical help as these roundworms can spread to humans too.
Hookworms
Hookworm type Ancylostoma braziliense is also common in felines. However these are invisible to the naked eye. Hookworms feed on your cat's blood and can cause anemia. They can also be fatal if not diagnosed and treated, especially in kittens. Adult cats build up immunity and may not show any symptoms of infection. Kittens infected by hookworms will have severe abdominal pain, diarrhea and blood in their stool. Hookworms can also be transmitted to humans and should be treated immediately once diagnosed.
Tapeworms
Tapeworms type Dipylidium caninum and T. taeniaeformis infect cats, especially those infested by fleas. Tapeworms like roundworms are visible to the naked eye. Being small and white in color they can be found in the stool of your cat if infected. They can also be found in your cat's fur and around her tail. If you have a doubt that your cat is infected, observe her bedding closely. Dead segments of tapeworms will be visible as tiny balls that look like rice grains.
Another symptom is your cat will be constantly hungry and eat well, yet lose weight. The tapeworms are ingested by your cat along with the fleas which are the carriers of the parasite. Once inside your cat's stomach the parasites will line the intestinal wall and reproduce quickly causing pain, discomfort and loose stools. Tapeworms fortunately do not spread to humans.
Stomach Worms
Worms like Ollanulus tricuspis and Physaloptera breed in the stomach of your cat.
Ollanulus tricuspis, though rare in the U.S., can be found in stray cats, household cats and facilities housing multiple cats. These worms normally enter the cat's stomach when the cat eats the vomit of another infected animal. Common symptoms are weight loss, vomiting and lethargy. These worms can only be identified by your vet through tests of the infected vomit.
Physaloptera is normally present in cricket, cockroaches and rodents and enters the cat's stomach when she eats these. Symptoms are loss of appetite, vomiting and lethargy. Here too the vet will identify the worms through the presence of eggs in the vomit.