Roundworms, hookworms, and whipworms. These internal parasites cause symptoms such as vomiting, diarrhea, a pot belly and a dull coat. The symptoms become more serious and debilitating if your cat's condition is left untreated. Your veterinarian can diagnose these parasites by examining a fecal sample under a microscope. The various treatments may involve several doses before these parasites are eliminated.

Tapeworms. These internal parasites are picked up by ingesting rodents or raw meat or fish, or from adult fleas that are carriers. Tapeworms are passed through the cat's feces. Often you can spot tapeworm segments in your cat's stool or under her tail—they look like small grains of rice. If you see signs of tapeworms, bring a fecal sample to your veterinarian to get worming medication for your cat. You may need to start a flea control program at the same time. Never use over-the-counter worming products. These are usually ineffective and can cause unwanted side effects in your cat.

Coccidia. These internal parasites are picked up from the infected feces of other animals. Symptoms can be nonexistent or quite serious; they include mild to severe diarrhea, weakness, depression, loss of appetite and weight loss. Your veterinarian will need a fresh fecal sample to diagnose the problem and prescribe medication for these parasites.

Ringworm. Cat Ringworm is not a worm, but a fungal infection technically called dermatophytosis. It’s called ringworm due to its appearance - in humans, it appears as a crusty red circle with a pale center. That’s right, people can get ringworm, too. You can get it from your cat, or she can get it from you.  For more information about ringworm click here, or do an internet search and you'll find loads of information! 

Toxoplasma gondii. This small parasite may be of concern to humans as well as cats, especially people with compromised immune systems. Toxoplasmosis has traditionally been a reason for pregnant women to think they must give up their pet, but this is not necessary. Safe handling of food and water and precautions when cleaning the litter box can easily prevent the transmission of this parasite; that's why it's best to assign someone else the responsibility for cleaning the litter box. The majority of toxoplasmosis infections in humans have been the result of ingesting raw or undercooked meat. Cats become infested with this parasite through eating raw prey, but only pass contagious feces for approximately two weeks (and the feces themselves are only infective after 24 hours have passed). To prevent infection, keep your cat safely confined and feed him commercial cat food.