Although the source of a worm infection depends on the cat's environment and the type of parasite, cats often contract these worms from something they eat. Contact with feces or with soil can also transmit worms.
Tapeworms, lungworms, hookworms and roundworms are four of the parasites found in cats. If a cat eats a rodent infected with tapeworms, the tapeworms can easily transfer to the cat. It may be possible to see segments of a tapeworm in a cat's stool. Cats get lungworms by eating slugs, birds, rodents or snails infected with the parasite. This type of infection usually doesn't cause any symptoms, but experts from the ASPCA say an infected cat may develop a cough.
Hookworms live in the small intestine and get their nourishment from a cat's blood. Cats develop hookworm infections by coming into contact with hookworm larvae. The larvae are found in an infected cat's feces, so it is possible for another cat to ingest it. Roundworms are very common in cats. Adult cats get them when they come into contact with the feces of an infected cat or eat a rodent that has been infected. Kittens can also get roundworms through milk from their mothers.
Cats are more likely to develop parasitic infections if they don't get regular veterinary care or if they live outside and have a lot of contact with soil.