Roundworms are the most common of the parasitic worms found inside a cat (or dog). Almost all cats become infected with them at some time in their lives, usually as kittens. Roundworms may be contracted in different ways, making them easy to spread and hard to control.
Your cat may take in (ingest) infective roundworm eggs from the area where it lives or by eating mice or other small animals ("hosts") carrying young worms (larvae). Infection in kittens may also occur through the mother's milk.
Adult roundworms live in the cat's intestines. Most cats will not have signs of infection; however, cats with major roundworm infections commonly show vomiting, weight loss, dull hair, and a potbellied appearance. The cat may cough if the roundworms move into the lungs.
You may notice adult roundworms in your cat's feces or vomit. They will appear white or light brown in color and may be several inches long.
Because roundworms can enter your cat's body in many different ways, it is essential to keep your cat's living area clean (regular cleaning of the litter box) and, if possible, keep your cat indoors to prevent it from eating wild animals that may carry roundworms.
Kittens should be treated for roundworms every 2 weeks between three and nine weeks of age and then receive a preventive treatment monthly. Fecal (stool) examinations should be conducted 2 to 4 times during the first year of life and 1 or 2 times each year in adults. Nursing mothers (queens) should be kept on monthly preventive and treated along with their kittens. A monthly parasite control product effective against roundworms is recommended to treat potential new infections. Many heartworm medications also control roundworms so ask your veterinarian about prevention and treatment choices.
Roundworms do pose a significant risk to humans. Contact with contaminated soil or feces can result in human ingestion and infection. Roundworm eggs may accumulate in significant numbers in the soil where pets deposit feces. Children should not be allowed to play where animals have passed feces. Individuals who have direct contact with soil that may have been contaminated by cat or dog feces should wear gloves or wash their hands immediately.