There are two species of roundworms that infect cats; both are round, up to four inches long, and white to pale brown in color (they look similar to spaghetti noodles). While one type of roundworm (Toxascara leonina) is dangerous only to cats, the other type (Toxocara cati) can cause health problems in humans, too.
What Are Roundworms?
Symptoms of Roundworms in Cats
The eggs of roundworms are detected under the microscope in a routine check of a stool sample (the test process is called fecal flotation). It is possible to tell the difference between the species of roundworm based on the appearance of their eggs. Of course, when roundworms appear in vomit or stool, the diagnosis is simple and immediate. The medical term for infection with roundworms is ascariasis.
Roundworms (both kinds) can produce any of the following symptoms, although symptoms may only appear with heavy infections:
- Failure to gain weight or weight loss
- Dull hair coat
- Pot-bellied appearance
- Kittens will sometimes vomit up roundworms or pass them in their feces
- Coughing due to the larval migration through the lungs
Rarely, very heavy infections can lead to blockage of the intestines, which will make a kitten very ill with vomiting and lethargy the major symptoms.
Types of Roundworms
There are two types of roundworms; while they look and behave similarly, they have different life cycles.
- Toxocara cati is seen commonly, especially in kittens as kittens can ingest larvae through their mother's milk. Both cats and kittens can also ingest eggs as a result of eating rodents or other carriers such as beetles or earthworms which are infected with Toxocara cati. The eggs then hatch into larvae inside the cat's digestive system.
- Toxascara leonina is far less common, and is more often seen in older cats (and dogs). It is rare for Toxascara leonina to infect human beings.
Toxascara leonina has a much more straightforward life cycle than Toxocara cati. The eggs are shed in the feces, and once ingested they develop into adult roundworms in the intestines (no migration required) that eventually shed more eggs. The eggs are only infective after several days to weeks in the environment. Rodents can also become infected with Toxascara leonina larvae, and cats can become infected from eating an infected rodent.
Causes of Roundworms in Cats
Cats ingest roundworm larvae in several ways: through mother's milk, by eating the eggs, or by eating another organism such as a beetle or rodent which carries roundworm larvae. The roundworm larvae (including those that are swallowed and ingested as eggs, which then hatch) migrate through the body tissues, with most eventually reaching the lungs, where they make their way up the windpipe and are coughed up and then swallowed.
Once swallowed this time, the larvae then become adult roundworms in the intestines. These produce numerous eggs, which are passed in the feces. Eggs only become infective after weeks in the environment. The eggs are hardy and can remain infective for months or years.
Sometimes the larvae stop their migration in the liver, where they enter a dormant state. In a pregnant female, these larvae become active again, and the larvae can be secreted in the milk after birth. They can also produce an active adult roundworm infection in the mom's intestines, so she then sheds numerous eggs that can also infect the kittens. Toxacara cati roundworms, in particular, have a life cycle that makes them very effective at infecting kittens.
Treatment is the same, regardless of the roundworm involved. There are a number of medications that can be used to treat roundworms, and your vet can help you pick the one right for your cat. Medications will only affect adult roundworms, however, so they need to be repeated at two-week intervals to deal with any residual larvae as they mature. The number of treatments necessary will depend on the age of the cat and the situation, which will be assessed by your vet.
If you have a pregnant cat, consult your vet for advice on deworming the mom and kittens. Once dewormed, many of the monthly medications designed for heartworm and parasite control contain medication that will prevent roundworm infections on an ongoing basis—options that can be discussed with your vet.
If your cat is not on one of these preventatives, your vet will recommend a regular deworming protocol to keep roundworms at bay. Cleaning up pet wastes promptly, and preventing pets from eating rodents can also help prevent infection with worms.
How to Prevent Roundworms
Roundworm generally infects cats who spend time outdoors or who spend time with outdoor cats, but it can pass from cat to cat through feces. While it's not impossible to contract roundworm from an insect or rodent that makes its way inside, such an occurrence is relatively rare. Keeping cats inside, therefore, is a powerful protectant.
Once roundworm is diagnosed, it's important to follow the vet's instructions carefully. In addition:
- Quarantine any infected cats or kittens until the infection is fully resolved
- Be sure to clean litter boxes as often as possible
- Clean all surfaces regularly throughout your cat's treatments
- Be careful to keep cat feces away from other animals and from children
- Practice good hygiene
Kittens should be checked for roundworm several times a year, while adults should be checked once or twice a year. The best way for your vet to diagnose roundworms is by examining a stool sample.
How Cat Roundworms Can Infect Human Beings
The larvae of Toxocara cati roundworms can infect people, as well as cats. This happens when eggs are ingested. It is most common in children who may not practice the best hygiene and may pick up eggs on their hands when playing in the yard, for example. Good hygiene is important; children should wash their hands regularly, and cats should be kept out of areas where children play. Sandboxes, not surprisingly, pose a particular challenge. It's also important to keep pet waste picked up.
The larvae don't develop into adult roundworms in people, but the larvae migrating through the tissues can cause inflammation, especially in young children. Most cases are not serious, but in serious cases, organ damage is possible, as result of the migrating larvae (such as the liver, lung, brain), and sometimes the larvae can reach the eyes, leading to visual disturbances and even blindness.
Migration of roundworm larvae through human tissues is called "visceral larva migrans," while migration to the eyes is called "ocular larva migrans." Proper prevention of a roundworm infection is important to prevent these human health problems.