Roundworms (Ascarids) are a common intestinal parasitic worm. There are two species which affect cats, Toxocara cati and Toxascaris leonina. Toxocara cati is more commonly found in cats. Roundworms feed upon the intestinal contents, competing with the host for food.
Roundworms are around 3 - 5 inches long and spaghetti like in appearance.
There are three modes of transmission, all of which occur when the cat consumes the infective eggs. It is possible for larvae to be encysted in the tissues from an earlier infection.
- Transmammary transmission (Toxocara cati): When a cat is infected with roundworm, some larvae migrate to other tissues in the body. Pregnancy re-activates these larvae which migrate to the mammary glands and are passed onto the kittens via the mother's milk.
- Hunting: Rodents can act as intermediate hosts to roundworm and when a cat kills and consumes its prey.
- Environmental: Cats ingest roundworm eggs containing infective larvae from the environment such as soil, or when they come into contact with the feces of an infected cat.
Life cycle of roundworms
Eggs are passed in the feces, at this stage, they are not infective. Once in the environment, they develop into what's known as "second stage larvae". This takes around three weeks. It is at this time that they become infective. Eggs can survive in the environment for months.
The cat ingests the egg containing the infective larvae. Once inside the cat, they hatch in the cat's intestinal tract. The larvae migrate to the liver and other organs. In the liver, they develop into the third stage. They then enter the bloodstream and migrate to the lungs. Once in the lungs where they develop into the fourth stage larvae. They are coughed up and into the throat and then swallowed, re-entering the intestinal tract for a second time. Once in the intestinal tract they mature and begin to mate. The female lays her eggs which are passed in the feces and so the cycle begins once again.
Some of these become encysted in the tissues where they are inactive (or dormant). When a cat is wormed, the worms in the intestines are killed but the encysted larvae.
In rodents, the animal swallows the roundworm eggs which hatch inside the rodent's intestinal tract and then migrate to the organs where they become encysted. They are not able to complete their life cycle in rodents, but if cats eat infected prey, they can become infected.
As with Toxocara cati, the eggs of Toxascaris leonia are passed in the feces where they develop into the second stage and become infective. The larvae are consumed by the cat they hatch in the cat's intestinal tract.
There is no trans mammary transmission with Toxoscaris leonia.
- Poor coat condition, appearing rough and dull.
- Vomiting, if the infestation is heavy there may be worms present in the vomit.
- Pot-bellied appearance, especially in kittens.
- Severe cases can lead to pneumonia and intestinal and bowel blockage.
Diagnosis is performed by examination of the feces for the presence of roundworm eggs.
If the infestation is severe roundworms can lead to pneumonia and intestinal blockage. Also, as the roundworms are competing with the cat for food, it can result in your cat not receiving enough nutrients and becoming malnourished. This is usually seen in kittens.
There are many effective medications to treat roundworms. The most common types of worming medication are in tablet or topical form.
Some applications such as Revolution typically treat fleas and some varieties of worms such as roundworm, hookworm, and tapeworm and are administered onto the skin on the back of the neck once a month. See here for our quick guide to worming products.
Yes, even indoor cats can still potentially catch worms and should be regularly wormed unless advised otherwise by your veterinarian.
Yes and no. Mother cats can pass roundworms onto her kittens either via the placenta or her milk. Other than that, cats can't directly spread roundworm. Infection occurs via ingestion of the eggs from the environment. This is why it is extremely important to dispose of feces at least once a day.
Toxocariasis is a disease in humans caused by infection of the roundworm egg. Most cases have been identified as those of T. canis. Occasionally T. cati has been identified. In humans, roundworms can't go past "stage 2" (larval stage). As with infection in rodents, the larvae migrate to various tissues in the body (causing a disease called visceral larva migrans or toxocariasis) including the lungs, brain, eyes and liver.
There are two forms of toxocariasis:
- Ocular larva migrans (OLM) results from the larvae entering the eye, causing an inflammatory response, which leads to damage to the eye, in severe cases, it can result in blindness.
- Visceral larva migrans (VLM): The larvae migrate to the various organs and cause an (inflammatory immune response) which leads to damage to the organs.
The larvae can remain alive for many months, causing damage by migrating through tissues.
Humans are more commonly affected by pinworms, which are a common type of worm found predominantly in school-aged children.
- Preventing hunting behavior.
- If you are planning to mate your queen, she should be de-wormed prior to mating and receive another dose late in pregnancy.
- Kittens should be dewormed from two weeks of age, and every two weeks until they are 12 weeks old.
- Adults should be de-wormed every 3-6 months, or as stated on your worming medication.
- Keep litter trays clean, solids should be scooped at least once or twice a day and thoroughly disinfected once a week.
- Dispose of cat feces in the garbage, don't put it in the garden.