Intestinal worms are a common problem in cats. While they are unlikely to cause life-threatening disease in healthy adults, they can cause serious disease in kittens and in cats that are ill for another reason. It is also possible for certain worms or other intestinal parasites from cats to infect humans. This means it is very important to be careful about litter tray hygiene and to give preventative worming treatment to your cat on a routine basis. There are many treatments available that can effectively prevent and treat worms in cats.

What happens when a cat is infected with worms?

Worm infection does not always cause symptoms in cats. When symptoms do develop, these arise because worms deprive your cat of nutrients and can also irritate the intestines and damage the delicate gut lining. Signs of intestinal worm infection include weight loss, poor condition, a pot-bellied appearance, diarrhea and anemia.

Worm infection can be very serious in kittens and it can even be fatal if the worm burden is high enough. In some cases, there can be so many worms present that the intestines can become blocked.

There are several types of intestinal worms that can affect cats, as well as other single-celled intestinal parasites as well. Different parasites can cause slightly different symptoms.

What types of intestinal worms can infect cats?

The most important types of worms for cats are roundworms and tapeworms, though other types including hookworms and whipworms can also cause infection. Alongside these worms, other important intestinal parasites are Toxoplasma and Giardia.

Roundworms

Roundworms look a bit like white spaghetti. They live in the cat's intestines where they can grow to about 15 cm long, and they lay a lot of eggs which are passed out in the cat's faeces. These eggs can then be either eaten directly by a cat, or be eaten by another animal such as a rodent. If the latter happens, the roundworm larvae then live in little 'cysts' in the tissues of the rodent. A cat can then be infected again by eating the rodent.

In the cat's body, some worm larvae may pass into other tissues such as the liver or muscle, Larvae can also cross the placenta and infect kittens, or be passed on in the milk when kittens are suckling. This is one of the reasons why it is so important to follow a thorough worming regime for pregnant cats and young kittens.

Animation on the roundworm life cycle:

With roundworms, it is important to remember that the larvae can occasionally infect humans. Although this is very rare it can be serious, as the larvae can migrate into the eye and cause blindness in children. Because of this, it is important to keep your cat dewormed and to make sure that your children wash their hands after they have been playing in areas where cats may have toileted.

Tapeworms

Tapeworms attach to the lining of the intestine and grow by forming new segments (proglottids) containing eggs. These segments fall off and are expelled with feces. They look like grains of rice. The proglottids break and the eggs are dispersed in the environment. Flea larvae can ingest them and become contaminated. The tapeworm eggs will locate and develop in the flea larva. When the flea becomes an adult it will contain a mature form (cysticercus) that can infest the cat. When the cat swallows a flea, it will infest itself and develop adult tapeworms.

Animation on the tapeworm life cycle:

Toxoplasma

Toxoplasma gondii is a tiny parasite that lives in the cat’s intestines. The parasite sheds little ‘oocysts' that are passed in the cat's feces. These become infectious after 1-5 days in the environment, and they can be picked up by an 'intermediate host' such as a rodent or bird. The immature parasite then forms cysts in the tissue of the intermediate host, and infects a cat again when they catch and eat the host.

Animation on the life cycle for Toxoplasma:

Toxoplasma rarely causes disease in cats, but it is important to be aware of because it can also infect humans. While Toxoplasma infection does not often cause problems in humans, it is a bigger risk for people with compromised immune systems, and pregnant women are also at risk as it can potentially spread to the unborn fetus and cause problems. This means that pregnant women are advised not to clean out cat litter trays if someone else is able to do it. If there is no other choice, it is important to wear gloves and wash hands thoroughly afterwards. Litter trays should be cleaned daily if possible, as the parasite only becomes infectious after a day in the environment. People can also pick up Toxoplasma from eating undercooked contaminated meat, so it is important to take basic hygiene measures and cook meat thoroughly.

Giardia

Another intestinal parasite of cats is Giardia. This is a small parasite that can cause diarrhea in cats, and can also potentially spread to humans who can develop similar signs. To avoid this, it is important to take basic hygiene measures and be careful when picking up cat feces and cleaning litter trays. Giardia’s life cycle is simple: the parasite is passed out in feces, and when another host eats something contaminated with the feces, they will pick up the parasite.

Animation on the life cycle for Giardia:

When should I treat my cat for worms?

It is not always obvious when your cat has worms. While some cats will be ill and show the symptoms described above, others may appear perfectly well. In some cases, you may see roundworms or tapeworm segments in your cat's feces, or you might notice tapeworm segments migrating in the fur around their back end. However, other times you may see no signs at all. If your cat goes outdoors, it is best to assume that they will come into contact with worms from the environment or from fleas, and treat them on a routine basis.

Many different cat worming treatments are available. Some only protect against certain types of worms, so your vet will be able to advise on which treatment is best for your pet. Kittens should be wormed more frequently: the general advice is to treat every two weeks till 12 weeks of age, then every month till 6 months, then every three months after that. However, cats who are active hunters may require more frequent worming than every three months, as worming treatments do not have residual effects so cats can become reinfected quickly after dosing. It is also important to check your pet regularly for fleas and treat as necessary, as this will break the lifecycle for the most common cat tapeworm.

Animation on worm contamination for cats:

It is always sensible to take other basic hygiene measures to reduce the likelihood of worm infection, such as cleaning up cat feces promptly and making sure your children wash their hands after playing anywhere where a cat may have toileted. Because of the risk of Toxoplasma, pregnant women are advised to avoid cleaning out litter trays if possible, and to use gloves and strict hygiene if they need to do so. Litter trays should be cleaned out daily as the parasite only becomes infectious after a day in the environment.

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