Worm control

All pets will be affected by worms at some stage in their life and many will be re-infected unless they are given regular, routine worming treatment. Cats are natural hosts to a range of parasitic worms. Getting rid of worms is relatively simple and inexpensive so regular treatment is strongly recommended, particularly as some types of worm can be passed onto humans.

There are two important types of parasitic worms in cats – roundworms and tapeworms.

Roundworms can grow up to 15 cm long and are white in color. As their name suggests they are round (like string). Roundworm larvae (found in and near dog or cat feces) can pose a significant risk to human health, especially to children. Tapeworms are flat (like ribbons) and can grow up to 60 cm long. Both roundworms and tapeworms live in the cat’s intestines along with two other types of smaller worm (similar to roundworms) called whipworms and hookworms. These are parasitic worms that can live in the cat’s lungs, heart, stomach or bladder.

There are a range of treatments designed to kill worms. Some are highly effective, however, not all the products are equally good and some only work against certain types of worms and not others. There are a variety of active ingredients which work against different combinations of worms, and they come in various formulations such as liquids, pastes, pills and spot-ons. They also are all designed to be used at different intervals. It is best to consult your veterinarian as to which product would best suit your cat.

Homeopathic and herbal remedies are rarely effective. Non-prescription supermarket and pet shop brands are usually only effective against a narrow range of worm species. Veterinary and prescription wormers often use a combination of ingredients to target different types of worm simultaneously.

Worms are so common that it is safe to assume that all kittens, and animals which regularly catch wildlife will be infected. Fleas carry tapeworm larvae, so any cat with fleas should be assumed to have worms as well. Kittens should be treated with wormers every two weeks, from 6 weeks to 16 weeks of age, and older cats should be treated about every three to six months, dependent on individual risk. You should discuss with your veterinarian the most appropriate treatment regime for your pet.

Immature worms can be passed from a mother to her kittens, whilst they are still in the womb or via the milk. Roundworms grow in the intestine of young cats, laying thousands of eggs which pass out in the feces. Most adult cats develop a degree of immunity and do not pass eggs but some continue to do so throughout their life. The eggs can survive for months or even years in the soil and need to lie in the environment for some time before they can infect another animal. They find their way into a new host either directly (when eaten by a cat) or indirectly (after being swallowed by a rodent which is then eaten by the cat). Immature worms also survive in the tissues of an infected cat and can develop again if a female cat becomes pregnant.

Treatments for roundworms usually kill all adult worms in the intestine at time of treatment but do not have any long-lasting effect. This means that cats can easily be re-infected. It is not easy to tell if an animal has been re-infected and so treatment is usually just given at regular intervals to remove any worms present. It is likely that young cats will have roundworms and so treatment should be started at 6 weeks of age and continued at the recommended interval for the product used (usually every 2-4 weeks) until adulthood. All pregnant cats should also be treated for worms with a product suitable for pregnant queens to try and reduce worms being passed on to the more vulnerable pups.

Tapeworms are anchored by their head to the intestine wall and grow a continuous ribbon of segments, each packed with eggs. The segments gradually break off and are passed out in the feces. These segments look like grains of rice and may wriggle like a maggot for a short time before they dry up (sometimes still attached to your cat’s fur). The most common type of tapeworm moves on to a new cat by way of fleas. Immature fleas pick up infection from cat feces in the environment and cats are then infected if they accidentally swallow an adult flea during grooming.

There is also a less common type of tapeworm which uses mice, other rodents and rabbits to complete its life-cycle. This parasite lies dormant in the muscle or other organs of a small rodent or rabbit and cats are infected if they eat these animals.

This depends to some extent on your individual circumstances. Some indoor cats may never be exposed to worms and so do not need repeated treatments once worms have been eliminated as a kitten. Bear in mind that fleas can carry tapeworm, so even indoor cats who can’t hunt can be infected with worms if fleas are brought into the home.

The products usually used to treat worms do not have any persistent action so pets may become re-infected immediately after treatment. Most veterinarians recommend treating pets every 3-6 months but cats that do a lot of hunting or scavenging may need to be treated more frequently. You should ask your own veterinarian for advice on the best way to control infection in your pet.

There is a kind of roundworm (Angiostrongylus) that can live in the blood vessels of affected pets. Severe infection with this worm can cause lung disease and heart failure but also can result in problems with blood clotting. Other worms that live in the lungs or respiratory system (Aelurostrongylus in cats and Filaroides in dogs) can also cause coughing. Special tests are needed to identify infection with these parasites but they can be treated.

Hookworms and whipworms are rarely seen in pet dogs and cats in this country but may occasionally be seen where large numbers of cats are kenneled together. Infections with large numbers of worms may result in diarrhea and weight loss. Many of the routine drugs used for removing other worms are also effective against these.

Apart from regularly worming your pets, there are a number of other measures which can stop worms being passed on from cat to cat, or from cat to people.

• If your cat uses your garden as a toilet, clean up the feces and bury them or put them inside a sealed bag in your trash.
• Check your cat for signs of fleas and treat them regularly using the product recommended by your veterinarian. Fleas are more numerous during summer and fall, although will survive all year round in centrally heated homes.
• Children will put dirty fingers and other objects into their mouths, and this may bring them into contact with worm eggs. Make sure that they wash their hands after playing in any open areas which may have been used as a toilet by cats. Remember the greatest risk of children being infected with worms is from other children, not your cat.