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What types of worms can affect cats?
Roundworms resemble white pieces of string and can be up to 15 cm long. Affected cats usually have one of two types of roundworms, Toxocara and Toxascaris. Roundworms are rarely seen because they stay in the intestines and are only very rarely shed. If roundworms are passed in faeces or vomited up, it usually means that there are huge numbers of worms present in the intestines.
Tape worms are long flat worms made up of many small segments and grow to a length of 50 cm. Tapeworms constantly shed segments filled with eggs that can often be seen in faeces and then resemble small - and occasionally mobile - grains of rice.
Lung worms do not live in the intestines, but usually in bronchi (the airways in the lungs). Lungworms are not a common problem in cats in the UK.
How cats get worms?
Worm eggs or larvae are taken up either by licking, grooming or by ingesting small prey, so outdoor and hunting cats will always have more worms than indoor cats. Often eggs or larvae can survive on the ground for weeks or months, some can be transported by air and larvae can move actively, so even by wandering into a sunny spot in the garden your cat may pick up worms. Some worm eggs are quite sticky and can stick to the coat or even to clothes or human skin and then be transferred to the cat.
Tape worms and lung worms usually have a complicated life cycle and require an 'intermediate host' (another species of animal) that the worm lives in for part of its lifecycle. When a cat eats all or part of this intermediate host, the worm larvae then settle in the bowel system and mature. In the case of tape worms, such intermediate hosts can be fleas or small prey animals like rodents. Cats infested with fleas and hunting cats are at risk of acquiring tape worms. Intermediate hosts for lung worms are slugs and snails and whilst cats are unlikely to eat them, they can be infected when hunting e.g. birds that have eaten small slugs or snails.
Most of the worms live in cat's intestines, but there are always some that are hidden away in other organs or tissues and stay inactive for long periods. These inactive stages are not reached by any worming product, and as they can become active at any time during the animal's life, a cat can suddenly have worms even if there has been no chance of new infection e.g. in cats that only live indoors. Such inactive worm stages become particularly activated when a queen is pregnant. They then move into the mammary glands and kittens will become infected by feeding off their mother. This makes it important to treat young kittens frequently against worms. No matter how diligent breeders or previous carers have been - kittens will almost always have some roundworms!
What are the clinical signs of worms in cats?
Light infestations of worms usually cause no clinical signs at all, especially in grown-up cats - as a result the owner of an infected cat may feel sure that their pet does not have any worms.
Heavy worm infestations can cause severe clinical signs and may be dangerous for kittens. Kittens can present with a pot belly, slow growth, vomiting and diarrhoea, a rectal prolapse or even a fatal blockage of their bowel system.
Cats of any age with heavy worm burdens can show weight loss, poor coat quality, vomiting and diarrhoea, pneumonia and other respiratory problems, and occasionally problems in other organs.
Can humans get worms from pets?
Toxocara roundworms from dogs can infect humans but rarely cause severe disease. Whilst there is no clear evidence to show that the cat forms of roundworm cause disease in humans, they may still pose a potential problem. In humans the worms do not mature as they do in dogs and cats, and instead the larvae wander through various organs.
Liver problems, epileptic seizures and blindness are among the (rarely) reported clinical signs in humans affected by Toxocara infection. Children and people with a compromised immune system are most commonly affected. Children are more susceptible to infection given their propensity to play in and sometimes eat contaminated soil. Treatment may or may not be curative and problems such as blindness in children can be permanent.
Occasionally humans are diagnosed with a cat tapeworm. This usually happens to children who have swallowed a cat flea and, while it is certainly a hygiene issue, it can be readily treated.
We obviously recommend regular worming to ensure that your cat stays healthy, but another important reason for recommending frequent worming of pets is to protect your family and other people in the community from worm-related health problems.
What can be done to prevent problems?
The best way to prevent worm related health problems both in cats and human beings is regular worming of your cats and diligent removal of cat faeces from the environment. Modern worming products available at your veterinary surgery have been tested for efficacy and safety to the pet. We recommend that kittens are wormed at 2, 5, 8 and 12 weeks of age, and then monthly until they are 6 months old. The mother should be wormed at the same time as the kittens until they are weaned. Adult cats should be wormed at least every three months. Hunting cats or cats with close contact to small children or adults with inefficient immune systems can safely be wormed on a monthly basis. Tablets are most commonly used, but if giving a tablet is a problem in your cat, then effective spot-on products are also available. We will be happy to advise you on the most appropriate product for your cat.
If you have any queries or concerns, or if you would like to organise worming treatment for your cat, please do not hesitate to contact us.