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. Dogs 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.
What sort of worms affect dogs?
There are two important types of parasitic worms in dogs: roundworms and tapeworms.
Roundworms can grow up to 15 cm long and are white in colour. As their name suggests they are round (like string). Roundworm larvae (found in and near dog or cat faeces) 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 dog's intestines along with two other types of smaller worm (similar to roundworms) called whipworms and hookworms.
There are also parasitic worms that can live in the dog's lungs, heart, stomach or bladder. Lungworm is a type of roundworm whose eggs hatch in the lungs of dogs, and can be fatal. It is becoming much more common in the UK in recent years.
How can worms be destroyed?
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, tablets and spot-ons. They also are all designed to be used at different intervals. It is best to consult your vet as to which product would best suit your dog.
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 puppies, and animals which regularly catch wildlife will be infected. Fleas carry tapeworm larvae, so any dog with fleas should be assumed to have worms as well. Puppies should be treated with wormers every two weeks, from 6-16 weeks of age. Your vet will advise on a suitable interval between treatments thereafter, depending on risk. Older dogs should be treated about every three months. You should discuss with your vet the most appropriate treatment regime for your pet.
How can I treat roundworms in my pet?
Immature worms can be passed from a mother to her puppies, whilst they are still in the womb or via the milk. Roundworms grow in the intestine of young dogs, laying thousands of eggs which pass out in the faeces. Most adult dogs 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 dog) or indirectly, (after being swallowed by a rodent which is then eaten by the dog). Immature worms also survive in the tissues of an infected dog and can develop again if a female dog becomes pregnant.
Treatments for roundworms usually kill all adult worms present at time of treatment in the intestine but do not have any long-lasting effect. This means that dogs can easily be reinfected. It is not easy to tell if an animal has been reinfected and so treatment is usually just given at regular intervals to remove any worms present. It is likely that young dogs 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 dogs should also be treated for worms with a product suitable for pregnant bitches, to try and reduce worms being passed on to the more vulnerable pups.
How can I treat tapeworms in my pet?
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 faeces. 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 dog's fur). The most common type of tapeworm moves on to a new dog by way of fleas. Immature fleas pick up infection from dog faeces in the environment and dogs 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 dogs are infected if they eat these animals.
How often do I need to treat my pet?
This depends to some extent on your individual circumstances. The products usually used to treat worms do not have any persistent action so pets may become reinfected immediately after treatment. Most vets recommend treating pets every 3-6 months but dogs that do a lot of hunting or eat faeces or dead wildlife out on walks may need to be treated more frequently. You should ask your own vet for advice on the best way to control infection in your pet.
Are there any other worms I should worry about?
There is a kind of roundworm (Angiostrongylus) commonly called lungworm, that can live in the blood vessels of affected pets. This should now be considered to be present throughout the UK and cases have rapidly increased over the last few years. 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 dogs are kennelled together. Infections with large numbers of worms may result in diarrhoea and weight loss. Many of the routine drugs used for removing other worms are also effective against these.
If you travel abroad with your pet they may need to be treated to remove all tapeworms 24-48 hours before returning to the UK. This is to prevent your pet importing diseases into the UK. A vet abroad will need to sign a certificate to indicate that this treatment has been carried out.
What else do I need to do to prevent worms?
Apart from regularly worming your pets, there are a number of other measures which can stop worms being passed on from dog to dog, or from dog to people.
- If your dog uses your garden as a toilet, clean up the faeces and bury them or put them inside a sealed bag in your dustbin.
- Check your dog for signs of fleas and treat them regularly using the product recommended by your vet. Fleas are more numerous during summer and autumn, 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 dogs. Remember the greatest risk of children being infected with worms is from other children, not your dog.