There are many types of intestinal parasites that can infest cats and dogs; common intestinal worms of dogs and cats include tapeworms, roundworms, hookworms, and whipworms. While worms can cause a range of symptoms, most can be effectively treated. Different areas of the world see different "common" regional parasites and some areas (notably the dry and arid climates) see few problems with intestinal parasites.
Symptoms of Worms in Cats and Dogs
Roundworms, tapeworms, hookworms, and whipworms are quite different from one another; only roundworms are easy to spot. Hookworms and whipworms are so tiny that they're essentially invisible to the naked eye, while tapeworms are slightly larger and roundworms are much easier to spot.
In some cases, pets have no symptoms at all from intestinal worms. In other cases you might see:
- Weight loss
- Dry fur
- Breathing problems
- Itching, especially the paws
- Pale gums
- Slow growth and weakness
- Breathing difficulties
Roundworms can also affect humans, and, left untreated, can cause serious illness. Because worms are usually carried by fleas and ticks which carry other serious diseases, it's very important to address parasites at their source by removing fleas and ticks from your home.
Causes of Worms in Cats and Dogs
Roundworms are often introduced to kittens and puppies in utero: they are actually born with an infestation inherited from an infested mother. Mothers can also pass along roundworms through their milk. Roundworms live in their hosts' intestinal tracts and can grow to be as long as five inches. Eggs laid by the roundworms are excreted in the host's feces and can be picked up by other animals in the environment. Roundworm larvae can also be breathed into human lungs and will find their way to human intestines.
Hookworms are very similar to roundworms but are much more common in dogs than in cats. Because they consume a good deal of blood, they can actually be deadly to young puppies.
Tiny whipworms are very hard to find because they are tiny and produce few eggs. They live in the host's intestines and are most prevalent in settings where a number of dogs or cats congregate (kennels and catteries). A dog that is failing to thrive may be treated for whipworm based on the possibility of an infestation. Hookworms can also be passed along to human beings, and can cause severe skin issues.
Tapeworms are segmented worms that can often be seen in a pet's fur or around its anus. These common parasites require multiple treatments, and can only be eradicated with prescription drugs available through your vet.
Treatment for Worms in Cats and Dogs
Of the four worms mentioned above, only one, the tapeworm, generally requires one deworming treatment. This is because the roundworm, hookworm, and whipworm infections require one dose to kill the adult worms living in the intestine and a second dose to kill the migrating larval forms of the worm. The adult worms will often be seen in the pet's feces after a deworming.
The tapeworm does not have an intermediate internal migrating larval form like the round, hook, and whipworms do and thus does not require the second treatment. Tapeworm dewormer medication removes the tapeworm's protective coating and essentially dissolves the tapeworm and the eggs inside of it with one dose.
Tapeworms are not typically seen in the feces after a deworming, though tapeworm segments are often seen exiting the anus in pets that have tapeworms. Pets that have a large load of tapeworms may vomit up tapeworms.
Treating Roundworms, Hookworms, and Whipworms
Roundworms, hookworms, and whipworms each have a slightly different life cycle, but they all produce migrating/developing larvae that require a second dose of dewormer to kill these new developing worms. For roundworms and hookworms, a second dose is needed in 3 weeks (and sometimes another dose in a few more weeks), for whipworms, the second dose is at 73-75 days.
Roundworm and whipworm eggs are notoriously long-lived in the environment. Hookworm larvae live in sandy soil, a potential reinfection hazard for pets and a human health hazard for people who contact the infected soil. Sandboxes are particularly problematic because pets and other animals tend to use them as "litter boxes;" it's a good idea to completely change the sand in a sandbox and cover the box daily to avoid infection or reinfection. Tapeworms are transmitted most commonly by fleas (Dipylidium caninum) but can also be transmitted to dogs by rabbits (Taenia pisiformis) and to cats by rats and mice (Taenia taeniaeformis).
Preventing Worms in Cats and Dogs
A basic preventive method involves removing all feces from your yard and your cat's litter box as often as possible (at least once a week). Be careful to avoid animal feces in other areas (the dog park, for example).
Some monthly heartworm preventives will take care of intestinal worms as well as heartworms, but it's important to consult your veterinarian for the best medication choice for your pet and your situation. Some veterinarians recommend a second tapeworm deworming, in cases of flea-transmitted tapeworm infection, to allow the owner time to address the flea problem in the home, in the outdoor environment, and on the pet. If your pet develops worms more than once, your pet may also suggest a regular deworming regiment.