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Dog Worms and Intestinal Parasites

Roundworms, hookworms, whipworms, and tapeworms are fairly common parasites in dogs. Learn how your dog can become infected, what you can do to prevent infections, what symptoms your dog may show if he is infected, and how to get rid of worms once your dog has them.

Tapeworms in Dogs

The tapeworm sheds its eggs in the feces of an infected animal, and can remain infectious in the environment for a number of months. When a wild animal such as a rabbit eats grass or vegetables infected with the eggs, the wild animal becomes infected, and in turn infects a dog when the dog eats the rabbit. A typical infection may involve as many as hundreds or even thousands of worms. The adult worms then attach to the walls of the intestines and start shedding eggs after about a month.

The eggs can be seen leaving your dog, usually in the feces or stuck to the fur around the dog’s anus. They look like flattened grains of rice that move, and the movement causes the egg cases to shed thousands of eggs too small for you to see.

Roundworms in Dogs

The roundworm may infect the dog when he eats a mouse, rat, mole or some other creature that is infected or a puppy may become infected by worms from the mama either through the uterus or while the puppy is nursing. Roundworms don’t cause huge problems in adult dogs, so you may not even know your dog is infected, but the hormones of pregnancy activate the larvae in the mama dog, causing them to pass through the placenta and into the puppies before they are born.

The roundworms leaves the intestinal tract and travels into other organs, primarily the lungs, where they mature before traveling back to the intestines to lay their eggs. Millions of eggs pass out of the infected dog in his stool, and can live for months. They then develop into infective larvae which can infect other dogs directly, or can infect an intermediate host such as a mouse or mole that a new dog then eats.

Hookworms in Dogs

Hookworms are less common than roundworms, but still cause a problem in the United States, particularly in the south. Hookworm eggs develop into infective larvae which can infect a dog either by passing through the dog’s skin or by the dog eating the larvae. Once the larvae infect a dog, the worms mate, and the female may lay as many as 30,000 eggs each day. The eggs pass out of the dog in the feces, starting the cycle over again. The larvae cannot live in the environment as long as roundworm larvae do, because hookworm larvae die when they are exposed to sunlight. Hookworms do not infect intermediate hosts, so a dog cannot become infected by eating rodents.

Whipworms in Dogs

The eggs from an infected person pass with feces. In the soil, the eggs become infectious in 2 – 4 weeks. When a dog eats something that has contaminated dirt on it, the eggs hatch in the small intestine, releasing larvae that mature into adults and take up residence in the dog’s large intestine. The adult worms attach themselves to the lining of the colon, where they can live for up to a year, with the females shedding between 3,000 and 20,000 eggs every day.

Symptoms of a Worm Infection

Regardless of the type of worm infecting your dog, the worm drains nutrients from your dog’s system, causing his overall health to deteriorate. The dog will often look malnourished, and may develop anemia, which may in turn cause a rapid heart rate. Sometimes, the dog will develop a swollen potbelly, particularly if the infection afflicts a puppy. Puppies may also show changes in their fur, with it becoming dry, coarse, and dull.

Other generalized symptoms include weight loss, fatigue, diarrhea, vomiting, and feces that are unusually dark. More specific symptoms include abdominal pain, which results from the bulkiness of the worms taking up space. In addition, the dog’s nose may be hot and dry, while his gums are pale and his breath is worse than usual.

If you suspect worms, your vet will need to test the dog’s feces for infestation. It is important that you provide a fresh specimen that is close to body temperature and has not been on the ground for very long. However, it is very possible that your dog will test negative even though he is infected with worms. Your vet is likely to prescribe a deworming treatment even if the test is negative because worms are so common in dogs, and because an untreated infection can be so dangerous to your dog.

Treatment of a Worm Infection

No one deworming medication can get rid of every type of worm, but some will treat more than one type. As a general rule of thumb, those medications that are effective against round-shaped worms like the roundworm will not combat flat worms like the tapeworm, and vice versa. If your vet is unsure as to which worm is infecting your dog because diagnostic tests were negative, he may prescribe more than one medication to make sure all bases are covered.

Many heartworm medications also contain deworming agents, so your dog may be receiving treatment without your even being aware of it. Heartgard Plus, Revolution, and Interceptor are all effective against hookworms, but only Interceptor is also effective against whipworms.

How can I Prevent Worm Infections?

Dogs are at an especially high risk of being infected by worms if they live in crowded urban areas or multiple pet households, or if they are used for hunting or show. These dogs should be screened often for worm infections, but for other dogs, twice yearly screenings should be sufficient.

Fleas can carry some species of tapeworms, which can be transferred to a dog. Therefore, flea control can be an important part of your preventive routine.

To the extent possible, keep your dog from eating animal carcasses which may contain worms.

Because worms can live in soil or gravel, consider paving the area where your dog does his business. Clean up after your dog as soon as possible after he defecates. Worms can re-infect your dog, so you want to remove them and their eggs before they have the chance.