Based on an article that first appeared at

If you’re a pet owner, you know that deworming is an important step in your dog or cat's preventive care protocol. But what exactly are you preventing?

Typically referred to simply as “worms,” there are four main types of intestinal parasites that are common in pets—and they’re not just creepy, they’re harmful. Here’s what to watch out for.


Hookworms are tiny intestinal parasites named for the hook-like mouth parts they use to attach to the intestinal wall. Pets may become infected with hookworms through the mouth, skin, the mother’s placenta before birth, or the mother’s milk after birth.

Pets often become infected when they swallow hookworm larvae, or immature worms, through routine grooming or ingestion of soil or other contaminated substances in the environment. The larvae may also penetrate the skin and migrate to the intestine to mature and complete the life cycle.

If a pregnant dog has hookworms, the pregnancy may reactivate larvae. These larvae will enter the female's circulation and pass to the puppies through the placental blood flow. Finally, puppies may become infected through the mother's milk. This is a common route of infection for young dogs.

Once your pet is infected, the hookworm attaches to the lining of the intestinal wall and feeds on his blood. Its eggs are ejected into the digestive tract and pass into the environment through your pet’s feces, potentially increasing exposure to other animals. (Source)

In dogs, a large number of hookworms can cause anemia. This problem is most common in puppies, but it will occasionally occur in adult dogs.

Hookworms also are parasites that people can acquire from the environment, but generally don't infect the gastrointestinal tract, but we can get infected through the skin. Read about all the details in the 'Worms and Germs'  site about hookworms.

A major source of roundworm infection for puppies and kittens is the mother's milk.Roundworms

Roundworms are one of the most common intestinal parasites found in dogs and cats. Unlike hookworms, they do not attach to the intestinal wall. Instead, they live in the intestines and consume partially digested food. Once your pet is infected, roundworms pass tiny eggs into his stool.

A mother dog or cat who has had roundworms at any time in the past can transmit them to her puppies or kittens before birth. This is true even if the mother tests negative for roundworms because the larvae (immature worms) encyst in the mother's muscle tissue and are not detected by our tests for adult worms.

Another major source of roundworm infection for puppies and kittens is the mother's milk. Roundworm larvae may be present in the mother's mammary glands and milk throughout the nursing period.

Pets may also become infected by swallowing roundworm eggs, which contain infective larvae. The larvae hatch out in your pet's stomach and small intestine and migrate through the muscle, liver, and lungs. After several weeks, the larvae make their way back to the intestine to mature. When these worms begin to reproduce, new eggs will pass in your pet's stool and the life cycle of the parasite is completed.

Roundworm eggs passed in another animal's stool may be infectious to your pet. In fact, a large number of animal species have been found to harbor roundworms and represent potential sources of infection for dogs and cats, including cockroaches, earthworms, chickens, and rodents.


Tapeworms are long, flat worms that attach themselves to your pet’s intestines. A tapeworm body consists of multiple segments, each with its own reproductive organs, which are passed in your pet’s feces. Tapeworm infections are usually diagnosed by finding these segments—which often resemble white grains of rice or seeds—in your pet’s stool, on his rear, or where he lives and sleeps. (Source)

Tapeworm segments do not pass every day or in every stool sample; therefore, inspection of several consecutive bowel movements may be needed to find them. We may examine a stool sample in our office and not find them, but you may find them the next day. If you find them at any time, please contact us so we may provide the appropriate treatment.

In order to become infected with tapeworms, your pet must ingest a flea that contains tapeworm eggs. This process begins when fleas are accidentally ingested upon licking or chewing the skin. The flea is digested within your pet’s intestine and the tapeworm hatches, anchoring itself to the intestinal lining. It is important to note that any exposure to fleas may result in a new infection that can occur in as little as two weeks.


Whipworms are parasites that live in the cecum (where the small and large intestine meet) and colon, where they cause severe irritation to the lining of those organs that can result in watery, bloody diarrhea and weight loss. Whipworms can be one of the most harmful worms found in pets if not properly treated.

Whipworms pass microscopic eggs in the stool. Pets become infected by ingesting these eggs in soil or other contaminated substances in the environment. Whipworm eggs are very resistant to drying and heat, allowing them to remain viable in your pet’s environment for years. Once laid, the eggs mature to an infective stage and reinfect within 10 to 60 days. When the eggs are swallowed, they return to the lower intestinal tract to complete the life cycle.

It is important to remember that your pet may remain susceptible to reinfection after treatment, particularly if he goes outdoors. What Are the Signs?

Intestinal parasites are typically not visible to the naked eye and most infected pets will still appear to have normal stool. Instead, pets infected with worms may experience diarrhea, vomiting, abdominal pain, or weight loss. You may also notice your pet has a dull coat or pot-bellied appearance.

How Are Worms Diagnosed and Treated?

The microscopic examination of a stool sample will usually help us to determine the presence of intestinal parasites. Fecal exams are recommended for all puppies and kittens and should be repeated annually in adult pets to allow for rapid diagnosis and treatment if parasites are present.

Even if a fecal exam is not performed, your veterinarian may recommend the use of a deworming product that is safe and effective against several common parasites. We do this because our deworming medication is safe and because worms do not pass eggs every day, so the stool sample we have may not detect worms that are really present.

After the initial treatment, deworming should be repeated in about three weeks. It is important to repeat this treatment because the deworming medication only kills adult worms. Within three to four weeks, the larval stages will have become adults and will need to be treated.

It is important to remember that your pet may remain susceptible to reinfection after treatment, particularly if he goes outdoors. If this is the case, periodic deworming throughout your pet’s life may be recommended.

How Are They Prevented?

To protect your pet and family from parasites, follow these steps:

  • Deworm puppies and kittens appropriately as recommended by your veterinarian. Nursing females should also be treated to avoid reactivating infection.
  • Deworm your pet any time parasites are detected on a fecal exam. Periodic deworming may be appropriate for pets at high risk for reinfection.
  • Dispose of feces immediately, especially in yards, playgrounds, and public parks. For cats, stool should be removed from litter boxes daily.
  • Exercise strict hygiene practices. Do not allow children to play in potentially contaminated environments.
  • Don’t skip your pet’s annual fecal exam. Pets with predatory habits should have a stool sample checked several times a year.
  • Keep your pet flea-free. It is important to keep all pets in your household on a consistent flea control regiment to prevent the development of flea eggs and intestinal parasites. For dogs and cats with a current flea problem, we recommend also using an adulticide.

Does your pet need a parasite check? Contact us or schedule an appointment today!



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