Intestinal Parasites: Dog Worms and Cat Worms

Worms are commonly found in the intestines of cats and dogs. While signs of the disease can vary with the type of worm and the severity of infection, diarrhea is one of the most common symptoms.

How can you tell if your pet actually has worms? Well, sometimes you can't tell. Minor infections of some worms (especially tapeworms) don't really cause too much of a problem for pets, and so occasionally no signs of disease will be seens. Other worms can be more of a problem.

This article will talk about roundworms, hookworms, tapeworms and whipworm. But let's look at each of them individually for a few more details.


These are found in both cats and dogs. They are large worms which can migrate through the lungs before moving to the small intestine, where they feed on tissues. They are mainly a problem in young animals. Kittens and puppies with roundworms usually look pot-bellied. They can also cause diarrhea, dehydration and vomiting, while pets can become malnourished and "fail to thrive". They often have dull, scruffy coats.

"Signs of hookworm infection can include weight loss, pale gums, black or tarry-looking stools, weakness, lethargy and occassionally, death"

In the very worst cases, roundworms can completely block the gut this can be very painful and can potentially lead to death. In other cases, they can cause pneumonia (when migrating through the lungs). Coughing, breathing difficulties, a nasal discharge and weakness or collapse may occur.


These are found in both cats and dogs. Hookworms are much smaller than roundworms, and can also migrate through the body. They reside in the small intestine, but they feed upon blood. Signs of hookworm infection can include weight loss, pale gums (due to anemia from loss of blood), black or tarry-looking stools (due to the presence of blood), weakness, lethargy and occassionally, death.

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Hookworm larvae can enter an animal's body by penetrating through the skin. This causes itchy red swollen tracts where the larvae are migrating. These are most commonlt found in areas where the animal (usually a dog) comes into contact with the ground the feet, chest, belly, ankles or forelegs. This is known as "hookworm pedal dermatitis". In severe cases, it can lead to deformed nails.


These parasites only occur in dogs. They do not migrate through the body, but make for the large intestine, where they burrow deeply into the intestinal wall. This burrowing causes (sometimes severe) inflammation and some bleeding from the gut, although the whipworms themselves do not feed on blood. Occasionally with heavy infestations dogs may suffer from recurrent bouts of abdominal pain and diarrhea, with stools containing blood or mucus. Young dogs or dogs with chronic infection can suffer weight loss, dehydration and mild anemia due to the blood loss.


"Hookworm larvae can enter an animal's body by penetrating through the skin. This causes itchy red swollen tracts where the larvae are migrating."

Tapeworms generally cause little harm or inconvenience to their definitive hosts, usually cats and dogs. Tapeworm infections may cause digestive upsets, itchy backsides and vomiting. Tapeworms can reach several feet long and can potentially cause intestinal blockage, but this is extremely rare.

Animal owners can often detect crawling tapeworm segments in their infected pet's feces or around the anus (looking a little like grains of rice). Infected dogs also often "scoot" (drag their bottom) across the ground or carpet, because tapeworm segments irritate this area. Cats tend to lick their anal area to remove tapeworms.

In order to prevent these problems, it is important to treat cats and dogs regularly for worms. There are many products available for this, with many combining heartworm or even flea treatment with the intestinal worm treatment. Your veterinarian can advise you on the most appropriate treatment for your pet.


1. Kassai T, (1998). Veterinary Helminthology. Butterworth Heinemann, UK.
2. Payne P.A., Carter G.R. Internal Parasites of Dogs and Cats. In: A Concise Guide to Infectious and Parasitic Disease of Dogs and Cats. International Veterinary Information Service, Ithaca, NY.