Intestinal Parasites in Cats and Dogs…Should You Be Worried?

Dr. Claire McPhee

Common Intestinal Parasites
Keeping your pets healthy requires consideration of what may be happening inside. Intestinal parasites are commonly seen on routine fecal tests. While many patients have clinical signs of gastrointestinal upset, other parasitic infections can be sub-clinical.

We are fortunate in beautiful Bellingham that many internal and external parasites are less common than other areas of the state and country, including heartworm disease and many tick-borne diseases. However, we see a large number of internal parasites that are easily preventable.

Regular parasite control is important, particularly since several parasites are potential sources of zoonosis, causing disease in humans. Dogs can become infected by close contact with the feces of other dogs, or in some cases cats or other animals.

What are they?
The three most common intestinal parasites in cats and dogs are roundworms, hookworms and whipworms.

Roundworms – Toxocara species
This parasite is extremely common in animals less than one year old, but can cause disease throughout life. This parasite only requires ingestion of a few infective eggs. The eggs can remain in soil, such as from parks or playgrounds for many years – which is why it is so important to pick up feces as soon as possible. Toxocara spp. are common causes of zoonotic disease, primarily in children due to ingestion of larvated eggs. In humans, migrating toxocara larva can cause a number of serious diseases affecting the liver, lungs, central nervous system and the eyes. The best way to prevent disease in your pets and in humans is to prevent shedding of the eggs since they are so hearty. In 2016, more than 3% of canine fecal samples from Whatcom County tested positive for roundworms.1

Hookworms – Ancylostoma species
Dogs and cats become infected with these parasites after ingestion of infective larvae from the environment, skin penetration, nursing, or consuming rodent tissue. These intestinal worms can cause blood loss that can be significant in young animals. Hookworms can also cause disease in humans, and the larvae are able to migrate into the skin. The best way to prevent disease in your pets and in humans is to prevent eggs hatching into infective larvae by cleaning up feces promptly and avoiding bare skin contact with contaminated areas. In 2016, more than 3% of canine fecal samples from Whatcom County tested positive for hookworms.1

Whipworms – Trichuris species
Animals are infected by consuming eggs from the soil. Many infections do not result in clinical disease, but severe cases can result in bloody diarrhea, weight loss, dehydration, anemia, and rarely, death. Infective eggs can persist in the environment for many years. It can take up to 3 months after infection before a fecal sample identifies whipworm eggs. Fortunately, whipworms are not known to cause zoonotic disease. In 2016, about 0.5% of fecal samples from dogs in Whatcom county tested positive for Trichuris.1

Tapeworms – Dipylidium caninum
Various species are prevalent and infection typically via ingestion of fleas or contaminated host. Can be a zoonotic, although rarely causes serious human medical concerns.

Credelio for dogs, a monthly flea and tick preventive, paired with Interceptor Plus, a deworming medication, will eradicate all four types of intestinal parasites. Revolution for cats, a monthly topical flea preventive also treats for roundworms and hookworms.-stock up during our spring promotion April 1st-30th!
– Annual fecal tests for prompt identification of parasite infection – or more frequent for high risk animals (indoor/outdoor cats, dogs that go to day care, dog parks, or other areas with large numbers of dogs)
– Clean up feces within 0 – 2 days
– Wear shoes and gloves when gardening
– Children’s sandboxes should be covered when not in use.
– If a fecal analysis is positive, we can also treat with an oral deworming medication. Treatment should always be confirmed with another fecal sample approximately 1 week after to ensure that the infection has been cleared.


[1] Companion Animal Parasite Council