Common Intestinal Parasites in Pets


At Lawndale Veterinary Hospital, we recommend fecal sample testing in dogs and cats at least annually, even if there are no gastrointestinal problems. The fecal test is a great way to identify intestinal parasites that may (or may not) be causing symptoms in your pet. Today, we want to give you insight into five of the more common intestinal parasites we tend to diagnose in the clinic.


Coccidia is a protozoal parasite that can infect the intestinal tract and cause diarrhea in dogs and cats. The organism tends to be species-specific (so there are coccidia species that infect cats, and other coccidia species that tend to infect dogs). Sometimes we might even see an unexpected coccidia species (e.g. bird coccidia) in a pet’s stool that has no clinical signs. Can you guess why? It’s probably because this pet ingested some bird stool recently and the bird coccidia is just passing through the pet’s system.

Coccidia is most often seen in young animals, stressed animals, or those with compromised immune systems. In addition to medications for symptomatic animals, environmental sanitation and minimizing stress are also important things to consider.


Roundworms are the most common intestinal parasite found in dogs and cats.

Dogs: Many puppies are born with roundworms. They can also acquire the roundworms through the mother’s milk or by ingesting infectious eggs from a contaminated environment. Dogs may also become infected if they eat small mammals (e.g. mice) that have the roundworm larvae in the tissues.

Cats: Kittens can acquire roundworms through the mother’s milk. Like dogs, cats can also become infected by ingesting infectious eggs from a contaminated environment, or by ingesting small mammals that have the roundworm larvae in the tissues.

Once in the intestinal tract, the roundworm feeds on the food the animal eats. Heavy accumulations (especially in puppies or kittens) can cause death. Roundworm larvae can encyst in muscle tissue and then reactivate during times of stress for the animal. Females can lay as many as 200,000 eggs per day.

Symptoms of a roundworm infection can include: Vomiting, diarrhea, poor growth, weight loss, or a pot-bellied appearance. The worms can sometimes be visualized by owners as spaghetti-like worms in the stool. Note that many animals infected with roundworms are asymptomatic (e.g. they do not show any signs of the infection).

Roundworms can be zoonotic.


Dogs: Dogs can acquire hookworm eggs through contaminated environments (fecal-oral route), larval penetration of intact skin, ingesting a small vertebrate host infected with the hookworm larvae, by eating a cockroach containing the infective larvae, or through transmammary transmission (nursing).

Cats: Cats can acquire hookworm eggs through contaminated environments (fecal-oral route), larval penetration of intact skin, ingesting a small vertebrate host infected with the hookworm larvae, or by eating a cockroach containing the infective larvae.

The hookworm attaches to the lining of the intestinal wall and feeds on the blood of the pet. Animals can develop anemia from the blood loss, and severe infections can lead to death (especially in puppies and kittens). Female hookworms can potentially lay 30,000 eggs per day.

Symptoms of a hookworm infection might include: Inappetance, vomiting, diarrhea, pot-bellied appearance, and anemia. Again, note that many animals infected with hookworms may not display symptoms.

Hookworms can be zoonotic.


Whipworm eggs can be acquired by a dog from a contaminated environment (fecal-oral route). While females can lay 2,000 eggs per day, eggs may only be shed intermittently. This fact makes diagnosing a whipworm infection potentially more difficult.

Symptoms of a whipworm infection in dogs can include: Diarrhea, bloody diarrhea, anemia, anorexia, and abdominal pain. Note that dogs may also be asymptomatic.


The tapeworm species (Taenia sp.) most commonly seen in veterinary clinics are transmitted when an animal ingests an infected flea. There are also other tapeworm species (Diphyllobothrium sp. and Echinococcus sp.) that can infect dogs and cats when the pet ingests wildlife that is infected with the tapeworms.

Tapeworm eggs are difficult to diagnose in fecal samples. Often, a Taenia sp. tapeworm infection is diagnosed by the owner visualizing ‘rice-like’ segments in the stool or on the pet’s hind end. If your pet has had fleas, keep in mind that they are then also at risk for a Taenia sp. tapeworm infection. If your pet has tapeworms, then you should be looking for fleas!

Although less common, Taenia sp. can be zoonotic. The Diphyllobothrium sp. and the Echinococcus sp. tapeworms are certainly a zoonotic risk.

With intestinal parasites in general, environmental cleanup is critical for minimizing intestinal parasite exposure risk. This is true for your pet, and in the case of zoonotic intestinal parasites, for people as well. Many parasite eggs can live for years and years in the environment, making a contaminated area a source of infection (or re-infection) for years to come. Take care to clean up your pet’s stool as soon as your pet eliminates to help reduce risk and contamination.

Furthermore, pets who hunt small mammals or ingest cockroaches may also be at an increased risk of acquiring certain intestinal parasite infections. And remember, using year-round preventive medications can help protect your pet against certain intestinal parasites. Sentinel protects dogs against roundworms, hookworms, and whipworms (in addition to heartworm and flea egg protection). Revolution protects cats against roundworms and hookworms (in addition to heartworm, flea, and ear mite protection).

Is it time for your pet’s fecal test? Your pet will appreciate it if you bring a fresh sample when you come for the appointment (versus us having to obtain the sample in the clinic). Give us a call today to schedule your pet’s fecal check!

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Author: Dr. C. Noureddine, DVM, MS