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  • Morgan F., CVT

Hidden Invaders: Understanding Intestinal Parasites in Cats

Our feline friends can get an abundance of different kinds of parasites inside and out. Here we are going to focus on the most common intestinal parasites in cats. The most common GI parasites are roundworms, hookworms, and tapeworms.


Although not always seen by the naked eye, your cat can pass adult roundworms through their stool or vomit. They are long, thin, and often look like spaghetti noodles. Roundworms are the most common, affecting 25%-75% of cats. Cats become infected by ingesting the parasite eggs while grooming or eating infected rodents. Kittens most commonly contract this parasite by drinking infected milk from their mother.

Cats with roundworms may display symptoms such as vomiting, diarrhea, constipation, or loss of appetite. If a roundworm infection is left untreated, this puts the cat at risk for developing anemia.

Unfortunately, humans can be infected with roundworms. Although rare, this can become serious, especially in children. Roundworms can cause damage to internal organs and the eyes.

Proper hygiene is essential when you have a cat. If people, especially children, put their hands in their mouths after petting an infected cat, they are at risk for exposure.


If your cat is infected with hookworms, you might not see them in their stool due to their small size. Cats become infected with hookworms by ingesting the larvae or if the larvae penetrate their skin often through the footpads. Once inside, the larva migrates to the lungs and then the intestines to mature into adult worms.

Infected cats may show symptoms such as diarrhea and weight loss, which can cause secondary anemia due to blood loss. The infected cat’s stool may be black and tarry due to digested blood.

Humans can also contract hookworms, so again, sanitation is essential. They can penetrate the skin of humans and cause them to develop a skin condition called “cutaneous larval migrans.” This can cause long, linear, track-like lesions that become itchy and irritated.


Tapeworms are long, flat, and resemble tape or ribbon. Cats become infected with tapeworms by ingesting fleas (while grooming) or eating infected rodents. Therefore, if your cat is diagnosed with tapeworms, it is important to treat for fleas as well.

Tapeworms are most commonly known for causing malnutrition in affected cats as they absorb the nutrients the cat ingests. As the tapeworm travels further through the GI tract, little segments break off and can be seen around the cat’s rectum/tail area. The little pieces, called proglottids, are usually white and resemble grains of rice (that stretch and contract when fresh) or sesame seeds (when dried up). Unfortunately, seeing these segments with the naked eye is the most common way to diagnose a cat with tapeworms since fecal examination doesn’t always show the presence of eggs.

As with many other parasites, appropriate hygiene is vital, as humans can be affected by some tapeworm species.


While lungworm may not be as common, it can be tricky to identify so it's worth knowing about! Several roundworm species can cause lungworm. As the name suggests, they affect the lungs and lower respiratory tract, causing bronchitis or pneumonia. Cats get lungworms by eating animals such as lizards, birds, and mice that have eaten infected snails or worms. Lungworms are not passed between cats and cannot be passed to people.

Signs of lungworms may include a persistent cough, labored breathing, and respiratory distress/failure.

Diagnosing lungworm can be challenging as cats may not always pass the larvae in their feces, meaning fecal tests can often be negative even if they are infected. Therefore the diagnosis is usually based on clinical signs, transmission susceptibility, and advanced diagnostics such as bronchoscopy (airway scope), radiographs (x-rays), and failure to improve after medical management with antibiotics.

Intestinal Parasite Management

Prevention is the best treatment! Keeping your cat on reliable parasite prevention year-round can protect your cat. It is also important to get annual fecal samples checked by your veterinarian. There isn’t one treatment that covers all intestinal parasites, so it’s essential to test and know what your cat has so they can get the best treatment. If you have questions, reach our to team at any time for personalized advice.


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