Intestinal Parasites in Cats & Dogs

Intestinal parasites are worms and single-celled organisms (protozoa) that can exist in the digestive tract of dogs and cats. They can infect animals of any age, although puppies and kittens tend to be the biggest victims. Intestinal parasites vary in size and shape, and some are so small they must be diagnosed by antigen testing or microscopic evaluation. Others, like roundworms and tapeworms, can be visible in feces. Certain intestinal parasites are contagious to other animals and humans. Parasites attach themselves to the lining of the intestines. They suck blood and nutrients from food the animal has ingested. The result is damage to the intestinal lining and malabsorption of nutrients from food. Other parasites are passed to puppies or kittens through mother’s placenta or milk. Infected animals may show no signs of infection, while others may suffer from diarrhea, weight loss, malnutrition, weakness, and blood loss. There are dozens of varied species and types of intestinal parasites, but only a few types that result in most of the parasitic infections in dogs and cats.

What are the most common intestinal parasites affecting dogs and cats?


Known as nematodes or ascarids, these are the most common intestinal parasites in dogs and cats. Adult roundworms are 3-5 inches long, cream-colored, and tubular shaped. Animals with roundworms pass the infection to other animals when the worm eggs develop into larvae and are present in the infected animal’s feces. The larvae then inhabit the soil around the feces, leaving other animals (and children), vulnerable to accidental ingestion. In addition to diarrhea and weight loss, animals with roundworms can also exhibit a “potbellied” appearance, coughing, and the presence of worms passed in the feces. Diagnosis is made through the detection of roundworm eggs in feces using a microscope.


This is the second most common intestinal parasite found in dogs, but they are less common in cats. These are dangerous parasites in that they bite into the intestinal lining and suck blood. Pets also become infected when larvae penetrate the animal’s skin or the lining of the mouth. Puppies are more vulnerable to infection than adult dogs; infected mothers pass larvae through their placenta, colostrum or milk.  Severe cases can cause anemia and pneumonia. Diarrhea with dark, tarry feces signals internal bleeding and often accompanies severe infections. Diagnosis is made though identification of hookworm eggs in feces using a microscope.


This parasite's name is inspired by their whip-like shape. They are more common in dogs than in cats. Adult whipworms are typically found in the colon and cecum (large intestine) of the animal. Eggs are passed in the feces and become infective in about 4 to 8 weeks. Once infective eggs are ingested, larvae develop in the small intestine and move to the colon where the adults mature. Whipworms bury their heads in the lining of the intestine and suck blood, but they are less harmful and do not cause health problems. Often, there are no clinical signs of light infections, but if not diagnosed and treated in a timely manner, an increase in the number of worms results in intestinal inflammation, followed by diarrhea, weight loss, and blood loss. Whipworm eggs remain viable in soil for years.


Also known as cestodes, tapeworms are segmented worms that get their name from their thin and flat appearance. Dogs and cats become infected when they eat infected fleas or lice. Animals that have access to small mammals (i.e., rodents) infected with these worms are also at risk. It is important to note that since tapeworm eggs do not show up well in routine fecal analyses, your veterinarian should be notified if you see rice-like segments near your pet's tail.  In addition to common symptoms associated with parasitic infection, a shaggy coat, and colic may be present. There may be no signs in mild cases.


These are single-celled parasites (protozoa) that are not visible to the naked eye. Like many intestinal parasites, coccidia are very contagious among puppies and kittens as their immune systems might not yet be strong enough to fight off the infection. Dogs will show signs of infection more often than cats. Treatment may be unnecessary in cats because they usually eliminate the infection themselves. Pets become infected by eating infected soil or licking contaminated paws or fur. Bloody, watery diarrhea may be present, with the potential for dehydration. The presence of coccidia is detected through a routine fecal test.


Like coccidia, giardia is a single-celled protozoan that attaches and multiplies in the small intestine, damaging the intestinal lining and reducing the absorption of nutrients from food. They produce cysts that pass through the feces. The cysts survive well in the environment and only a small number of organisms are needed to cause infection. As a result, Giardia is harder to diagnose than other intestinal parasites, and several stool samples may have to be tested before it is found. Giardia infection sometimes shows no clinical signs in dogs or cats. In more severe cases, it can cause weight loss and diarrhea, abnormal feces (soft, pale and foul-smelling), and vomiting.

    How are parasite infections treated?

    Conventional treatment uses deworming medication. Medications like pyrantel can produce side effects including nausea, vomiting, lack of appetite and diarrhea. Side effects of other common medications include dizziness, cough, dark urine, and black tarry stools. These side effects mimic the symptoms of the infection themselves, making it difficult to differentiate between a symptom of the infection and a medication side effect. Do your research on the chemicals used in recommended products including dosage and instructions for use, as well as side effects.

    There are safe and natural remedies for deworming your pet. They can be used to treat an active infection as well as prevent one.

    Fruits & Vegetables

    Fruits and veggies that are high in fiber (carrots, banana, apple, coconut, and papaya) act as natural de-wormers. Grate them into your pet’s bowl. Dosage is 1 tsp per 10 pounds body weight. Fermented vegetables are a great natural de-wormer—in addition to boosting the immune system, they can also help expel the parasites. Pomegranate is useful for eliminating tapeworms.


    Pumpkin seeds contain an amino acid called Cucurbitin that paralyzes the worms and eliminates them from the digestive tract. Serve ¼ tsp per 10 pounds of ground seed once or twice daily until the parasites are gone. Black cumin seeds (whole) are safe and effective for most worms. Use ½-1 tsp daily in food. Heat the seeds in a pan to get rid of the bitter taste.


    For use in dogs in moderate amounts: dosage is ¼ clove per 10 pounds body weight daily. Chop the garlic and let it sit for 10-15 minutes before adding it to your pet’s food. Do not use garlic to fight worms in pregnant or lactating dogs. 

    Apple Cider Vinegar

    Can be used in both dogs and cats. It creates a more alkaline digestive system that’s less attractive to parasites. Use raw organic, unfiltered ACV and give ¼-1 tsp in your pet’s water or food.


    Herbs like thyme and parsley are natural de-wormers. Thyme is especially useful for hookworms. Add one tsp per pound of food. Cook fresh parsley down, strain out the solids, and freeze them into ice cubes. Give one cube daily.

    Natural Pet De-wormer Products

    Homeopathic remedies, essential oils, and other natural pet de-wormer products can be powerful additions to your pet’s regimen. Be sure to purchase from a reputable company and read the reviews of the product before purchase. 

    Food Grade Diatomaceous Earth (DE)

    Add in ¼ tsp for small dogs up to 1 tsp for dogs over 55 pounds. DE actually rids the body of roundworms, whipworms, pinworms, and hookworms within 7 days of being fed daily. But to be most effective, it must be fed long enough to catch all newly hatching eggs or cycling of the worms through the lungs and back to the stomach as DE does not kill the eggs.

    Can parasitic infestations be prevented?

    The short answer is YES! A pet’s strong immune system can keep parasite infections under control. Parasites tend to proliferate in weak, sick, stressed and neglected animals. A species-appropriate diet is the best line of defense to prevent parasitic infections. Keep your pet’s immune system strong by adding mushroom powderstinctures, antioxidants and probiotics to their daily nutrition regimen.

    Sanitation is important, especially in kennels or catteries where large numbers of animals are housed. Feces should be removed and disposed of frequently, and fecal contamination of feed and water should be prevented. Runs, cages, and utensils should be disinfected daily. Insect control is also important. Pet parents should employ their own good hygiene and wash hands after handling their animals. 

    Be sure your veterinarian includes annual fecal testing as part of your pet’s annual examination. Fecal samples should be checked more frequently if your dog or cat prefers to spend most of its time outdoors. A fecal test on a fresh sample should be performed following treatment of an infection to make sure all parasites have been cleared.

    Even though in most cases, intestinal parasitic infestation is not a life-threatening situation, it can lead to various clinical problems. If left untreated, it can become a public health issue. Deworming is an important preventative care regime for reducing parasites and improving your pet’s health. Fruits, vegetables, seeds, herbs and homeopathic extracts are all great natural alternatives to prescribed deworming medications. Keep your pet’s immune system at optimal health, and parasites won’t find a welcoming environment!

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