Dogs and cats can fall victim to many different types of parasites. Because many of these parasites live in their intestines, veterinarians will take stool samples during your pet’s annual wellness exam to check for signs of intestinal parasites. Intestinal parasites are not uncommon, especially in young animals, which is why wellness exams are so important for maintaining your pet’s good health.


The most common symptoms of these parasites are diarrhea, weight loss, a dull coat, coughing, and fatigue. With some parasites, you may be able to see worms in your pet’s stool, bedding, or under their tail. Puppies and kittens are especially at risk for health complications from intestinal parasites and, in serious cases, these parasites can be fatal. Another risk is caused by some parasitic infections being “zoonotic,” which means that they can be transmitted to humans. These parasites can cause serious health issues in adults and children, including scarring inflammation.

Diagnosis and Treatment

Your veterinarian will take a stool sample to test for the presence of microscopic eggs laid by adult worms. The veterinarian will then mix the sample with a solution that makes the eggs more visible underneath the microscope.

In some cases, a routine stool sample test may be insufficient to diagnose a parasite. For example, detecting the single-celled parasite giardia requires a special solution to be added to the sample. In another case, testing for tapeworm eggs can sometimes cause false negatives. And if the intestinal worms infecting a dog or cat are not mature enough to be producing eggs, the fecal sample test will give negative results–which is why multiple fecal tests over a period of time are sometimes needed to successfully diagnose infection by an intestinal parasite.

After a diagnosis has been made, intestinal worms can be treated by using a dewormer solution. Other types of parasites have require different types of medications to treat. There are some over-the-counter treatments for intestinal worms, but these don’t work very well. Veterinarians have the most powerful and effective dewormers available for treating your pet.


Preventing infection by intestinal parasites is highly dependent on good sanitation practices.

  • Clean up your pet’s droppings as quickly as possible to prevent the spread of infection.
  • Make sure your pet has a source of fresh, clean water, because these parasites can often be found in contaminated water.
  • Prevent your pet from eating soil or grass, which can contain parasitic eggs.
  • Remember that droppings from other dogs might be infested–be sure that your dog doesn’t interact with these while out on walks.
  • Use a monthly heartworm preventative medicine for your pet.
  • Use a monthly flea prevention treatment to prevent parasite transmission to your pets from infected fleas.
  • Don’t allow yourself or your family become infected–wash your hands after playing with your pet and make sure that outdoor play areas for your children, like sandboxes, do not contain any animal droppings.

Types of Intestinal Parasites


The most common type of intestinal parasite, roundworms infect dogs and cats through contact with fecal matter, where the roundworms hatch their larvae. Pets can become infected by roundworms through ingestion of infected soil, licking fur and paws that have come into contact with a contaminated source, drinking contaminated water or coming into contact with cockroaches that carry roundworm eggs.

Roundworms are the most dangerous for young puppies and kittens, because the parasite will drain nutrients away from the pet’s body, which can lead to malnutrition, respiratory issues, and intestinal blockage. Infected female dogs and cats can pass an infection to their young through nursing, but only dogs can pass on their infection in the womb.

Roundworms can also infect humans through ingestion or skin contact. This can cause serious health problems, including organ damage as the larvae enter organs and travel through the body.

Roundworms can lay over 200,000 eggs every day, which makes it very important to catch the infection early before any health complications occur. Symptoms in your pet can include a potbellied appearance, lack of growth, coughing, and vomiting. You may be able to see roundworms in your pet’s stool–they are thin, long and pale.


The second most common intestinal parasite, hookworms are found in dogs and cats, but most commonly in dogs. A pet can become infected by coming into contact with hookworm larvae that enters their body through either their skin or the lining of their mouth. Puppies can become infected by drinking contaminated milk from their mother, but this does not occur in cats.

Hookworms bite into the intestinal lining and drain the blood of their host. This can cause blood loss, weakness and malnutrition, which is especially dangerous for kittens, puppies, and elderly pets.

Like roundworms, hookworms can infect humans through ingestion or skin contact. Ingestion can cause intestinal symptoms, while infection via skin contact can create itching and redness as the hookworm larvae moves through the skin.


Dogs and cats can become infected with tapeworms when they eat fleas, lice or rodents that are already infected by tapeworms.

Tapeworms live in the small intestine and take nutrients away from the food being digested there. This can cause malnutrition in the pet. You may be able to spot tapeworm’s segments in your pet’s stool or backside. They look like grains of rice.


Whipworms are more commonly found infecting dogs than cats. A whipworm infection results from contact with whipworm larvae found in feces, which can occur by eating infected soil or licking contaminated fur and paws.

Whipworms bite into the lining of the large intestine and drain the body of blood. However, they are much less harmful than hookworms and generally do not cause serious health problems. Usually, the only symptoms are weight loss, diarrhea, and blood loss. Whipworms also rarely infect humans. Whipworms look like tiny pieces of thread when found in the stool.


Coccidia is a single-celled organism that can infect cats and dogs through contact with fecal matter containing the parasite. A pet can become infected by eating contaminated soil, drinking contaminated water, or licking paws and fur that has come into contact with infected feces.

After infection, coccidia travels to the intestines and destroys the intestinal lining, which prevents absorption of nutrients. This causes severe diarrhea and dehydration. In some cases, infection can even lead to death.

Coccidia is very contagious to puppies and kittens, so frequently cleaning up feces and frequent changes of water to prevent contamination is especially important around young pets.


Giardia is another single-celled intestinal parasite that can infect dogs, cats, and humans. Infection is caused by ingesting giardia through contact with contaminated food, water, soil, or fur.

Like coccidia, giardia travels to the intestines and damages the lining of the intestinal wall, reducing the absorption of nutrients. Unlike coccidia, infections often have no symptoms. If there is diarrhea, there is usually no blood in the stool.

Diagnosing giardia can sometimes be difficult due to the lack of symptoms and multiple stool samples are needed to confirm the infection because of the specialized tests of giardia.