Intestinal Parasites (WORMS!)

Summer Safety Series: Intestinal Parasites (WORMS!)

Ever thought about what it would feel like to have worms living in your intestines? Most of our dogs or cats could tell us, since these parasites are extremely common especially in puppies or kittens. The mother cat or dog can pass on parasites while the animal is developing in the uterus, they can ingest them in the milk, or when they are exposed to their parent's feces.

With adult dogs, intestinal parasites can be easily picked up from the park when a dog either sniffs or licks another dog's feces, the area where another dog's feces has been, or contaminated water sources like puddles. Cats are more likely to pick up these parasites from another cat's feces, or from eating rodents. These parasites can also be acquired from many other sources such as sniffing or licking another animal's rear end, eating the intestines of deceased rodents, or ingesting fleas (this is common!), just to name a few. We recommend sending away our pet's feces at least yearly for parasitic testing, since many of these parasites are microscopic and cannot be seen with the naked eye. Here are some of the more common intestinal parasites we see on a daily basis.

Roundworms (Nematodes or Ascarids)

These spaghetti like worms live freely in the intestinal tract, feeding on partially digested intestinal contents. The roundworm eggs are excreted into the feces, where they can be ingested by other animals sniffing or licking feces or the infected soil in the environment. It takes about one month for eggs shed in the environment to become infective when ingested.

What you see with your eyes: Rarely with a dog or cat you may see the adult worm in stool or vomit.


Giardia is a protozoan parasite picked up through ingesting contaminated water, soil, or feces. It has a sucker on its belly, helping it stay adhered to the inside walls of the intestines of our dogs and cats. The sucker is also what makes it Giardia one of the most stubborn parasites to treat.

Many parasites can be acquired from ingesting feces, but this one especially can be transmitted to people from their animals, it is zoonotic. With any disease, especially one which is zoonotic, remember to wash your hands after petting your animal. Many pets will lick their anus after defecating to keep it clean, then can lick our hands or face. There is always a risk of ingesting parasite eggs if we don't wash our hands after handling our pets, especially just before eating.

What we see under the microscope: The parasite, just like in the picture above.

What you see with your eyes: Occasionally we will see intermittent diarrhea, often stools will look normal unless the infection is more severe.


These flattened worms are acquired from eating fleas, or eating rodents such as mice or rats. Tapeworms can grow up to 10 inches long in the intestines! They eat the food we eat, then shed segments of themselves just like a small purse containing thousands of eggs. Unless the segments open in the fecal sample, sometimes we can't see these eggs under the microscope. With any animal who has had multiple fleas, when they bite at themselves, they often ingest the fleas, which releases the tapeworm eggs.

What you see with your eyes: Tapeworm segments around the animal's anus or in the feces.
If your pet goes hunting, bring in their feces for testing more often than once yearly. Remember they can pick up parasites at any time. Many of these parasites are easily found on a fecal sample and can be treated with deworming products. Give us a call if you have a question about parasites or would like more information about these worms.

Practice information

South Windsor Animal Hospital

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