24/7 Webcam
For Emergencies Call 440.845.7141


Roundworms (ascarids) are the most common intestinal parasite of dogs and cats.  Pets become infected by swallowing roundworm eggs or larvae (immature worms) found in contaminated soil or feces or by eating infected rodents, birds, and certain insects.  Puppies and kittens are commonly infected by the mother while still in the uterus, even if the mother has been wormed herself.  Swallowed larvae travel through the body to the intestine, where they develop into mature worms.  There, adult females deposit eggs, which pass with the stool and develop into infective larvae. 

These intestinal parasites may cause weight loss, weakness, diarrhea, or mucus in the stool.  Mildly infested cats sometimes show no symptoms.

Diagnosis is by identifying the eggs during microscopic examination of a stool sample. 


Public Health Significance

Human infection with roundworm larvae (not adults) is possible but does not occur frequently if good hygiene is practiced, because eating contaminated stool or soil is necessary for infection.  Children should be taught the importance of cleanliness when playing with animals, especially litters of puppies and kittens.  The best insurance against human infection is keeping your pet free from roundworms by regular stool examination and treatment if necessary.


How Common Are They?

  • Roundworms in Cats
    • 1 in 15 cats tested positive for roundworms
    • 21.86% of all positive cases of roundworms in Ohio were in Cuyahoga County.


  • Roundworms in Dogs
    • 1 in 41 dogs tested positive for roundworms
    • 19.11% of all positive cases of roundworms in Ohio were in Cuyahoga County. 

Important Points in Treatment

1. Medication:  For successful treatment, medication must be given as directed.  Call the doctor if you cannot give the prescribed medication.  In some cases, hospital treatment is desirable.

2. A stool sample should be checked 7 days after the last treatment to ensure that all worms have been eliminated.


Control Measures

1. Stool samples should be examined microscopically at regular intervals.  The doctor will advise you regarding the correct times to do this.

2. The stool should be checked for worms before a female pet is bred.  Stool samples from puppies and kittens should be tested at or before weaning.

3. Good sanitation is essential.  Remove stools promptly from the area where your pet is confined.

4. Eggs can remain infective in soil for years, so contaminated ground becomes a source of reinfection. This is especially true of dog pens, runs or areas where your pet may be tied.  Control measures for these areas include:

  • Turning the soil over to a depth of 8 to 12 inches after your pet is free of worms.
  • Replacing dirt runs with concrete, which seems to be the most effective control procedure.
  • Removing stools daily.
  • Moving your pet to a new, uncontaminated area.

Related Articles

Fecal Testing
My pet has worms. Can my family and I also get worms? What should I do?