Roundworms and You. Yes, YOU!

Roundworms are among the most common parasites seen in dogs and cats. That is because they are sneaky. Roundworms are often spread by eating infected stool or other items in the environment that have be previously covered in infected stool but that isn’t all. As part of their lifecycle the worm larvae migrate through the liver and the lungs of infected dogs. Some of the larva hide out in the muscles of female dog during their migration and become dormant (encyst).  In the dormant stage no drug currently known can kill them. When the female dogs get pregnant the dormant worm larvae wake up and can re-infect mom and actually cross the placenta to infect puppies. This is why we are most likely to see round worm infections in young animals.

Symptoms of round worm infections can include weight loss, poor coat, a potbellied appearance (particularly in young animals), vomiting and diarrhea. If that is not bad enough, the sneaky worms that infected unborn puppies hide in the liver and lungs until birth. When the puppy is born they get active again and can do cause extensive damage to the lungs. Sometimes the puppies die a few days after birth.

Roundworms can affect human heath too. If a round worm egg gets into a human and hatches, the larva begins to migrate just like it would in a dog or cat. It can cause organ damage to the liver particularly but others as well. Occasionally the larvae end up migrating in an eye and causing blindness or in the brain and causing brain damage.  Young children are at higher risk than adults because they are less aware of hygiene and tend to put their hands in their mouth more often. Also children have a less developed immune system. When you have small children and I ask you to do a fecal exam on your pet this is what I am most worried about.

There are a few testing options for roundworms. The traditional fecal float that has been available for years detects eggs shed by adult worms. This is very helpful and will pick up many infections. It is not able to detect younger worms that have not started shedding eggs yet and adult worms that do not happen to be shedding eggs that day.  The newer test available is actually able to test for roundworm DNA so it is able to detect early infections and infections not shedding eggs.  This newer test is a bit more costly but well worth the extra especially recommended for puppies and dogs that have vomiting and diarrhea.

There are many inexpensive of options for roundworm treatment. If your dog is on a monthly heartworm preventative they may already have some protection from roundworms. However, no treatment will kill all the larval stages. This means that if an infection is present it WILL take multiple treatments to get rid of all the round worms. After we do 2-3 treatments we will ask you to bring in a fecal sample to make sure there is no indication that more worms are present.  During treatment for a parasite infection or whenever you have adopted a new pet young or old we recommend picking up stool immediately from the yard and never letting it sit in the environment where it has the potential to re-infect your pet or infect your family.


This worm was vomited up by a 3 month old puppy.

About the Author

Dr Elizabeth LaytonView all posts by Dr Elizabeth Layton
Dr Layton graduated from the Ontario Veterinary College in 2005 and began work in mixed animal practice. Dr. Layton’s special interest is dentistry but she enjoys a variety of internal medicine and surgical cases.


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