What are Roundworms and Why Should I Care?

What are they?

Roundworms are the most common intestinal parasite in dogs and cats. The adult worms are round and range in size from less than two inches to almost 6 inches in length. According to the Companion Animal Parasite Council, a survey conducted in 1996 using samples collected from across the United States found that more than 30% of dogs younger than 6 months of age were shedding roundworm eggs and other studies have shown that virtually all pups are born infected. Other surveys have found more than 25% of cats infected.

How does my pet get roundworms?

Because the larval stages of the worms migrate inside the animal, some of the worms become encysted and lie dormant in the host animal’s organs. When the female becomes pregnant, those hidden parasites can become active, mature, and be passed to the puppies or kittens across the placenta before they are ever even born. Sometimes the worms pass into the mother’s milk so the young ones are exposed again when they are nursing. Cats and dogs can also become infected by licking and/or eating grass and dirt and other soiled items that contain infective eggs or by eating prey animals that have already been infected.

Puppy RunningWhat disease does it cause in my dog or cat?

The migrating larvae travel through the body causing damage primarily to the liver and the lungs with most of the clinically significant damage occurring in the lungs and resulting in coughing and respiratory problems. Once adult worms form in the gastrointestinal tract, your puppy or kitten may develop vomiting, diarrhea , bloating and abdominal discomfort.

Can my pet give the worms to me?

Roundworms are not transmitted between people to other people. And they are not directly passed from dogs and cats to people. Affected dogs and cats shed eggs in their feces. The eggs mature into the infective stage of the parasite in the environment and are then swallowed with dirt that is either eaten on purpose (pica) or inadvertently (through inadequate care and hygiene). The infective larva do not progress to adult worms in people but the migrating larvae leave the intestines and find their way to other organs such as lungs, liver, or eyes and cause damage and disease in those locations.

Note that wild animals, especially raccoons, commonly carry roundworms and can also be a significant source of environmental contamination in places where they share outdoor areas with us and with our pets. Human infection with raccoon roundworms can be especially serious so do not feed or otherwise encourage raccoons around your home.

What diseases do roundworms cause in people?

People are not the definitive, natural host for roundworms which means that the roundworm lifecycle is not completed in humans. We do not develop adult worms. In infected people, it is only the immature, migrating larvae that produce the illness. Fever, abdominal pain, difficulty breathing can occur as larvae move throughout various organs and systems in the body. If the larvae travel to a person’s eyes, their presence can cause inflammation and redness and even blindness.

According to the Centers For Disease Control approximately 14% of people in the United States test positive to antibodies against roundworms. That does not mean that those people have significant, clinical disease but it does mean that at some point in time those individuals were exposed to roundworm larvae which resulted in their bodies producing antibodies in an effort to clear the infection.

Cat Looking Out WindowHow is a roundworm infection treated?

In people roundworm larvae infections are often self limiting since the worms cannot undergo their complete life cycle in humans. If illness does occur, as can be the case especially in young children, your physician will decide on the best course of treatment given the particular circumstances.

In pets, there are many products that are safe and effective in treating roundworm infections.

Since so many puppies and kittens are already infected at birth, it is very important that all of them are given appropriate worming medication at 2, 4, 6 and 8 weeks of age. Likewise all new pets (regardless of age) should receive treatments as soon as possible. The goal is not just to try to avoid infection but also to stop the shedding of eggs in the stool before they contaminate your environment and become an ongoing source for infection for your pets and your family.

Better yet, how do I prevent roundworm infections?

A single adult, female roundworm can lay hundreds of thousands of eggs in one day; and the eggs are very difficult to kill in the environment and can survive for years. Remember, however, that the eggs that are shed in the feces are not yet capable of causing infection. Depending on environmental conditions, it can take 1 to 4 weeks or so for that development to occur. Therefore, be diligent about cleaning up after your pets. Dispose of all feces promptly - at least once a week.

Wash your hands and your children’s hands frequently - after handling pets, pet waste, gardening/working in the soil, or playing in sand boxes/playgrounds. Wash vegetables well to remove any dirt, do not let your children eat dirt, and discourage your pet from hunting.

And see your veterinarian for parasite testing and to discuss appropriate products for year round prevention and control of parasites in order to protect your pets and your family.

 If you have any questions or concerns, you should always visit or call your veterinarian – they are your best resource to ensure the health and well-being of your pets.


Beware the Bug

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Cryptosporidium in Dogs, Cats and People

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Reviewed on: 
Friday, March 31, 2017