7 Ways Dogs Can Get Worms

The risk of parasitism by worms in dogs is, unfortunately, quite common. Most parasitic worms will reside in a dog’s intestinal system. The most well known exception is the aptly named heartworms, which live within the heart chambers, the pulmonary artery, and surrounding vessels. There are several ways your dog may become a host to worms but, thankfully, there are things you can do to minimize your dog’s risk. Here are the most common ways your dog can become infected with worms.

Ways Dogs Can Get Worms

Contaminated Soil

Intestinal worms work by passing their eggs in the stool of their hosts. When a wild animal infected with intestinal worms leaves behind scat, the parasitic eggs present can contaminate the soil. Some worms can even persist in the soil for years. If your dog likes to eat things in the yard or chew on sticks, they can become infected with any parasites that may be present. Dogs may become infected with roundworms, hookworms, or whipworms this way.

From Their Mother

Certain intestinal worms can actually be passed from mother to puppy via the mother’s milk. Roundworms and hookworms can be passed in this manner. Roundworms can also be passed in utero, meaning they can be transmitted to the puppies while they are still in the womb. This occurs through placental blood flow.

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Contaminated Water

Reasons humans should avoid drinking pond water holds true for dogs as well. In addition to bacteria that can cause leptospirosis, contaminated water may also contain single-celled organisms such as giardia and coccidia that can cause vomiting and diarrhea.


Literally meaning the act of eating stool, dogs can contract intestinal worms by consuming infected stool. This can be stool from wild animals in their yard or on walks, stool from other dogs or cats in the home, or even their own stool, reinfecting themselves with the worms they already have. Roundworms, hookworms, and whipworms can be contracted this way. The worm eggs in stool take days to weeks to develop into infectious larvae, so prompt cleaning can help prevent reinfection.


Another way your dog can become infected with intestinal worms is by hunting and eating wild animals already infected by worms. A dog can become infected with hookworms, whipworms, and tapeworms this way.


Although fleas are a parasite in and of themselves, they can also be a source of transmission for intestinal worms, namely tapeworms. If your dog accidentally ingests a flea while grooming themselves, they can become infected by any tapeworm larvae in the gut of the flea.


Known for being vectors for multiple diseases, mosquitoes can also transmit heartworms between, not just dogs and cats, but coyotes, foxes, and other mammals. Fortunately for you and me, our immune system is better equipped to recognize and kill off heartworm larvae before they can mature into adult worms and cause real problems for us.

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How to Prevent Your Dog From Getting Worms

It may seem like worms are simply lying in wait to infect your dog, but preventing them can be almost as simple.

Flea and Heartworm Prevention

Monthly flea prevention can not only help prevent a flea infestation in your dog, but it can also lessen your dog’s risk of getting a tapeworm. If there are no fleas on your dog to begin with, they can’t accidentally ingest a flea and potentially pick up a tapeworm. There are a variety of commercially available topical products and even a couple of oral products that prevent fleas. Certain products can be purchased over the counter, at pet supply stores, big box stores, and even online stores. If you are not purchasing directly from your veterinarian, ensure that you are using the correct dosage for your dog’s weight. Also ensure that you are using flea prevention intended for dogs for your dog.

Never use dog flea prevention on cats and never use cat flea prevention on dogs; at best, the prevention will be ineffective. At worst, you may cause irritation, burns, and even neurological symptoms.

There are different kinds of heartworm prevention on the market. Most are still oral chews that are given monthly, but there is one variety that is applied topically every month and another product that is given as an injection at your dog’s veterinary office either every 6-12 months. The word “prevention” is bit of a misnomer when it comes to heartworm prevention because it works more retroactively than proactively. When you give your dog its heartworm pill on the first of the month, the medication actually kills all the heartworm larvae your dog was exposed to in the previous month. There are different larval stages of heartworm, though, and the monthly preventions don’t kill all of these stages. This is why it is imperative that your dog’s heartworm prevention be given on time every month and not every other month, etc.

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An added bonus with oral heartworm prevention is that most also prevent roundworms and hookworms. Some even prevent whipworms. While this is a definite benefit and way to prevent intestinal worms, the duration of efficacy for prevention of those worms may not be the full 30 days that it is for the heartworms. The injectable form of heartworm prevention can kill off any hookworms your dog may have at the time of injection, but this product has no long-lasting effects for intestinal worm prevention. The topical form of heartworm prevention, unfortunately, does not prevent or treat intestinal worms in dogs at all.

Routine Stool Checks

Keeping up with routine stool checks is a must. Most veterinary offices recommend checking a stool sample every six to 12 months. If your dog happens to be on a heartworm prevention that doesn't provide any intestinal parasite protection, your vet may recommend more frequent stool checks to screen for any possible parasite infections.


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About the Author: Tung Chi