✔️Article written by a veterinarian & reviewed by Dr. Whittenburg, Director, on Dec 5th, 2022.
When cleaning up the yard, you found some worrying white strings in your dog’s poop. Many types of intestinal parasites can affect dogs. Some may be seen in poop, while others cause symptoms without ever being seen. In this article, we will focus on worms found in dog poop: how do you know you’re seeing worms and not something else? And how do you know which type of worms are in your dog’s poop?
When to call your veterinarian
There are a few indicators that you should schedule an appointment for your dog:
- You see worms in the poop – this one is obvious. Worms are not a normal finding, so your dog needs medication.
- Rounded belly
- Diarrhea, soft stool, or blood in the poop
- Dull, lackluster coat
- Poor growth, weight loss
Which worms do we commonly see in dog poop? (with pictures)
The appearance of intestinal parasites in your dog’s poop/stool will depend on the type of worm.
Let’s review the most common types of worms found in dog poop (with pictures):
1. Roundworms (estimated 35% of cases of worms seen in dog stools)
Roundworms are the most commonly found intestinal parasite in our canine companions; many dogs will have them at some point in their lives. Roundworms are especially problematic in puppies, although adult dogs can also get them. Roundworms look like thick pieces of spaghetti. They can be a few inches long, as shown in the picture below:
Below are two pictures of roundworms in a dog’s poop (stools). Roundworms tend to be about the thickness of a pencil (or slightly smaller) and long like this:
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The two most common species seen in dogs are Toxascaris leonina and Toxocara canis. These worms feed off partially digested food in the intestines, diverting essential nutrients from dog to worm. Puppies seem to be most affected since they tend to have weaker immune systems than adult dogs.
Roundworms can be passed from infected to uninfected dogs in several ways. One way they are passed is from a mother to her puppies. When a pregnant dog is infected with roundworms, (or she has encysted larvae in her body from a previous infection), she can pass the larvae stage of the roundworm through the placenta to the developing puppies or through milk when puppies are nursing. It is critical to have your vet deworm any pregnant dogs and puppies, even if you haven’t seen worms in their stools.
When roundworm eggs are passed in the stools, Toxascaris is infective within a week and can live for many months. Toxocara eggs are passed into the stool, but take up to a month to mature and become infective; with these roundworms, fresh feces are NOT infective, but the contaminated soil will be.
Symptoms of roundworms:
- Poor or stunted growth in puppies
- Weight loss
- Potbelly appearance
- Worms in stool
- Worms in vomit – less common unless roundworm infection is severe.
Learn more about roundworms in dog poop.
2. Whipworms (est. 34% of cases of worms seen in dog stools)
Whipworms look like thread and often taper to a smaller point at one end. Whipworms are significantly smaller than other worms, topping off around 1/4 inch, with very few up to an inch long.
Trichuris vulpis is the whipworm that commonly infects dogs; it lives in the dog’s large intestine and buries its head into the intestinal mucosa, feeding on the dog’s blood supply and causing severe inflammation. Eggs are passed in the dog’s stool and become infective over the next 2-4 weeks. So like roundworms, the contaminated soil is infective, but not the newly passed feces.
Below is a picture of what whipworms in a dog’s poop look like:
Female whipworms intermittently shed small numbers of eggs, meaning the eggs may not always be seen on a fecal test when looking for parasites, even if the dog is infected; this often leads to a false negative. Often, vets treat dogs with chronic diarrhea with a broad-spectrum dewormer if an intestinal parasite is suspected but not seen on the fecal test.
A large infestation of whipworms may show the following symptoms:
Disclaimer: This content is not a substitute for veterinary care. Always consult with your vet for health decisions. Learn more.
- Watery, bloody diarrhea
- Weight loss and decrease in body condition overall
3. Tapeworms (est. 14% of cases of worms seen in dog stools)
Tapeworms are not often seen in complete worm form. Usually, owners will notice individual tapeworm segments that look like a single grain of rice. These may be around the dog’s anus, sticking to the surrounding fur, or even in the dog’s bed.
Below is a picture of tapeworms in a dog’s poop:
Proglottids contain tapeworm eggs and can be typically seen near the anus or on fresh dog poop, as showcased in the picture below:
Watch it live in action – on dog’s poop – with this short video from Veterinary Parasitology:
Remember that you will probably also need to treat your dog (and home and environment) for fleas. Even after treatment, dogs can immediately reinfect themselves with tapeworms if infected fleas are still in the environment.
Tapeworms are flat, segmented intestinal parasites that pass their eggs in segments called proglottids. These segments look like rice grains. Often we don’t see the entire tapeworm passed in our dog’s stool, but the proglottid segments are visible in stool or around the dog’s anus and fur.
The life cycle and transmission of the tapeworm are closely tied to fleas, so flea prevention is vital in preventing tapeworms. Consequently, tapeworms are more likely to infect dogs that live in areas with heavy flea populations.
So how does your dog get tapeworms? Typically your dog transmits tapeworms by ingesting an infected flea, but occasionally by eating an infected rodent or bird.
Serious side effects of tapeworms are rare. Usually, the owner only notices them because they find the segments in the stool, on the dog’s back end, or in bedding. The dog may scoot on the ground or bite at his back end to relieve the skin irritation from the tapeworms.
Dogs need to be treated with a prescription medication called praziquantel to get rid of tapeworms. This medication starts working immediately to dissolve the tapeworms; typically, dead worms aren’t seen in the dog’s stool because they are dissolved and digested in the dog’s intestines.
Hookworms are tiny – often only 1/8″ long – so they are not usually “seen” in dogs’ stools. They have tiny hooks on their mouth, usually only seen when the worm is viewed under a microscope.
Hookworms are some of the smallest intestinal parasites that affect dogs but can have a significant negative impact on the dog’s health. They can be especially deadly to puppies, causing so much internal blood loss that they need a blood transfusion to survive.
Hookworms attach to the small intestine via their hook-like mouths. They feed on blood and can cause significant internal blood loss. They can pass through ingestion, skin, and from the mother to puppies via placenta and milk. Hookworms can penetrate the skin through the feet or belly. Dogs can also ingest them when they lick their feet.
Most hookworms stay in the small intestine throughout their life cycle, but a few larvae will migrate through tissues into the trachea and lungs. The dog then coughs up larvae and swallows them, sending the hookworm larvae back into the intestines to complete their life cycle.
Symptoms of hookworms include:
- Pale gums
- May or may not have diarrhea
- Severe blood loss, sometimes requiring transfusion
- In older dogs, it can be more chronic, with weight loss and anemia
Hookworms are common in areas of poor sanitation and overcrowding, especially in areas of warm, moist climates.
Signs that your dog has intestinal parasites
Your dog may be infected with intestinal parasites without you seeing the worms in the poop. Some other symptoms commonly seen with intestinal parasites include:
- Soft stool or diarrhea, sometimes with flood
- Failure to thrive and potbelly appearance, especially in puppies
- Weight loss
- Dull coat
- Changes in appetite and energy
Is it intestinal worms, or is it something else?
Typically, worms in the poop are pretty obvious. There are a few things veterinarians see that may mimic worms, however.
- String – While this is more common in cats that play with and eat string, your dog can chew a string and pass it in large pieces in the poop.
- Rice or other undigested food – Undigested rice often has a tapeworm-like appearance. Some owners will notice this when their dog has been eating a bland diet of rice and chicken following an upset stomach.
- Chewed-up toy or bone – Much like a string, a chewed-up toy or pieces of bone could mimic a worm.
- Maggots in poop – Poop that has been left outside for long periods can occasionally develop maggots. Flies lay their eggs in the dog’s stool that is in the yard; these eggs then develop into larvae.
Veterinary treatment, costs & recovery
Vets recommend fecal tests 1-2 times yearly to check for intestinal parasites. You can take a small, fresh sample of stool to your vet’s office; you only need a few tablespoons for the test. Typically fecal tests can be done in-house, meaning your vet runs the test right there, and you get results that day (often during your appointment. A standard fecal test costs between $15-40. Often, more advanced fecal testing, which looks for the DNA of parasites, will be performed by sending the feces to a lab. This is much more accurate as there may not be a worm egg in every small sample of feces, and it typically costs $50-80.
Treatment costs will vary widely by the size of your dog, the type of medication required, and how many doses your dog needs to clear the worms. A general range is $35-50.
Your veterinarian will have a variety of dewormers that can treat a roundworm infection. Many heartworm medications now cover multiple types of worms as well. Tapeworms are one of the few intestinal parasites that often need a different, specific medication not included in routine dewormers.
Most dewormers will start to work within hours, but it may take a few days for all the worms to clear. Because the worms are often killed and digested in the intestines following treatment, you won’t always see worms in your dog’s poop after treatment.
After treatment, it is important to do another fecal test to ensure there are no lingering worms.
How to prevent intestinal worms in the future
Parasite prevention is relatively easy with your local veterinary clinic’s routine fecal tests and deworming treatments. There are no foolproof steps – with routine dewormers, dogs can still contract intestinal parasites from places like parks, daycares, and boarding, even from the yard through infected soil or feces.
Your veterinarian may recommend a routine dewormer depending on your region and the fecal test results. Many monthly heartworm medications also protect against numerous intestinal worms as well. Do not give over-the-counter deworming products – there has been some evidence of resistance to these medications, meaning they may kill some of the parasites your dog has but leave behind resistant ones.
Are these worms transmissible to humans?
Yes, all of these parasites are transmissible to humans – for example, roundworms can cause permanent blindness in humans.
What can you do at home to help prevent parasites?
Picking up feces soon after your dog has gone out helps prevent environmental contamination. By picking up feces, your dog is less likely to be re-infected, either from their own infected poop or that of other dogs. It is also essential to protect your dog with prevention in the form of heart worm preventatives. These medications will continually deworm your dog and prevent an infestation. Flea control is also important.
Prevalence of common canine gastrointestinal nematodes in the USA
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