Types of Worms in Dogs: How to Detect and Treat Worms in Dogs

Worms are a generic term for a variety of creepy parasites that can infect your dog, other animals, and sometimes humans, too. Many of these parasites live in the intestines, but some can migrate to other parts of the body as well. These worms have all kinds of weird ways to live inside dogs and other critters. Some cause almost no symptoms at all, while others can make them very sick. Learn all about these stealthy hitchhikers and how to diagnose and treat them. 

How do dogs get worms?

Parasites are transmitted to dogs in a variety of ways. Depending on the worm’s life cycle, they may live in an intermediate host that then comes in contact with dogs or other animals. These intermediate hosts may be prey that they eat, such as mice, snails, or fish, or they may be insects, such as fleas or mosquitos that transmit parasites when in contact with your pup. Others may be present in the environment and come into contact with your pup that way. Each one is unique in its lifecycle and habits, but one thing they have in common is that they are bad news for your pup and you want to steer clear of them.

What are worms?

Worms are a colloquial term for the kinds of parasites that live inside dogs or other animals and need a host in order to survive. Typically, they cannot live outside of a host animal and mooch nutrients and other necessities from their host while causing some degree of damage or inconvenience to their host’s body.  Some of the worms that are commonly seen in dogs include roundworms, hookworms, whipworms, tapeworms, and heartworm. Each of these worms has a different lifecycle with different hosts and different modes of transmission. 

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How do you know if your dog has worms? 

You may or may not be able to detect if your dog has worms because some cause symptoms while others do not. Some may not cause symptoms until the infection is severe. In general, intestinal parasites may cause symptoms related to the digestive tract, including diarrhea, gas and bloating, vomiting and/or weight loss. In animals with large amounts of worms, there could even be worms visible in the vomit, or segments of worms visible in their poop. Heartworms are different from these kinds of worms since they mainly live in blood vessels in the heart and lungs. This is a parasite that usually will not cause obvious symptoms until the infection is severe. In those cases, the signs may include coughing, shortness of breath, collapse, or even death.  

Types of Worms in Dogs

Roundworms        

Roundworms are one of the most common intestinal parasites in dogs, especially puppies. This worm’s life cycle includes eggs shed in the environment that are ingested by a host animal. Dogs can be infected, either by eating small mammals that are already infected with larva, ingesting eggs directly from the environment — or most commonly — from their mothers when they are nursing.

Many dogs with roundworms show no signs of the infection, but if they do, the common signs are a bloated belly, poor weight gain, diarrhea and/or vomiting with worms visible in the vomit. This is considered a zoonotic infection, meaning it can be transmitted to humans. In most cases when humans get roundworms, it is from direct exposure to the eggs in the environment, such as in a sandbox, garden, or from ingesting contaminated food. It would be very unusual for a human to get roundworms directly from a dog, but is another good reason to practice good hygiene and wash your hands and clean up thoroughly after your dog poops.

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Hookworms

Hookworms are appropriately named, given the sharp teeth they use to hook on to the intestines. These worms look like the stuff of nightmares but luckily are only one centimeter long and can be easily treated with the right medications. They infect dogs in a number of creatively horrible ways, including if they eat prey like cockroaches, when larvae are directly ingested in the environment, through milk when puppies are nursing from an infected mother, or when larvae enters through their skin and migrates to the intestines. Dogs with hookworms may have no symptoms at all, but can also show gastrointestinal signs, including vomiting, diarrhea, or weight loss.

Because of the sharp teeth they use to attach to the intestines, hookworms cause a lot of damage to the lining of the intestines, and this can result in bleeding which may lead to anemia, blood in the poop, or even ulcers. When these worms migrate through the body on their way to the intestines they can also cause respiratory signs like coughing and difficulty breathing, or itchy skin. These are also considered to be a zoonotic risk in that people can be infected by larvae in the environment that enter bare skin.

Whipworms

Whipworms are another intestinal parasite of dogs, and they have no intermediate hosts. The eggs are shed directly into the environment and are then ingested by other dogs. This worm takes up residence in the large intestine or colon, where it causes a lot of inflammation. This can lead to diarrhea, straining to poop, weight loss, decreased appetite, and/or anemia. Because these eggs are transmitted directly from the environment, it is important to clean up thoroughly after your dog (or other dogs) poop and to make sure dogs are not housed in moist environments where the eggs can survive.

Tapeworms

Tapeworms may be transmitted in different ways depending on the species, and these worms also establish themselves in the intestines. One species of tapeworm, known as Dipylidium caninum, uses fleas as an intermediate host, so dogs tend to become infected by accidentally ingesting fleas. This is common when dogs have a flea infestation because they chew and bite at their skin since the fleas are so itchy, accidentally ingesting some fleas along the way.

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The species of tapeworms, known as the Taenia species, use other mammals as intermediate hosts in their life cycle, so dogs are infected if they eat contaminated prey. Tapeworm infections are almost always silent, meaning dogs do not show any symptoms at all; however, occasionally they may have mild gastrointestinal signs and/or itchiness around their anus as they shed segments of the worms. These segments may also be visible around the butt or in the poop and look similar to grains of white rice. 

Heartworms

Heartworms are infamous for the risks they pose to dogs. You may have even seen one of those terrifying photos of a dog’s heart filled with spaghetti-like worms in your vet’s office. These worms are different from all the others on this list because they are transmitted by mosquitoes and then migrate through the blood vessels to the heart and lungs. Heartworm is most risky in places with warm weather all year, where mosquitoes thrive, such as in the Southern U.S. But heartworm infections have been diagnosed in dogs in all 50 states and all dogs are potentially at risk. Early in the infection, there are no symptoms, but in cases that go untreated and the numbers of worms multiply, dogs can develop signs including coughing, difficulty breathing, fatigue, collapse, and even death.    

How are worms in dogs diagnosed?

There are a number of different ways to diagnose worms and sometimes multiple tests are necessary to confirm a diagnosis.

The physical exam is the first tool your vet will use to look for signs of a parasite infection. Your vet will thoroughly examine your pup from head to toe, listen to their heart and lungs, and feel for any abnormalities on their body. Many parasites do not cause visual changes in dogs, but your vet may notice a distended belly, gas-filled intestines, tapeworm segments around the anus, or abnormal heart and lung sounds.  

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Vets will often recommend a fecal exam for dogs showing signs consistent with intestinal parasites; this may also be part of a routine annual check up. To perform this test, you will need to bring a fresh poop sample to your vet. There are a number of different tests that can be performed to check for parasites, and the most common one is called a fecal flotation in which the sample is processed to look for eggs that are shed in the poop. Different parasite eggs look very distinct so if the eggs are present, the diagnosis is easy. However, due to different life cycles of these worms, eggs are not always present in a single poop sample even if the dog has parasites. It is possible to have a false negative and may be worthwhile to submit additional samples if your dog’s symptoms persist. 

Blood tests are the main way to test for heartworm disease in dogs. An in-house antigen SNAP test is usually part of a routine annual check up, and may be performed more frequently if warranted. This is a basic screening test, and if this test comes back positive, additional tests are performed to confirm the diagnosis. Blood tests are not as useful in diagnosing intestinal parasites because they do not test for specific parasites. A dog with intestinal parasites may have certain changes in their blood work such as signs of anemia or elevated white blood cells called eosinophils, but these findings are not specific to one kind of parasite. 

Treatment

For intestinal parasites, treatment is fairly straightforward with the right dewormer combined with a thorough cleaning of the environment. Most dewormers are medications that can be given by mouth, and there are specific drugs that target different parasites, so an accurate diagnosis is important. Because many of these parasites can re-infect their host if they are present in the environment, it is very important to thoroughly clean up all poop, both inside and outside the home. Also, make sure all fabric and hard surfaces are properly disinfected. It is also a good idea to wipe your dog’s hind end and paws after they poop or play outside to reduce the chance of them re-infecting themselves. 

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Heartworm treatment is more complicated in that the worms are in a vital part of the body and in the process of killing them, they can cause complications for their host. Depending on how long your dog has been infected and the numbers of worms likely to be present, your vet will consider different treatment strategies. This may include a combination of medications given by mouth with a series of injections given over many months. During treatment, it is very important to restrict your dog’s exercise because they are at higher risk of complications from exerting themselves.

How can you prevent worms in dogs?

There are many effective ways to prevent worms in dogs and you can strategically reduce your dog’s risk of infection with a thorough understanding of how these worms are transmitted. Many monthly preventatives include drugs to prevent fleas, ticks, and heartworms. These can be very effective in the battle against heartworm and should be used year-round. Preventing fleas has the added benefit of also preventing tapeworm infections from Diplidium caninum. Some of these preventatives also contain medications that will kill intestinal parasites as well, making them a very effective way to keep your pup healthy.

Regular deworming is another strategy that may be useful, depending on your dog’s risks and exposures. Dogs who spend a lot of time outside or live with many other dogs may be more prone to intestinal parasites. They may benefit from routine deworming because they could be spreading the infection to other dogs, even if they don’t have symptoms.

Good hygiene practices are always an excellent way to keep your pup healthy and prevent illness. When it comes to worms, this includes discouraging your dog from eating wild prey or other materials found outside, avoiding contact with sick dogs and wild animals and their poop, cleaning poop up quickly, and disinfecting appropriately. 

Can you deworm your dog yourself? 

If your dog is on a monthly preventative, you may be deworming your pup already without realizing it. This is a routine way to prevent most intestinal parasites and heartworms from getting comfy in their new host. If you are concerned that your dog has an active infection, it would not be a good idea to try to deworm them yourself without consulting a veterinarian. This is because different drugs are effective against different parasites, and if you don’t know which one is making your dog sick, you may very well use the wrong medication. Over-the-counter medications are not always safe for all dogs, and the dosing should be based on your dog’s specific weight to ensure they get the right amount of medication.  

Worms are a part of dog life that tend to make people squirm and itch, but knowledge is power when it comes to parasites. The more you know, the better armed you will be to prevent, identify, and treat any worms that come your pup’s way. 

Resources:

American Heartworm Society: Heartworm Basics
What Every Pet Owner Should Know About Roundworms and Hookworms