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

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

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What are worms in dogs?

Worms are a colloquial term for parasites that live inside dogs or other animals and need a host 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 worms commonly seen in dogs include roundworms, hookworms, whipworms, tapeworms, and heartworms. Each of these worms has a different lifecycle with different hosts and different modes of transmission. 

How do dogs get worms?

Parasites are transmitted to dogs in a variety of ways. Depending on the worm’s life cycle, it 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 insects, such as fleas or mosquitos, that transmit parasites when in contact with your pup.

Others may be 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.

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Type of worms in dogs

There are several different types of worms that dogs contract. It can be useful if you learn a bit about the most common ones. 

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 larvae, 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 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 it 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 onto the intestines. These worms look like the stuff of nightmares but, luckily, are only one centimeter long and can be easily treated with the proper medications. They infect dogs in some 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 enter through their skin and migrate to the intestines. Dogs with hookworms may have no symptoms but can 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 to the intestines, they can also cause respiratory signs such as coughing, difficulty breathing, or itchy skin. These are also considered a zoonotic risk in that people can be infected by larvae in the environment that enter bare skin.

Whipworms

Whipworms are another intestinal parasite with 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, weight loss, decreased appetite, cause your dog to strain when they poop, 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) when they 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.

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. Early in the infection, there are no symptoms, but in untreated cases when the numbers of worms multiply, dogs can develop symptoms including coughing, difficulty breathing, fatigue, collapse, and even death.  

Heartworms are most common in places with warm weather all year, where mosquitoes thrive, such as in the Southern U.S. However, heartworm infections have been diagnosed in dogs in all 50 states, and all dogs are potentially at risk. 

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How can you tell 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 differ from these kinds of worms since they mainly live in blood vessels in the heart and lungs. This parasite usually will not cause noticeable symptoms until the infection is severe. In those cases, the signs may include coughing, shortness of breath, collapse, or even death.  

How are worms diagnosed in dogs?

There are several 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 in their body. Many parasites do not cause visual changes in dogs. Still, your vet may notice a distended belly, gas-filled intestines, tapeworm segments around the anus, or abnormal heart and lung sounds.  

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 the 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. 

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Treatment for worms in dogs

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. 

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 number 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.

When to call your vet for worms

If you see worms on your dog, particularly around the anus, or in vomit or diarrhea, it is important to call your vet. It is also a good idea to have your vet run a fecal test if your dog has been around other dogs you know have worms. In addition, it is smart to have your dog in for a vet visit at least once yearly, which should include a fecal exam. 

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How can you prevent worms in your dog?

There are many effective ways to prevent worms in dogs, and you can strategically reduce your dog’s risk of infection by thoroughly understanding 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 preventing tapeworm infections from Diplidium caninum. Some of these preventatives also contain medications that will kill intestinal parasites, 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 much time outside or live with many other dogs may be more prone to intestinal parasites. They may benefit from routine deworming because they could spread the infection to other dogs, even if they don’t have symptoms.

Good hygiene practices are 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. 

References:

• Ames, Marisa K., and Clarke E. Atkins. “Treatment of Dogs with Severe Heartworm Disease.” Veterinary Parasitology, vol. 283, May 2020, p. 109131, https://linkinghub.elsevier.com/retrieve/pii/S0304401720301114

• Seah, S K, et al. “Dogs and Intestinal Parasites: A Public Health Problem.” Canadian Medical Association Journal, vol. 112, no. 10, 17 May 1975, p. 1191, pmc.ncbi.nlm.nih.gov/articles/PMC1959112/

• ‌Traversa, Donato. “Pet Roundworms and Hookworms: A Continuing Need for Global Worming.” Parasites & Vectors, vol. 5, no. 1, 10 May 2012, ‌https://parasitesandvectors.biomedcentral.com/articles/10.1186/1756-3305-5-91