Worms in Dogs

CONFIRM THE WORM

Dogs are a parasitic worm’s quintessential host, largely due to the fact that canines easily pick up diseases and infections as they explore the environment with their mouths.  Worms or larvae that are sitting in trash, feces, or dirt, can quickly be transferred to a dog.

Most parasitic worms are species-specific, however some worms found in dogs can also be transferred to humans.  Contact with contaminated soil or feces could potentially lead to accidental infestation, resulting in eye, lung, heart, and neurological problems.  It is important to learn about the different types of parasitic worms in dogs, and how to protect yourself and your family in the event that your pet becomes ill.

The most common worms in canines include tapeworm, heartworm, lungworm, roundworm, hookworm, and whipworm.  These worms are all considered parasites because they require a host in order to survive. The worms benefit from deriving nutrients from a dog’s body, and will begin to grow and multiply once ingested.  This proliferation of worms can eventually be fatal if left untreated. All of these types of parasitic worms display different symptoms, however several common warning signs for intestinal worms, excluding heartworm, are as follows:

Transmission

There a several different ways that a dog can pick up a parasitic worm, such as rolling in, eating, or stepping in soil or feces that contains worms or worm larvae.  Worms often live in animals like birds, rodents, and reptiles, so eating any of these animals could also result in a transfer of the worm host.  Additionally, mosquito, flea, and tick bites can cause a spread of infectious worms, and puppies can get worms by drinking their mother’s contaminated milk while nursing.

Some infestations do not present any symptoms, and can even remain dormant in a dog’s body until he or she is under immense amounts of stress such as during the later stages of pregnancy in females.  The activation of worms in pregnancy causes the parasites to infect puppies in utero, or they can be passed through the mammary glands in the mother’s milk. If left untreated, worms can cause severe illness and lead to death.

Identifying which parasite your dog has can be tricky, as many worms are microscopic and cannot be seen with the naked eye.  Below you will find detailed information on behaviors your dog may be exhibiting, as well as characteristics about each worm.  Remember, your veterinarian is the best resource if you think that your pet might have a parasite, and routine check-ups are vital to keeping your dog in good health.

When Should My Dog Get Tested?

Heartworm: All dogs should be tested annually for a heartworm infection.  This testing can be done during a routine checkup.  If your dog has missed a checkup or a vaccine dosage, you should take your dog into the vet to get tested immediately, and then tested again six months later.  It takes at least six months for a dog to test positive for heartworms after it has been infected.  Annual testing should always be done, even when a dog is on heartworm prevention year-round.  This is to make sure that the prevention is working, because although heartworm medications are highly effective, a dog can still become infected, even if your dog only misses one dosage.

Intestinal Worms:  According to the Companion Animal Parasite Council (CAPC), all animals should receive a preventive physical exam at least every 6 to 12 months.  Fecal examinations by centrifugation should be conducted at least four times during an animal’s first year of life, and then at least two times per year thereafter.  Learn more about fecal centrifugation and parasite testing on our Dog Treatment and Prevention page.

 

Roundworm for dogs

roundworms in dogsRoundworms are the most common worms found in dogs, and they live in a dog’s intestines where they eat partially digested food that the animal has consumed.  Stealing the dog’s food and nutrients can lead to malnourishment, and puppies are at a greater risk because their immune systems have not quite fully developed yet.  Unfortunately, it is very common for puppies to be born with roundworms. They contract the parasite from their mother in the uterus during gestation, and the larvae (juvenile form of the worm) are also transmitted through nursing.

Additionally, if a dog has ever contracted roundworms, they can remain dormant in the body for years and even a lifetime.  If a female dog becomes pregnant, the dormant parasites can become reactivated and be passed down to her young. These larvae can also remain in the female’s body and make her sick again (American Kennel Club, 2015).

Appearance

Roundworms are usually white or light brown, a few inches long, and look like spaghetti.

Contraction

Eggs in the stool of infected dogs are left behind and then ingested by another dog.  The eggs can also be left in soil and plants in the environment. Roundworm eggs can be transported by other small animals, including rodents and birds.  They are not the typical roundworm host so the egg never matures in these animals, however if a dog eats one of these infected animals, the egg can be transported to the pup and grow into a roundworm in the dog’s intestines.

Symptoms

Some dogs can be infected by the roundworm parasite and will not show any signs of illness, however, most dogs that have a major infestation will exhibit digestive signs such as diarrhea, vomiting, and a distended gut.  In some cases, there may also be respiratory symptoms as the immature worms pass through the lungs, resulting in coughing and pneumonia.

Dangerous to Humans?

The roundworms that impact canines do not complete their life cycle in humans, however they can still make humans very ill.  If a human accidentally ingests the eggs of the roundworm, for example, if a child accidently gets dirt in their mouth, the eggs can turn into larvae that become enclosed in a cyst in the organs of the body which can cause extreme illness.

To learn about the treatment and prevention of worms, check out Dog Treatment and Prevention.

Hookworm for dogs

Hookworms are intestinal parasites that actually hook themselves into the lining of a dog’s intestinal wall.  There are three stages in the lifecycle of the hookworm: egg, larvae, and adult. The larvae can survive for weeks or even months before they migrate into the dog’s intestines where they infect the dog, become adults, and lay more eggs (American Kennel Club, 2016).

Appearance

Hookworms get their name from their mouths that are shaped like hooks, which attach to the intestinal lining.  They feed off of the little blood vessels, and they are about 0.3 centimeters in length.

Contraction

Hookworm can be transferred if a dog eats contaminated dirt or feces in the environment, or drinks soiled water.  While in the contaminated dirt, the larvae can also burrow into a dog’s skin if the animal is rolling around in it.  Grooming of a dog’s paws can cause accidental ingestion if the worm gets stuck in the fur.  Much like other parasitic worms, a mother can pass hookworms down to her puppies in the uterus, or through her milk while nursing.

Symptoms

  • Failure to gain weight or weight loss
  • Loss of appetite
  • Diarrhea
  • Anemia
  • Bloody or tarry stools
  • Coughing, due to the larval migration through the lungs (with very heavy infections)
  • Pale gums
  • Weakness
  • Itchy paws
  • Poor growth
  • Death

Dangerous to Humans?

Adult hookworms cannot infect humans, however the larvae can tunnel itself under a person’s skin and into the human body, causing extreme itching known as “ground itch.”  Once the larvae have made their way into the body, they can be very dangerous as they penetrate and damage internal organs and the eyes, potentially causing blindness. These conditions are very rare, and can be prevented by avoiding contact between skin and moist soil.  Shower regularly and wash your hands frequently.

To learn about the treatment and prevention of worms, check out Dog Treatment and Prevention.

Whipworm for dogs

Whipworms live in the cecum and large intestine in a dog’s body, where they attach to the mucosal lining, a membrane that lines many cavities in the body and covers the surface area of several organs.  Adult whipworms lay eggs in the large intestine, which are then passed through the dog’s stool, and into the environment to pick up another host after 10-60 days. The eggs mature to an infective-state in the environment, and once ingested, they will hatch and further mature in the lower intestines, where they attach to continue the cycle (American Kennel Club, 2017).

Appearance

Whipworms are ¼ inch-long organisms, with a thick anterior end (the handle of whip) and a long, thin, posterior end that has a characteristic whip-shaped body (lash of the whip). The anterior end implants into the intestinal wall as the worms mature, causing irritation and discomfort.

Contraction

Dogs most commonly become infected after accidentally swallowing eggs in feces or soil, or other contaminated objects in the environment.  Whipworm eggs are especially resistant in the environment, and can survive for at least five years after being deposited by an infected animal.

Symptoms

In the early stages, not all dogs will show symptoms of whipworm, so regular testing for internal parasites at your veterinarian is key, even if your dog is asymptomatic.  If your dog is showing signs of the worm, you will most likely see bloody diarrhea and severe anaemia (a deficiency of red blood cells or of hemoglobin in the blood), which could lead to death in the absence of treatment. Chronic infestation causes progressive weight loss and dehydration.  When whipworm attaches to the cecum and colon, it causes internal irritation. The more whipworms that are present, the more irritation they cause. This irritation can lead to weight loss, diarrhea, and bloody stools. These are all symptoms of other serious conditions and ailments, so if you notice any of these signs in your pet, contact your vet immediately.

Dangerous to Humans?

Humans have their own species of whipworm called Trichuris trichiura, that is only spread through human feces.  It is extremely rare for humans to get whipworm from dogs, however, you should always wear gloves and wash your hands when handling dog feces, as it may contain other dangerous parasites and diseases that are harmful to humans.

To learn about the treatment and prevention of worms, check out Dog Treatment and Prevention.

Heartworm for dogs

Heartworm is a serious disease that can cause severe heart and lung problems, and can ultimately lead to death.  Dogs, including fox, coyotes, and wolves, are the main heartworm hosts, but these parasites can also impact other mammals such as cats.

When an animal has heartworm disease, an average of 15 worms is considered a burden in dogs.  However, after about a year of infestation, a dog could potentially be harboring hundreds of worms, causing extreme damage to the heart and other parts of the body (American Kennel Club, 2018).

Appearance

Adult heartworms look like strands of cooked spaghetti.  Males can reach 4 to 6 inches, and females reach about 10 to 12 inches in length.

Contraction

heartworms in dogsIn order for a dog to become infected, there must be a mosquito that bites the animal and deposits immature worms while taking a blood meal.  Infection cannot be transmitted from dog to dog. Microfilaria (immature worms) travel in the bloodstream for about two months and then settle in the right side of the heart.  This is the side of the heart where the blood enters from the body, and is then pumped into the lungs for more oxygen.  After six months of growth, the worms live in the dog’s body for up to seven years until they are about a foot long and begin reproducing (Center for Veterinary Medicine).

Symptoms

In the early stages of heartworm, a dog will not exhibit any signs or symptoms.  About 6 months after the initial mosquito bite, a blood test will show antigens or microfilaria, according to the American Heartworm Society.  There are four classes (stages) of heartworm disease, and the higher the class, the worse the symptoms and the disease are in dogs.

  • Class 1: No symptoms, perhaps a mild cough.
  • Class 2: Some mild struggle with exercise, and a continuing cough.
  • Class 3: More exercise intolerance, weak pulse, fainting, and heavy breathing sounds.  There may be a weakened appetite, weight loss, and a swollen stomach.
  • Class 4: Caval syndrome, an illness characterized by anorexia, respiratory distress, and anemia as some of the major symptoms.  The blood has a hard time flowing back to the heart because it is blocked by the large mass of worms.

Dangerous to Humans?

Humans are not a natural host for Heartworm, as it is a specific parasite that typically only affects dogs, cats, and some other mammals.  In rare cases, heartworm can infect humans but they do not complete the life cycle in the human body.

To learn about the treatment and prevention of worms, check out Dog Treatment and Prevention.

Lungworm for dogs

Lungworm is a parasitic worm that typically affects dogs and foxes.  After infection, lungworms live in the heart and major blood vessels of the lungs.  They cause respiratory illness, including coughing and lethargy during exercise. Additionally, they can also eventually lead to hemorrhaging in the lungs, liver, intestines, spinal cord, and eyes.  Infestation can cause blood clotting issues, resulting in excessive bleeding from small wounds, nose bleeds, and bleeding into the eyes.  The inability to clot is also an issue if a dog were to need surgery, such as neutering or any other major surgery.  In more than 10% of cases, lungworm leads to death (Blue Cross).

Appearance

Adult lungworms are long and thin with males ranging from 1.5 – 2.5 cm long and females from 2 to 4 cm long.

Contraction

Unlike other worms, a dog can only contract lungworm if he or she eats larvae in a slime trail that is found in infected snails, slugs, and frogs, or by eating the snail, slug, or frog itself.  The worm needs one of these hosts in order to grow and mature.

Symptoms

Lungworm is a chronic disease that can last months to years, but may occasionally cause sudden death.  Common symptoms are often similar to other diseases, including coughing and lethargy during and after exercise.  Infestation may also lead to blood clotting issues, weight loss, breathing difficulties, lack of appetite, vomiting, and diarrhea to name a few (The Kennel Club).

Dangerous to Humans?

Lungworm has not been known to infect humans, but you should always wear gloves and wash your hands thoroughly after dealing with feces to protect yourself from other disease that may be transmitted from dog feces.

To learn about the treatment and prevention of worms, check out Dog Treatment and Prevention.

Tapeworm for dogs

Unlike other intestinal worms, tapeworms cannot be transmitted through ingestion or eating fertilized eggs.  The parasite must first pass through an intermediate host, such as a flea in order to infect a dog. Individual segments of the worm start to develop behind it’s head, and move down the length of the worm as they mature before they are ultimately shed and passed in the dog’s stool.  After being passed, each segment begins to dry and turns a light, golden color that breaks open and frees fertilized eggs into the environment (American Kennel Club, 2015).

Appearance

Tapeworms are flat, segmented worms, and each segment is about the size of a grain of rice.  Adult tapeworms usually measure anywhere from 4 to 28 inches in length.

Contraction

tapeworms in dogsA dog will first ingest a host that has tapeworm eggs inside of it, typically an adult flea, which may occur during grooming.  Other potential animal hosts include birds or small rodents. After the dog has ingested the eggs, they will settle into the small intestines where they will then develop into adults.  As the tapeworm matures, the segments of its body begin to break off and will leave the body in the dog’s feces (VCA).

Symptoms

There are a few tell-tale signs of tapeworms in dogs.  According to the Centers for Disease Control and Prevention, the segments of the worm can occasionally be seen crawling near the anus of the dog or on the surface of waste that was just deposited.  The segments can also sometimes get stuck to your dog’s fur around their rear-end, making them visible to see. Additionally, the worms can be irritating to a dog’s bottom, causing him or her to scoot his or her backside across the floor.  Tapeworms are not typically harmful to dogs, but weight loss and lethargy may occur if your dog has a large infestation, even when eating normally.

Dangerous to Humans?

Tapeworms can be passed to humans, but the risk of infestation is low.  Children are most prone to contracting a tapeworm since they play in grass and parks where dog stool may be left.

To learn about the treatment and prevention of worms, check out Dog Treatment and Prevention.

Stronglyoidiasis for dogs

There are several types of strongyloides worm, including Strongyloides stercoralis and Strongyloides canis.  Strongyloides stercoralis is commonly known as threadworm or pinworm, and is the primary species found in dogs and humans.  Strongyloides canis also affects dogs, and other species of the worm can be found in cats and farm animals.

Appearance

The parasitic form of these worms are all female and about 0.2 cm in length during the adult stage.

Symptoms

Common symptoms include watery diarrhea or diarrhea with blood and mucus, weight loss, lack of appetite, and intestinal inflammation.  Other symptoms include reduced growth or pneumonia in puppies, fever, and shallow, rapid breathing.

Contraction

These worms thrive in hot, humid climates, and are spread through poor hygiene, contact with infected feces, or ingestion of feces.  Puppies are also at a high risk of contracting these worms as they can become infected though their mother’s milk while nursing (transmammary infection).

Dangerous to Humans?

Cross contamination from dog to human is possible, and the primary species found in humans and dogs is Strongyloides stercoralis.  In order to prevent contracting these worms, it is important to practice good hygiene and frequently wash your hands.

TOP 5 FAQ

What causes roundworms in dogs?

Roundworm eggs can be transported by small animals including rodents and birds, and when a dog eats one of these infected animals, the egg can be transported to the pup and grow into a roundworm in the dog’s intestines.

Can lungworms kill my dog?

Lungworm is a chronic disease that can last months to years, and may occasionally cause sudden death.  If you think your dog has contracted lungworm, contact your veterinarian immediately.

OTHER FREQUENTLY ASKED QUESTIONS