How to Identify Different Dog Worms

Three Parts:Identifying a Worm InfectionDistinguishing Types of WormsPreventing or Treating Worms

There are many different types of worms that can infect dogs. Those of most concern are roundworms, tapeworms, heartworms, hook and whipworms. Whilst each type of worm has a slightly different life cycle, the dog’s symptoms can be consistent with different types of worm infections. Thus, it is not possible to determine what sort of worm your dog has based on symptoms alone, and tests may be necessary.[1] However, knowing the general symptoms, risks, and characteristics of different types of worms can help you treat and care for your canine friend.

Part 1
Identifying a Worm Infection

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    Be aware of risk factors for specific types of worms. Because worms can look very similar, one of the best ways to identify the type of parasite that is plaguing your dog is to understand the environmental or situational factors that most lead to each type of worms. [2]
    • Roundworms are often passed to puppies from a roundworm-infested mother because the eggs and larvae cross the placenta to infect the puppy in the womb, and eggs are also excreted in the mother's milk. Puppies should be wormed as a matter of routine.
    • Tapeworms are caused by a dog’s eating vermin already infected with tapeworm, or from fleas that contain tapeworm eggs. Thus, hunting dogs or dogs with a flea infestation are likely to pick up tapeworms.
    • Hookworms and Whipworms thrive in damp soil and the dogs most at risk are those kept on grass runs, especially in warm, humid conditions. These infections are more common in kenneled dogs that have access to communal grassy runs.
    • Heartworm is spread by insects such as mosquitoes and is therefore endemic in certain areas where insects are more common. High risk areas include the Southeastern and Midwestern United States and along the Atlantic coast.
    • Lungworm is becoming more prevalent and is spread via fox feces, slugs, and snails. Contact with any of these is considered a risk factor.
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    Watch for symptoms. Many of the symptoms of worm infections are general and non-specific. Thus, it is not possible to diagnose what sort of worms a dog may have, based on symptoms alone. However, signs in a dog that has not been wormed recently should raise suspicion of worm infection and trigger an investigation into what sort of parasite is present.
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    Look for worms in feces. Sometimes, even in an asymptomatic dog, you may see physical evidence of the worms in the dog’s feces. If you are not completely confident in worm recognition, collect the worm in a screw-top container and take it to the vet clinic for identification.
    • Collecting a worm is far more helpful to your vet than describing it, since most worms have similar physical appearances to the naked eye.
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    Identify gastrointestinal signs. Although life-cycles vary, all worms will at some point travel through the gut. If the numbers are low, then the dog may not show any signs. However, when larger numbers colonize the bowel they can cause irritation to the lining which results in symptoms such as sickness, diarrhea (sometimes with mucus and/or blood), poor appetite and weight loss. [3]
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    Collect a fecal sample. Worms either live in or transit through the gut, thus at certain stages in their life cycle evidence of infection is passed out in the dog's feces. In a heavy infestation you may see actual worms in the feces, but this is less common if mild infections. Instead, either eggs or larvae may be present in the feces, which is harder for the naked eye to spot. [4]
    • Scoop a sample of feces with a popsicle stick or a disposable spoon and place it in a clean, screw-top container that has a tight-fitting lid (your vet can provide you with a container specific for this purpose if you don’t have anything appropriate).
    • Store the sample below 30 degrees Celsius and drop it off at the vet clinic when you can (the sample does not have to be especially fresh to have evidence of worms.
    • If your vet asks for a pooled sample, you will take samples from the dog’s stool once daily for 3 days in a row, placing them in the same collection container. This may be necessary for a suspected "false negative" result. The pooled sample reduces the risk of unreliable results.
    • The vet may run the fecal analysis, which involves examining a smear of feces under the microscope to look for worm eggs or larvae, or she may send it to an outside lab for assessment.
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    Ask your dog’s vet for a blood test. Some worms that cause serious illness, such as lungworm or heartworm, can be diagnosed on a blood test. The veterinarian draws a small volume (1-2ml) from the pet to obtain as the test sample. [5]
    • A variety of tests are available but in practice an ELISA test is most common. The test looks for the presence of antibodies to the heartworm and causes a color change if positive.
    • Most veterinarians in high-risk areas for heartworm require a yearly test as part of the dog’s physical checkup before renewing or prescribing a monthly preventative treatment.
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    Avoid contact with feces and worms. Some worms, such as roundworms, can be transferred from dogs to humans. Young children who become infected with roundworms may experience damage to their eyesight.
    • Worms or feces infected with worms should be removed from children’s play areas.
    • Infected feces should be handled or collected with gloves.
    • Always wash your hands thoroughly with soap and water after handling animal feces.

Part 2
Distinguishing Types of Worms

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    Document your dog's symptoms or risk factors. Sometimes the best way to diagnose the types of worm is to document the risk factors for the dog. Make notes of the dog’s environment, climate, and habits. Be sure to also document the severity and duration of any symptoms of illness and provide the information to your veterinarian if you suspect an infection.
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    Look for distinctive features of worm types. If worms or worm parts are visible in the dog’s feces or vomit, you may be able to identify the type of worms. While many worms look similar, each has some distinguishing characteristics that may allow you to pinpoint the worm variety. [6]
    • Roundworms look a lot like cooked spaghetti noodles. They average 8 - 10cm long, but can reach 18cm in length. They have a round profile and smooth bodies.
    • Tapeworms are distinctive with flattened bodies made up of segments. The length varies with the species but averages from 50 centimeter (19.7 in) to 250cm long. If you see tapeworms in the feces or vomit, it is likely to be individual segments, not the entire tapeworm.
    • Hookworms and Whipworms are much smaller than roundworms or tapeworms. They are usually between 0.5- 2 cm long and extremely thin, like a strand of thread or hair. Their small size tends to make them appear translucent, and they can be more difficult to see without close examination.
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    Watch for respiratory or cardiac signs. Lungworm and heartworms infest blood vessels and either the heart or lungs. This can cause symptoms such as coughing, heavy or rapid breathing, lack of energy, or even collapse and death. [7]
    • Lungworm and heartworm can interfere with blood clotting and so some dogs show the alarming symptom of uncontrolled bleeding after a minor injury.
    • Any of these signs should prompt an immediate visit to your vet. Though treatments can be costly, prompt treatment is more likely to result in a favorable outcome.
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    Check for egg packets. A sure sign of tapeworms is egg packets stuck to the dog’s fur near his anus. This happens when the mature tapeworms release eggs into the bowel lumen, after which the eggs wriggle out of the dog's anus, which can also cause itchiness around the anal ring. [8]
    • These egg packets look like sesame seeds or small rice grains stuck to the hair near the dog's bottom.
    • If you look carefully you can sometimes see these small, cream-colored seed-like objects wriggling.
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    Check the dog’s physique. Because worms, particularly tapeworms, absorb nutrients from the dog’s food and make less available for the host, worm-infested dogs may have poor fat cover over their bones but swollen bellies due to the excessive worms in their gut. The classic appearance of a wormy puppy is a bony, ribby dog with a potbelly and a dull coat.
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    Take a worm or egg sample to your dog’s veterinarian. The best way to diagnose the specific type of worm is to let the professionals do it. They will be able to examine the worms or eggs under a microscope and have experience identifying minute differences between worm types. [9]
    • With worm eggs the differences can be subtle, such as the shape being oval instead of round, of having a plug at one or both ends.

Part 3
Preventing or Treating Worms

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    Identify and treat worms promptly. Worm infections tend to get worse the longer they are left untreated. An infection with a great number of adult worms, known as a “heavy” infection, can have adverse effects on a dog’s overall well-being, so identifying worms before the infection becomes “heavy” is the best approach.
    • Some canine worm infections can cause gastrointestinal illnesses such as diarrhea.
    • Some worm infections can ultimately lead to a dog’s death, particularly with heart or lung worms.
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    Administer a monthly heartworm preventative. Particularly if you live in a high-risk area with many mosquitoes, you should give your dog a monthly heartworm preventative. Heartworm preventatives require a prescription.
    • Most vets require a negative heartworm test to write a heartworm preventative prescription.
    • Many heartworm preventatives are meat-flavored and chewable, making them easier to administer.
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    Keep your dog free of fleas. Because some worms are transferred by fleas, keeping your dog free of fleas with a regular flea treatment can help him stay free of worms as well.
    • Some companies make a combination heartworm and flea treatment in one chewable pill.
    • It is also possible to administer a monthly topical flea treatment. This is usually squeezed onto the dog’s scruff, at the back of his neck.
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    Restrict your dog’s access to harmful environments. Ensuring that your dog stays away from environments that are most conducive to worms can help eliminate the need for de-worming.
    • Keep your dog away from warm, grassy areas shared with other dogs who have not been de-wormed.
    • Do not let your dog come into contact with wild or prey animals.
    • Avoid warm, humid climates that have high populations of bugs such as fleas or mosquitoes.
    • Do not let your dog eat or rub themselves in the feces of other dogs or wild animals.
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    Administer a de-wormer if necessary. If your dog has worms, you may need to administer a de-wormer. A precise worming protocol depends on the individual pet's risk factors, and is best discussed with your veterinarian. [10]
    • Most de-wormer is a powdery substance that can be mixed into the dog’s food or another vehicle such as plain yogurt (consult your vet before feeding your dog food made for humans).
    • Most de-wormers need to be administered only once, but if your veterinarian prescribes fenbendazole, you'll need to administer it repeatedly over the course of several days. Fenbendazole is a very gentle de-wormer frequently used for young puppies.
    • Be sure to read the directions on the package of de-wormer and consult your vet before giving your dog any kind of medication.
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    Maintain regular veterinary visits. Having your dog checked regularly by a veterinarian will keep her in generally good health. The vet will have the opportunity to identify problems before they become extreme and cause lasting harm to your canine companion.


  • Pick up your dog's feces if you're walking with him.
  • Flea control is essential at all times of the year.
  • Avoid letting your dog sniff or eat feces and other dirt. This happens a lot with puppies and is a sure way of transferring unwanted parasites.


  • If any worm infection is left untreated for too long, the infestation could eventually result in death.
  • Roundworms and hookworms can be transmitted from dog to human, so you should be careful, and know how to handle your dog's feces appropriately. Speak to your doctor if you're concerned that you or any family members may have contracted worms.
  • Heart-worms will give your dog a heart attack if not discovered and treated in a timely way.
  • If your dog shows any sign of fatigue or diarrhea and vomiting, consult a vet immediately.

Sources and Citations

  1. Prevalence of canine parasites based on fecal flotation. Iagburn, Lindsay, Vaughan et al. Comp Cont Ed Pract Vet 18, 483-509
  2. Diagnostic Parasitology. Conboy. Can. Vet J 37 (3), 181-182
  3. Veterinary Parasitology. Taylor, Coop, and Wall. Publisher: Wiley-Blackwell

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Categories: Canine Health