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Signs and symptoms of worm infestation

This article is intended as a guide only; always follow the advice of your veterinarian

How do you tell if your dog has worms?

Worms are one of the most common health problems for dogs but, fortunately, they are also very treatable. Therefore it is important to learn how to recognise if your dog has worms and seek veterinary advice in order to obtain the appropriate medication.  Worm infestations can be totally asymptomatic and if you suspect your dog has worms the recommended course of action is a faecal exam carried out by your vet. Common symptoms such as weight loss and poor coat quality can be indicative of a wide array of problems and you should seek veterinary advice if your dog shows these symptoms in order to obtain the correct diagnosis.

Common symptoms:

  • Visible worms or eggs in faeces - This is the most common way to confirm that your dog has worms. However, not all kinds of worms are visible to the naked eye.
  • Visible worms in fur, or area around dog's rear - Tapeworms, in particular, may appear as small moving segments, which later dry out to resemble grains of rice.
  • Scratching or rubbing of rear on the ground or against furniture - if your dog shows signs of itchiness around the rear, it may be irritated by worms in the area. However, this could also be due to problems with anal glands (completely unrelated to worms).
  • Vomiting with visible worms - if your dog has worms, you may also see them in your dog's vomit.
  • Bloated stomach or belly - This is another common symptom of worms, often seen in puppies who contract worms from their mother.
  • Weakness, increased appetite, constant hunger and weight loss - If your dog has worms, the worms are stealing your dog's nutrition. Your dog may be weak or constantly hungry, and in severe cases, may be losing weight.
  • Diarrhoea, particularly with blood in it.

When your dog is at risk

  • New born puppies - roundworm eggs can form cysts in adult dogs that remain dormant. These eggs cannot be removed by medication. When a female dog is pregnant, these dormant eggs will activate and infect the puppies. The mother's milk can also pass roundworms to puppies.
  • Contact with infected dirt - roundworm eggs and hookworm larvae can reside in dirt. If your dog comes into contact with infected dirt, he may get worms.
  • Fleas - young tapeworms can reside in fleas. If your dog swallows fleas while grooming, your dog will ingest tapeworms and be infected.
  • Hunting or eating wildlife - wild animals may carry worms, including tapeworms residing in fleas on wild animals. If your dog hunts or eats wildlife, he may swallow worms.

Symptoms and risks for worm infestation:

  • Roundworms - roundworms can grow up to half a foot in length and live in the intestines. They should be visible as small noodle-like bits in faecal matter and cause swollen bellies. Roundworms are a big problem in puppies.
  • Hookworms - hookworms are thin, small worms that "bite" or "hook" into the intestinal wall. They are not always visible to the naked eye, which means a microscope examination is needed to detect eggs in faecal matter. Hookworms can cause bleeding in the dog’s bowel because of their biting, which results in bloody stools or anaemia.
  • Tapeworms - tapeworms are flat, long worms that live in the intestines. Segments of the tapeworm that have broken off are visible to the naked eye as rice-like grains after drying out. These segments are often seen stuck to fur around the anus.
  • Heartworms - heartworms are one of the most dangerous worms because they cannot be easily detected. Heartworms are spread by mosquitoes. Heartworm can only be detected by blood testing. This disease is potentially fatal, but preventative medicine is available from your veterinarian.
  • Whipworms - whipworms are thin, thread like worms living in the large intestine. Adults may be visible to the naked eye, but faecal matter does not contain many worms, so they may be difficult to detect. A microscope examination of several faecal samples may be necessary to detect them. Whipworms are one of the most difficult worms to eliminate, but they are treatable.


For the most common types of worms, including heartworms, roundworms, hookworms, and tapeworms, there are all-in-one medications for your dog (allwormers) in flavoured chewable tablets which will kill the existing infestation. Please note that the term “allwormer” usually refers to products designed as treatment for all common intestinal worms, and may not be effective against heartworm as well.

Tablets are available to treating all four of these conditions and include three active ingredients: ivermectin (to prevent heartworm), pyrantel pamoate (to treat roundworms and hookworms), and praziquantel (to treat tapeworms). Alternatively, tablets containing milbemycin oxime and praziquantel are available to treat all four conditions.

Since this kind of medication covers all the major worm types, it is a very convenient multi-purpose medication for the average dog owner. You need to determine the correct dosage based on your dog's weight, but most of these medications require one tablet a month. Always consult your veterinarian for advice on the most suitable products and dosage for your dog’s specific requirements.