Worms in Dogs

By Dr Eloise Bright 7 Min Read

Whilst worms in dogs are mostly invisible, keeping your canine companion worm free is an absolute must for their health and comfort.

Even though worms aren’t obvious, it’s important that you know about what they can do to your canine best friend and how to keep them under control.


There are a number of worms that can live inside your dog’s body, and none of them are very pleasant.

  • Roundworm. Puppies can be infected with roundworm while still in the womb and also while nursing. They can cause ill thrift, vomiting and diarrhoea. In large enough numbers, they can cause an intestinal obstruction which can make your dog seriously ill. These are quite large worms and you may see them in your dog’s faeces or in his vomitus. Roundworm larvae can infect humans, and cause eye and liver damage.
  • Hookworms live in your dog’s small intestine and drink blood. They can drink enough blood to cause anaemia, and they can kill young pups. If your dog has hookworm, his gums may be pale and you can expect his faeces to be very dark and tarry, because of the digested blood in them. Hookworms also affect people, with the larvae crawling around just under the skin causing a red itchy rash.
  • Whipworm. These can be found in your dog’s caecum, equivalent to your appendix, and his large intestine. The eggs are very hardy and can survive in the ground for years, which means the soil is a constant source of infection. Whipworm cause severe inflammation of the intestine, resulting in diarrhoea containing blood and mucous.
  • Tapeworm. Dipylidium is spread by fleas and doesn’t cause any major health issues except an itchy bottom. You may see tapeworm segments, like wriggling grains of rice, around your dog’s anus or on his droppings. Echinococcus also doesn’t affect dogs much, but the eggs shed by this tapeworm can infect people and cause fluid filled cysts in organs such as the liver, lungs and brain.
  • Heartworm. These worms are spread from dog to dog by mosquitoes. Unlike the other worms, heartworms don’t live in your dog’s gastrointestinal tract but in the large blood vessels carrying blood from the right side of the heart to the lungs. They cause blood clots and inflammation in these vessels and interfere with blood flow. If it isn’t treated, the result is heart failure with coughing, fluid accumulation and ultimately, death.


There are many worming treatments available to dog owners and they are all similar in that they don’t actually stop your dog getting worms. They do however kill the worms before your dog has enough in his body to cause disease.

  • Allwormer tablets are manufactured by several companies but all are similar in that they only kill intestinal worms. There are many brands but some of the best known are Drontal and Exelpet. Puppies should be treated two weekly until they are 12 weeks old, then monthly until they are 6 months old. After this, they can be dosed every three months, just like adults.
  • Heartworm can be controlled with a monthly tablet such as Proheart or a yearly injection called Proheart SR12. If you think you may forget to treat your dog each month, then the heartworm injection may be best for you.
  • A busy lifestyle can make it hard to remember everything your dog needs. If you’re looking for something to control several of his parasites at once, then again you have a number of choices. Interceptor and Heartgard control heartworm and intestinal worms, Sentinel Spectrum and Panoramis do the same but also keep fleas in check.
  • Some dogs object to taking a tablet and it can be difficult making them swallow it without risking your fingers! There’s a convenient solution to worm control for you too. Advocate and Revolution are liquid spot-ons which are squeezed onto the skin on the back of your dog’s neck once a month. They control heartworm, intestinal worms and fleas in one easy application.


If your dog has intestinal worms, then any of the worming treatments can be used. There is no worming treatment that is 100% effective, and they also don’t kill immature worms that are developing in your dog’s body. You can worm your dog as frequently as 3-4 weekly if necessary to clear up a stubborn infection.

Heartworm is more challenging to treat. Killing the worms can cause even more inflammation in your dog’s blood vessels, and his symptoms may worsen significantly. For this reason, treating them is a two-step process. Firstly, the adults are killed with a drug called Immiticide. This is done under close veterinary supervision because the dead and dying worms can cause clots in his blood vessels. Several weeks later, the immature larvae in the bloodstream are killed, usually with ivermectin or milbemycin.


If you’re a busy person with a lot of responsibility, it can be hard to remember to worm your dog regularly. However, if your dog does become infested with worms, the effects on his health can be devastating. It’s not worth the risk. There are a number of ways you can prevent worms in your four legged family member; you’re sure to find one that fits in to your schedule.

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Dr Eloise is a Clinical Lead at Love That Pet and one of our resident pet care experts. She also curates the select range of vet recommended and approved products which feature on our site.
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