Worms in Dogs


Intestinal worms are creepy, gross and dangerous but, thankfully, preventable. 

It is the duty of all responsible pet owners to make sure they recognise the warning signs and promptly treat their pet for worms to reduce serious health risks. Dogs of all ages can pick up worms from contaminated soil, faeces or by ingesting infected fleas. As an owner, if you find your dog is a host for any of the five most common intestinal worms, you can reasonably suspect that they may also be carrying fleas.

How Can Dogs Catch Intestinal Worms?

Many puppies can be born with worms. Unborn pups can contract intestinal worms from their mother, either by the worms burrowing through her uterus during gestation, or by consuming her milk.

Older dogs commonly catch worms, usually Roundworms, Hookworms or Whipworms by swallowing the larvae from contaminated soil. In some cases, worms can penetrate the dog’s skin from direct contact with the infected surface. Alternatively, if your dog likes to hunt, they may be at risk of catching worms from an infected animal, like rodents or birds. Raw food too can sometime be source of infection, making dogs who like to scavenge at a high risk. Tapeworms pose a risk to all dogs as they are transmittable through fleas. In rare cases, pets may become infected with Heartworm through mosquito bites.

Symptoms for Worms in Dogs

The most common symptoms in dogs are:

  • Coughing
  • Vomiting
  • Diarrhoea
  • Lethargy
  • Pot-bellied appearance
  • Weight loss
  • Exercise intolerance
  • Visible worms on fur or in stool

Certain symptoms can be directly associated with particular worms. An infection of Heartworms or Roundworms, for instance, usually causes some kind of respiratory reaction in dogs, like coughing. 

Types of Worms in Dogs

Roundworms initially infect a dog’s intestine before tunnelling around through other bodily tissues and organs. They come in two types, Toxocara Canis and Toxascaris Leonin, and are usually picked up through contaminated soil, infected animals or via the mother. Both species are long, spaghetti like creatures that, when mature, spread through your dog’s liver and up to the windpipe. Once symptoms emerge, like coughing, the dog swallows the larvae and they get into his intestine. Once there, they grow into adult worms, lay eggs and repeat the cycle. Female roundworms can lay about 200,000 eggs a day, which leave the body through bowel movements. Special caution should be taken with the Tococara Canis Roundworm, as they are Zootonic, meaning they are transmissible to humans. Gloves should always be worn when handling contaminated soil.

Hookworms live a similar cycle to the Toxocara Canis, only they are shorter and not as common in the UK. They’re scientific term is Ancylostoma Caninum or Ancylostoma Braziliense. They burrow through the skin or paw of any dog that comes into contact with them. Once inside, it finds its way to the small intestinal mucos and, with its sharp teeth, bites down on the intestinal wall and sucks the blood from your dog. Adult Hookworms enjoy the rest of their lives here. They mate in the dog’s small intestine and, similar to the Roundworm, release their eggs back into the environment through the bile ducts.

Whipworms take up the first section of the large intestine, the Cecum. They’re also known as Trichuris Vulpris. They’re less noticeable, rarely seen in stool, not very common in the UK or Ireland and aren’t as greedy when extracting nutrients from your dog, so symptoms are comparatively less likely. Nonetheless, they are still parasites and can be ingested through contaminated soil. They are wider on one end, the head, hence the name “Whipworm”. Once ingested, they pass through the upper GI tract and hatch into larvae in the small intestine. After which, they manoeuvre to the Cecum where they develop into adults.

Tapeworms, or Dipylidium Caninum grow to many bead-like segments. Each of these segments, or sacs, are realised through the hosts bile ducts by adult Tapeworms. Each sac contains its own reproductive system, which breaks open and releases new eggs. If there are any hatching flea eggs around, the baby flea will consume the tapeworm egg, along with whatever else it can digest. As the larvae flea develops, so too does the tapeworm inside the flea. As an adult, the flea hops aboard its own host, your dog.  Once the flea is on-board your dog, its bites down into your dog’s skin and sucks its blood. Your dog, irritated by this, bites back. As your dog chews up the dead flea, the tapeworm is realised. The freed little worm finds its way to the small intestine and there he stays using six rows of teeth to stick to the intestinal wall for the rest of his adult life, depositing the sacs out though the dog’s rectum, repeating the cycle again. 

How often to Worm Dogs?

As a rule, adult dogs should be treated every three months for intestinal worms. Dogs are inquisitive creatures, they scavenge, hunt, eat and lick things that are liable to be teaming with worms, lying in wait for the right host.

Puppies in particular are at an increased risk to worms and should be treated much more frequently at every second week until they are 12 weeks old, then once a month until they are six months and finally every 3 months for the rest of their adult lives. Rural dog owners should consider worming their dogs every six to eight weeks, as their animals are more likely to scavenge and hunt, increasing their risk of Whipworms, Roundworms or Tapeworms.