Symptoms of Worms in Dogs

Worried whether your dog has worms? This complete list of dog worm symptoms will help you decide if your pet is suffering from parasites right now.

Worm infestations can be common among untreated dogs, as worms may be transmitted in a variety of ways. For example some other parasites such as mosquitoes and fleas may pass worms to formerly uninfected animals. In addition to this, dogs coming into contact with the faeces of infected animals can also be enough to transit eggs or even juvenile worms.

Left unchecked, worm infestations can lead to discomfort and a variety of unpleasant side-effects. In extreme cases a heavy infestation of worms can even lead to death. Fortunately treating worms is normally quite simple, and vets have a variety of proven treatments on hand.

This article deals with the symptoms of worms in dogs to help you identify whether your pooch is suffering from an infestation.

However before we start there are two warnings that all dog owners should be aware of:

Warning #1: Worms Don’t Always Show Symptoms

When discussing dog worm symptoms it is important to point out that not all infected dogs show symptoms. Indeed, it is entirely possible for your dog to behave absolutely normally despite a heavy infestation.

This is important to know, as while it pays for pet owners to understand the symptoms of dogs with worms you shouldn’t rely on such symptoms to disprove the existence of worms. Instead, to be safe, it is recommended that all dogs undergo regular worming treatment as prescribed by a qualified vet. In this way you can be confident of keeping infestations to a minimum.

Warning #2: Not All Worms Are Visible To the Eye

While some tape worms or their eggs may be visible to the eye, this isn’t necessarily so for all types. Heartworms, for example, can only be seen under a microscope. Therefore don’t assume that your dog isn’t suffering from worms just because you haven’t seen any visible signs.

Keep an eye out for the symptoms listed below which can be just as useful for diagnosing problems with worms as physically observing worms.

General Symptoms of Worms in Dogs

There are some common dog worm symptoms seen in many cases. These are the most obviously and frequently-observed symptoms so it pays to start here. In addition to this there are a number of symptoms seen only in certain infestations, which are discussed below.

Diarrhoea and/or Vomiting

As many common dog worms live in the digestive tract they can cause irritation to dogs, leading to either diarrhoea or vomiting. This is even more likely to be a sign of worms if there is blood or signs of the worms themselves in the faeces or vomit.

Lethargy or Weight Loss

Tape worms feed by absorbing nutrients from your dog’s body. As a result this can also be observed either when a dog becomes tired on a regular basis, or starts to lose weight without reason. Another possible sign is a dog that doesn’t lose (or put on) weight but whose food intake increases considerably.

Scruffy Coat or Hair Loss

Another impact of worms in the body is that nutrient deficiencies can occur. The most obvious signs of nutrient deficiencies are problems with the coat or skin, such as regular scratching, irritation, hair loss or a generally dull-looking coat.

Scratching Rear End

Many species of dog worms seem to particularly affect the rear end of dogs. If you find that your dog is regularly scratching or rubbing the rear end this too can be a sign of possible worm infestation.

Visible Worms

Lastly, and most obviously, if you observe worms then there is a very high likelihood that your pet is infected. These worms may be seen actually in your pet’s fur (especially around the rear end), in their bedding or even just around the home.

Specific Worm Symptoms

Now we move onto to more specific signs of worm infestations which may be seen, depending on the exact nature of the infestation. Note that none of these are necessarily conclusive symptoms, and if you have any doubt that your pet may be infected it should be taken to a vet for a definitive answer.


Heartworms are less of a problem in the UK than in many other countries as they are generally spread by mosquitoes. If your pet is unlucky to be infected, however, the symptoms can be pretty unpleasant.

Rather than living in the digestive system like most parasitic worms of dogs, heartworms instead live in the respiratory system. As you might expect from such a parasite, the symptoms of heartworms often focus on breathing; signs can include coughing, shortness of breath and wheezing, not to mention many of the general symptoms mentioned above.


Far more common among domestic dogs are tapeworms, which infect the digestive tract. They are also very easy for a pet to contract as they are often transferred by fleas. For this reason a critical part of controlling tapeworms is ensuring that your pet remains flea-free.

Tapeworms are one of the most easily-identified worms as sections of them regularly break off and are eliminated from the body in the faeces. If you find that seem to be grains of rice in your dog’s faeces or in the coat then there is a high likelihood that your pet is suffering from a tapeworm infestation.

Another common sign of tapeworm infestations is that they cause severe irritation to the rear-end of an animal. If your dog is regularly scratching its behind or rubbing itself on the carpet then this too can be a strong indication of an infection.


Whipworms are so tiny as to be invisible to the human eye. In contrast to tapeworms, there is subsequently no chance of actually observing the worms themselves.

The most common symptoms of whipworms in dogs are blood in the faeces or significant unexplainable weight loss.


Roundworms live in the dog’s intestines and are large enough to be visible to the human eye. As a result they may be observed in faeces in some situations.

However there are two other common symptoms of roundworms in dogs which can tip you off that something is amiss. Firstly, roundworm infestations can lead to a greatly distended belly; if your dog develops a pot belly then roundworms are a likely culprit.

Secondly roundworms have been known to cause bowel obstructions, so if your pet has difficulty when defecating then this too should be a red flag that roundworms may be responsible.


Hookworms are some of the most unpleasant parasitic worms in dogs thanks to the “hooks” that they use to attach themselves to the gut lining. These little hooks mean that blood can be released from the gut. Blood in the faeces is therefore a strong indication that hookworms may be to blame.

Hookworms are also known to cause considerable skin dryness and irritation so a dog that won’t stop scratching may turn out to be infected with hookworms.

While all these symptoms of worms in dogs should be cause for concern, to re-iterate the comments earlier, it is critical that all dogs should be regularly wormed to eliminate any unpleasant infestations. Furthermore if you observe any of the signs mentioned above it is a good idea to take your dog to your veterinary surgeon for a full check-up just to be certain of the cause before resolving the issue.

Dogs can suffer from worms - but how do you know if your dog is suffering, and what can you do about infections.