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Parasite control in puppies and dogs - intestinal worms, heartworm and fleas

Parasite Control in Puppies and Dogs

Intestinal Worms, Heartworm and Fleas

There are three main categories of parasites that are of major concern for puppy and dog health: intestinal worms, heartworm and fleas.

Intestinal Worms

These include roundworms, tapeworms, hookworms and whipworms. Many puppies are born with roundworms and can acquire hookworms from their mother's milk.

Worms can cause anaemia (loss of red blood cells), weight loss and poor condition, dull coat and in severe cases intestinal obstruction. The common tapeworm is transmitted through fleas and will often cause your dog to 'scoot'. Some of these worms can also spread to people, particularly children, and can cause problems such as blindness or large cysts that develop in body organs.

There are many intestinal wormers on the market some are more effective than others and some may not treat all types of worms. Intestinal wormers should be given to puppies every two weeks until 12 weeks of age, then monthly until six months of age, and thereafter every three months throughout your dog's life.

The intestinal wormers that we recommend are Drontal chews or Popantel tablets. The dosage depends on the pet's weight and as puppies grow quickly it is always advisable to weigh your puppy before medicating to ensure it is getting the right dose. There are also combination products that will treat intestinal worms as well as other parasites; see below for more details.


Heartworm is a special type of worm that is distinct from intestinal worms. The adult stages of the parasite live within the heart and the blood vessels of the lungs, causing serious disease and even death. Heartworm is transmitted by mosquitoes.

The mosquito injects heartworm larvae under the skin as it feeds; these migrate to the heart and lungs where they develop into adult worms over a period of six months. These adult worms then cause blood clots to develop and increase the strain on the heart, eventually causing heart failure.

An excellent heartworm preventative we recommend is Proheart SR-12, as it is an injectable heartworm preventative that provides year-long prevention of heartworm via a slow-release drug. In their first year, however, puppies need more frequent injections while they are growing. Current recommendations are to give puppies an injection at three months of age (i.e. at second vaccination) and again at six months of age. Booster injections are then continued throughout your dog's life and are often done at the same time as yearly booster vaccinations.

There are also combination medications available that will prevent heartworm, as well as other parasites. See below for details of combination preventatives.

Please note that heartworm preventatives will only prevent heartworm infection: they do not treat heartworm if your dog is already infected and it is therefore very important to continue heartworm preventative at all times to stop infection. In fact, some heartworm preventatives may cause reactions if given to infected dogs, so a blood test is often recommended for older dogs to make sure they do not have heartworm prior to starting (or recommencing) a preventative. Please speak to our vets if this applies to you.


Fleas are a major cause of skin irritation in dogs, causing them to bite and scratch themselves and often causing significant damage to the skin in the process. Some dogs may even be allergic to fleas and a single flea bite may be enough to cause severe itching. See also our advice sheet on fleas.

Fleas are usually transferred through contact with an infested area. There may only be small numbers of fleas on a dog at any one time; however, this small number is enough to produce a vast number of flea eggs, which can settle into carpets, bedding and any other sheltered areas. A single flea can lay up to 50 eggs a day and these eggs can last up to six months before hatching.

There are several flea preventatives on the market. However, be aware that flea collars, powders and shampoos will NOT be effective in controlling a flea problem, as they do not provide sustained control for a long enough period.

We recommend the topical spot-on treatments to prevent flea infestation; these are drops that are applied to the back of the neck between the shoulder blades. They should be applied monthly, or as directed, and are very effective in both killing adult fleas and controlling their life cycle. If there is a significant flea problem already in the house, a 'flea bomb' may be required to kill the eggs and larvae already present in the house. Also remember that other animals may carry fleas, in particular cats, so all animals in the household, as well as their bedding, must be treated at the same time to prevent flea problems developing. There are also combination treatments available that will treat fleas as well as other parasites; see below for more details.

Combination Treatments

There are several combination treatments on the market that will treat most, or all of the parasites mentioned above, making it easier for you to ensure good parasite control. These include:

  • Nexgard Spectra chewable tablets given monthly
  • Bravecto chewable tablets given 3 monthly
  • Advocate Spot-On applied monthly

Please speak to our team for advice on tailoring a preventative plan to best suit you and your pet's needs.

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