Heartworms In Dogs


Heartworms in UK dogs is thankfully a problem that over 99% of UK dog owners will never have to deal with. Since the parasite is transmitted via mosquito bite and there being no mosquitos in the UK, we can rest assured – kind of.

Whilst that is reassuring for most, those of us who bring our dogs on holiday have a real concern.

Heartworms (Dirofilaria immitis) are large parasitic worms that live in the heart and the blood vessels that connect the dog’s heart to the lungs. As mentioned above: dogs get heartworms after being bitten by a mosquito that is carrying the parasite.

The infected mosquito sucks baby heartworms (microfilariae) from the blood of an already infected dog. These microfilariae then live and grow inside the mosquito. Any dogs that this mosquito bites in the future, the mosquito inadvertently injects these heartworms directly into the dog’s bloodstream.

It can take 4-6 months for a microfilaria to develop into an adult heartworm but this process can happen either within the mosquito or within the dog – or even partially in both.

Heartworms cannot be transmitted to humans nor can they be transferred from dog to dog.

As of 2020 it is widely accepted that only mosquitos can transmit heartworms to dogs and that this problem only occurs in dogs living around mosquitos or dog owners on holiday with their dog.


As mentioned above, heartworms live within the heart and surrounding blood vessels. Many dogs will not show any symptoms initially which obviously makes heartworms in dogs a difficult condition to diagnose early.

As the heartworms grow within the dog’s heart and blood vessels symptoms will soon present themselves as the parasites become too big for the dogs organs.

Symptoms of dogs infected with heartworms normally includes:

  • Coughing
  • Difficulty breathing
  • Lack of mobility
  • Bloated stomach
  • Lack of energy
  • Pale gums
  • Exhaustion

Luckily, there is a simple blood test that can be performed to confirm that any dog is infected with heartworms. Most UK veterinarians offer this service in-house and the turnaround for results tends to be pretty quick – usually within 72 hours.

Affected Breeds

No dog breed is immune to being affected by this condition. Dogs of all breeds, ages and sexes have been found to be infected by this dangerous condition.

Whilst any dog can be infected, the presence of mosquitos is required for the condition to be spread. Since mosquitos are not present in much of the World, regions where dogs live alongside mosquitos are the only ones affected.


When it comes to treating heartworms in UK dogs, killing off the larger heartworms can be a very difficult task.

There are a number of antibiotics available that will kill off much of the younger heartworms but the adults may require further treatment.

A series of injections like melarsomine are required on multiple occasions after administering antibiotics to finish off the larger worms. This can have it’s own side effects such as inflammation and irritation for the dog being treated.

Painkillers and anti inflammatory medication is also often prescribed due to the side effects mentioned above.

This treatment course coupled with isolation and relaxation for your dog will normally cure most cases of heartworms within 3-4 months.

It is important to note that this is not always successful and unfortunately some dogs never recover from heartworms and sadly do pass away because of the condition.

Treatment Cost

Treatment of heartworm in UK dogs can be a very expensive event. This cost is weighed heavier since heartworm is not native to the UK so it’s diagnosis can be difficult especially in the early days of no symptoms.

As of 2020, the average cost of treating heartworm is anywhere from £1,000-£2,500. This cost increases with any side effects or symptoms that need to be treated as a result of the heartworm.

Monthly supplies of heartworm preventative medication is available for under £40 per month.

Since only dogs travelling abroad from the UK are susceptible to the condition it is worth asking your veterinarian in advance of your holiday to avoid a large bill on your return.

Further Reading

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