Heartworm is mostly prevalent in southern France, Spain, Italy and the Mediterranean. Mosquitoes are responsible for transmitting the disease to dogs and many different species of mosquitoes can carry heartworm larvae.

Who is at risk?

British dogs could be more vulnerable as they have never encountered the disease and therefore have no resistance.

How is it spread?

The larvae of this worm (which eventually resides in the heart) are present in the bloodstream and can be transferred to an unaffected dog via a simple mosquito bite.

The life cycle of heartworm is developed in the following stages:
• Adult heartworms reside in the right heart chamber.
• Heartworm larvae are released into the dog's blood and the mosquito ingests the larvae with the dog’s blood.
• After 10 to 30 days, the infective larvae appear in the salivary gland of the mosquito, so when the mosquito bites another dog, it transmits the infective larvae.
• The larvae then migrate around the dog's body for about four months before reaching the dog's heart. The larvae mature into adult worms over the next three months.
• The process repeats itself.

Signs and symptoms

Heartworm disease is caused by damage from the adult worms once they get into the blood vessels of a dog's lungs. The worms cause the blood vessels to swell and become scarred. As the blood vessels shrink in diameter, blood flow becomes restricted and blood pressure begins to rise. Eventually, the increasing blood pressure will lead to heart failure.

Signs may take several years to manifest and include soft cough, tiredness, weakness, loss of weight and condition. Eventually heart failure may ensue.

Prevention and control

There are products available in the UK that may be obtained from your vet prior to your trip, or from a local vet on arrival. They kill the larvae after infection. An alternative would be to use a deltamethrin collar that prevent the mosquito from taking a blood meal.

Heartworm dog & cat image