Print Posted By Lost in France on 1 Sep 2008 in Living in France - Pets


Heartworm disease is a very serious and potentially fatal parasitical condition that is transmitted by mosquitoes that are infected with the heartworm larvae (Dirofilaria immitis), it can affect both cats and dogs.

Heartworms are a large type of round worm which live in the heart and large blood vessels, the parasite is prevalent in southern France and other Mediterranean countries such as Spain and Italy.

Over recent years cases of heartworm have been recorded as far north as Brittany and also along the south and south western coast of the UK, this may be due to global warming or because travelling with our pets is becoming increasingly common.

Symptoms & Signs

Symptoms of heartworm in dogs can include breathing difficulties, coughing, weight loss and weakness, cats may show the same symptoms but may also include shock, vomiting, diarrhoea and fainting.

The symptoms can take many months or even years to manifest themselves and treating the disease is both complicated and difficult so as always prevention is best. If your pet falls ill after you have returned to the UK and you suspect heartworm may be the cause then it is advisable to tell your veterinary surgeon that your pet may have been exposed to the disease.


There are many products available both in France and the UK, some are designed to kill the heartworm larvae immediately after infection and other products such as collars impregnated with deltamethrin prevent the mosquito from feeding off of your pet in the first place. Your vet will be able to advise you as to which products are the most suitable for your pet. In France some products are also available from pharmacies.


It is very important to seek veterinary advice if you suspect that your cat or dog may be suffering from heartworm as over the counter wormers may cause more harm than good in an animal with a heavy or mature infection.

Your vet can diagnose the disease with a blood test to see if the larvae are present. In animals with a heavy or mature infestation treatment can be long and difficult and often involve a hospital stay. Medication is first given to kill the adult worms but as the worms are large the animal must rest for several weeks to allow its body to absorb the dead worms, any exertion during this period runs the risk of dead worms 'breaking loose' and travelling into the lungs which is potentially fatal. In severe cases surgery may also be used to remove the adult worms from the heart.

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