What is heartworm (Dirofilaria Immitis)?

Where does the Heartworm (Dirofilaria Immitis) parasite live?

Heartworm is making inroads in southern and eastern Europe, but fortunately dogs and cats are not yet infected with heartworms everywhere in Europe. Heartworms are not ingested from the environment like roundworms, for example. Heartworm is transmitted only by mosquitoes. The heartworm larvae (microfilaries) are transmitted to the dog or cat by these mosquitoes, when they sting. These heartworms will grow into adult worms in and around the heart and then cause physical complaints. Unfortunately, a dog only shows symptoms after about 5 to 7 months. In cats, adult worms will often not develop and therefore often do not get complaints from heartworms.

Heartworm (Dirofilaria Immitis) in dogs

The mosquitoes that can transmit heartworm larvae from infected animal to dog in Europe are usually the Culex pipiens and this is the normal stinging mosquito. When the dog is stung by an infected mosquito, it releases heartworm larvae (microfilariae) under the skin. These larvae grow into adult heartworms in the dog, this takes several months. As the name suggests, they will settle n the heart but they are mainly in the large pulmonary arteries. An adult heartworm can grow up to 30 cm long. If there is at least 1 male and 1 female heartworm between the outgrown adult worms, new heartworm larvae develop. These larvae can circulate in the blood for up to a year and a half before being sucked up by another mosquito. When heartworms grow into adult worms they can survive for up to 7 years.

Symptoms of an infection with heartworms

The problem with heartworm infection is that the dog does not show symptoms until very late. By then, the pulmonary arteries and parts of the heart are often already fairly full of adult worms. When the dog does start showing symptoms, in the beginning these are often also fairly general symptoms such as coughing, fatigue, weight loss and some shortness of breath. It is only when the adult worms have been in the lungs and heart for a longer time that they cause nasty and dangerous symptoms that can even lead to heart failure or serious lung problems. The symptoms are then more severe and may manifest as swelling of paws, head and abdomen due to occlusion of blood vessels or formation of oedema. In addition, with many adult heartworms, dogs often show more severe shortness of breath or heart problems and may even die spontaneously from this.

How do you determine that a dog is infected with heartworms?

This can currently be done in several ways but the most commonly used is currently the blood test. This examines whether there are circulating baby worms (microfilariae) in the blood or looks for antigens from the adult female worms. In addition, X-ray and ultrasound are often used to visualise worms in the pulmonary veins and heart.

What does treatment look like?

Treatment of heartworm is insidious. If you kill all the worms at once, there is a chance that the dead worms will cause blockages in the veins. A life-threatening situation. Treating the dog should therefore be done in stages and always under the guidance of a vet. With heartworm, the true rule is: prevention is better than cure!

Can you prevent heartworm in your dog?

Mosquitoes particularly live between April and October in Europe. If you take your dog on holiday to such a high-risk country during these months, it is seriously advisable to actively protect your dog against heartworm infections. Stinging mosquitoes can be repelled with remedies such as a Sersto or Scalibor, but also with spot-on remedies such as Advantix or Pulvex. Since you cannot tell from the dog whether a mosquito has indeed stung, it is additionally recommended to deworm the dog every 30 days to prevent the worms from maturing. Against the larval stages, anthelmintics like Milpro, Milbemax and Milbactor work very well. Deworm every 30 days during the stay and for at least a month after the last day of returning home.

Have you visited a high-risk country before with your dog without this treatment? Then have your dog tested for heartworm before starting this preventive measure, otherwise the worms already present will also be killed and with a large number, this should be done in doses.

-This is an automated translation-