Heartworm in dogs and cats
Written by Samantha |
Hearworm, also known as the Dirofilaria Immitis, is a parasite that lives around the Mediterranean whose larvae are transmitted by stinging mosquitoes. Both dogs and cats can be infected. Cats seem to be less susceptible to infection than dogs. In many cats, the larvae do not grow into adult worms and the cat has no symptoms. Because some cats can get sick or even die from the worm, it is very important to treat cats preventively against heartworm, just like dogs.
Where can heartworm occur?
Heartworm and the mosquito which transmits its larvae do not occur in the United Kingdom. Heartworm is found in southern and eastern Europe. Such as countries like Greece, Turkey, Czech Republic, Slovenia, Romania and Bulgaria. But also in countries like Spain, Portugal, Italy and large parts of France.
How does an animal become infected with heartworm?
When a mosquito drinks the blood of an infected animal, it also ingests the larvae of the heartworm. A mosquito then injects the larvae into the skin of a dog or cat. These larvae move to the heart. After 4-6 months, the larvae have grown into adult worms. If a male and a female are present in the body, the worms can start multiplying in the body of the infected dog or cat. The larvae can circulate in the blood for up to one and a half years and then be reabsorbed by mosquitoes. Adult worms can survive for years in the body of a dog or cat.
What are the symptoms?
Cats can remain symptomless if the larvae do not grow into adult worms. In animals where the larvae do grow, symptoms often appear when the worms have become adults or when the adult worms die. It can take several months before the first symptoms appear after an infection.
Symptoms can vary from:
- (chronic) coughing
- Listlessness
- General weakness
- Weight loss
- Rapid heartbeat
- Tightness
- Oedema and ascites
- Collapses/sudden collapse
- Sudden death
The severity of symptoms often depends on the degree of infection. More worms give more symptoms. Massive mortality can also cause sudden and severe symptoms, often resulting in acute mortality.
How is the diagnosis made?
There are various methods of making a diagnosis. These include:
- Blood tests: for antigens, antibodies and for circulating larvae
- Ultrasound examination
- X-rays of the heart and lungs
How can you treat heartworm?
It is very difficult to treat animals once the worms have reached adulthood. It can cause serious issues if all the worms die at once. The blood vessels can close off, which can result in the death of the animal.
In cats, adult worms are usually not terminated. Cats are often treated with prednisone to prevent changes in the lungs. Dogs can be treated with a combination of drugs to kill the worms and counteract the changes in the lungs. Treatment is lengthy and dogs must be kept very calm for at least 30-40 days and closely monitored by the vet. Surgical intervention may be required to remove the adult worms if large blood vessels are occluded. This is a very risky treatment and can only be performed in a specialist veterinary clinic.
What can you do to prevent a heartworm infection
The infection season is usually from April to October.
So if you want to take your pet on holiday with you during this period it is good to protect your animal against heartworm. The treatment should start 28 days after arrival at your holiday destination. You have to repeat this treatment every month until at least 28 days after you have left the infected area.
