Heartworm in Cavalier King Charles Spaniels

What is heartworm?

Heartworm is a parasitic infection caused by Dirofilaria immitis. Adult heartworms live primarily in the pulmonary arteries, the blood vessels that carry blood from the heart to the lungs. As the infection develops, the worms can cause damage to the pulmonary blood vessels and place increasing strain on the cardiovascular system.

Heartworm disease can become severe and potentially life-threatening if it is not prevented or treated.

How does a Cavalier get heartworm?

Heartworm is transmitted by mosquitoes. The life cycle begins when a mosquito bites an infected animal and picks up microscopic heartworm larvae called microfilariae. The larvae develop inside the mosquito before being transmitted to another dog when the mosquito feeds again.

This means a Cavalier does not need to have direct contact with another infected dog to become infected.

A mosquito can transmit heartworm simply by biting an infected animal and subsequently biting another dog.

Can my Cavalier get heartworm in Australia?

Yes. Heartworm is present in Australia, and the risk varies according to geographical location and environmental conditions. Mosquitoes are the essential vector for heartworm transmission, so areas with suitable mosquito populations can present a risk.

Your veterinarian can advise you about the level of heartworm risk in your area and recommend an appropriate prevention program for your Cavalier.

Why is heartworm dangerous?

Heartworm disease can cause significant damage to the lungs and cardiovascular system. As adult worms accumulate, they can damage the pulmonary arteries and contribute to increased pressure within these blood vessels. In more advanced disease, the heart can become affected and heart failure can occur.

Severe heartworm disease can cause:

• Exercise intolerance

• Persistent coughing

• Difficulty breathing

• Weight loss

• Weakness

• Abdominal swelling

• Abnormal heart rhythms

• Collapse

In severe cases, a condition known as caval syndrome can occur. This is a life-threatening complication associated with a large number of adult worms interfering with blood flow through the heart.

Signs of heartworm disease in Cavaliers

Heartworm disease can be difficult to recognise in its early stages because a dog may show few or no obvious signs initially.

As the disease progresses, signs can include:

• Persistent coughing

• Reduced exercise tolerance

• Reluctance to exercise

• Tiring easily

• Difficulty breathing

• Weight loss

• Weakness

• Abdominal swelling

• Collapse

The severity of signs depends on factors including the number of worms present and the degree of damage caused by the infection.

If your Cavalier develops unexplained coughing, breathing difficulties, weakness or reduced exercise tolerance, contact your veterinarian.

Can heartworm be prevented?

Yes. Heartworm is considered a preventable disease, and prevention is much easier than treating an established infection.

Veterinary parasite-control guidelines recommend year-round heartworm prevention for dogs. Preventive products are available in different formulations, including oral, topical and injectable products.

Your veterinarian can recommend the most appropriate product and schedule for your Cavalier based on their age, weight, health, lifestyle and local parasite risks.

Why is regular heartworm prevention important?

Heartworm prevention needs to be given consistently according to the schedule recommended by your veterinarian. Missing doses can leave your Cavalier unprotected against infection. Because heartworm develops over time, a dog may appear completely healthy while an infection is developing. Consistent prevention helps stop immature heartworm larvae from developing into adult worms.

Do indoor Cavaliers need heartworm prevention?

Even Cavaliers that spend most of their time indoors can be exposed to mosquitoes. A mosquito can enter a home and bite a dog, meaning an indoor lifestyle does not completely eliminate the risk of heartworm infection.

Your veterinarian can help you determine the appropriate heartworm prevention program based on your Cavalier's individual circumstances.

Can heartworm spread directly from dog to dog?

No. Heartworm is not spread through ordinary contact between dogs.

An infected mosquito is required to transmit the parasite from one animal to another. Your Cavalier therefore cannot become infected simply by playing with, grooming or sharing a home with another dog that has heartworm.

Does heartworm prevention kill adult heartworms?

Heartworm preventives are primarily designed to prevent immature stages of the parasite from developing into adult worms. They are not simply a treatment for established adult heartworm disease.

If a dog is diagnosed with heartworm, treatment needs to be carefully managed by a veterinarian. Established heartworm infection can cause significant cardiovascular and pulmonary disease, and treatment itself needs to be approached carefully.

Never attempt to treat suspected heartworm infection yourself.

Should my Cavalier be tested for heartworm?

Your veterinarian can advise you about appropriate heartworm testing for your Cavalier. Heartworm testing commonly involves blood testing for evidence of infection. Antigen tests can detect proteins associated with adult female heartworms, while other tests can be used to detect microfilariae.

Veterinary guidelines recommend regular heartworm testing, including for dogs receiving prevention, because no preventive program provides an absolute guarantee against infection.

Your veterinarian will determine the most appropriate testing schedule for your Cavalier.

What happens if a Cavalier tests positive?

If your Cavalier tests positive for heartworm, your veterinarian will assess their overall health and determine the appropriate treatment plan.

Additional diagnostic tests may be required to establish the extent of the infection and assess the heart and lungs.

Treatment aims to eliminate adult heartworms and, where appropriate, microfilariae while managing the effects of the disease.

Treatment should always be undertaken under veterinary supervision.

Heartworm and Cavalier King Charles Spaniels

Cavalier King Charles Spaniels are particularly loved for their affectionate nature and companionship, but responsible ownership includes protecting them from preventable diseases.

Heartworm prevention should be considered alongside other important aspects of Cavalier healthcare, including regular veterinary examinations, vaccination, dental care, parasite control and monitoring for breed-associated health conditions.

Keeping your Cavalier's parasite prevention up to date is a simple but important part of their overall health care.

Don't wait until you see symptoms

One of the biggest problems with heartworm disease is that obvious symptoms may not appear until significant damage has already occurred. A Cavalier can look perfectly healthy while an infection is developing.

This is why prevention is so important. Rather than waiting for signs of disease, speak with your veterinarian about a consistent heartworm prevention program appropriate for your Cavalier.

A simple heartworm prevention routine

Protecting your Cavalier can be straightforward:

1. Speak with your veterinarian about heartworm prevention.

2. Use the recommended product exactly as directed.

3. Give or apply it according to the recommended schedule.

4. Keep track of treatment dates so doses are not missed.

5. Attend regular veterinary health checks.

6. Ask your veterinarian whether heartworm testing is appropriate.

7. Seek veterinary advice if your Cavalier develops unexplained coughing, breathing difficulties, weakness or reduced exercise tolerance.

Consistency is one of the most important parts of effective parasite prevention.

Heartworm prevention is part of responsible Cavalier ownership

Heartworm is a serious disease, but it is also largely preventable. A consistent, veterinarian-recommended prevention program can help protect your Cavalier King Charles Spaniel from this potentially life-threatening parasite.

Don't wait until your Cavalier becomes unwell. Talk to your veterinarian about the heartworm risks in your area and the most appropriate prevention program for your dog.

A few minutes spent keeping parasite prevention up to date can help protect your Cavalier's heart, lungs and long-term wellbeing.

Disclaimer

The information provided in the Cavalier Knowledge Centre is intended for general educational purposes only and is not a substitute for veterinary advice, diagnosis or treatment.