Heartworm Disease in Cats: Signs, Treatment and Prevention

Heartworm disease, often associated with dogs, is a serious concern for cats as well. Despite cats being less commonly affected, heartworms can still pose significant health risks. In this comprehensive guide, we’ll explore what heartworm disease in cats is, how it affects cats, the challenges of treatment, and the best ways to prevent it.

What is Heartworm Disease?

Heartworm disease is caused by a parasitic worm known as Dirofilaria immitis. These worms reside in the heart and adjacent large blood vessels of infected animals. Female heartworms can grow between 6 to 14 inches long, while males are about half that size. Though heartworm disease is more prevalent in dogs, cats are not immune. In fact, studies show that heartworm infections in cats are more common than previously thought, with indoor cats also being at risk.

How Are Heartworms Transmitted to Cats?

The heartworm life cycle involves two hosts. Here’s how the transmission process works:

Mosquitoes as Intermediate Hosts: Heartworms require mosquitoes to complete their life cycle. Over 30 species of mosquitoes can act as carriers. When a mosquito bites an infected animal (usually a dog), it ingests microfilariae—immature heartworm larvae.
Development in Mosquitoes: Inside the mosquito, the microfilariae mature over 10 to 30 days. The larvae then migrate to the mosquito’s mouthparts.
Transmission to Cats: When the mosquito bites a cat, it injects the infective larvae into the cat’s bloodstream. The larvae migrate to the right side of the heart and pulmonary arteries, where they mature into adult worms over about six to seven months.
Lifecycle Continuation: After maturing, the adult heartworms reproduce and release new microfilariae into the cat’s blood. These larvae live in the blood for around one month.

Unlike dogs, cats are resistant to heartworm infections, which means they usually have fewer worms—typically less than six. However, even one heartworm can cause significant health issues.

Symptoms of Heartworm Disease in Cats

Heartworm disease can present a range of symptoms in cats, which can vary based on the number of worms and the cat’s overall health. Common symptoms include:

Coughing: One of the most frequent signs, particularly if the worms are affecting the lungs.
Difficulty Breathing: Due to inflammation in the lungs and pulmonary arteries.
Vomiting: Gastrointestinal issues can occur as a result of the disease.
Weight Loss: Cats with heartworm disease often experience a loss of appetite and weight.
Lethargy: A general sense of fatigue and weakness.

In severe cases, heartworm disease can lead to sudden death, particularly if the cat experiences a severe reaction to the dead worms or if there is a massive pulmonary embolism.

How is Heartworm Disease Diagnosed in Cats?

Diagnosing heartworm disease in cats can be challenging because the symptoms often resemble other conditions and the number of worms is usually low. Here’s how veterinarians diagnose the disease:

History and Symptoms: Your vet will start by discussing your cat’s history and symptoms. Knowing if your cat has been exposed to mosquitoes or other animals with heartworms is crucial.
Testing: Blood tests can help detect heartworm infection, although no test is perfect. Tests often used include:
- Antigen Tests: Detects proteins from adult female heartworms.
- Antibody Tests: Detects the body’s immune response to heartworm larvae.
- Ultrasound: Can be used to visualize heartworms in the heart and lungs.
- X-rays: Help assess the damage to the lungs and heart.
Specimen Collection: Bringing a sample of the worm or a picture of the worm can aid in diagnosis.

Treatment Options for Heartworm Disease in Cats

Treating heartworm disease in cats is more complicated compared to dogs due to the risk of severe side effects from available treatments. Here are the main options:

Medications: No drugs are approved specifically for treating heartworms in cats. While melarsomine (used in dogs) has been tried, it can be highly toxic to cats and is not recommended due to the risk of severe side effects like acute pulmonary failure.
Symptomatic Treatment: Managing symptoms can help improve the cat’s quality of life. This approach may involve:
- Oxygen Therapy: To assist with breathing difficulties.
- Corticosteroids: To reduce inflammation in the lungs and pulmonary arteries.
- Diuretics: To remove excess fluid from the lungs.
Surgical Removal: In severe cases, surgical removal of heartworms might be considered. This procedure is complex and risky, with up to 40% mortality rate reported in some cases.

Preventing Heartworm Disease in Cats

Prevention is the best strategy for managing heartworm disease, as there are no ideal treatments once infection occurs. Here’s how to keep your cat safe:

Year-Round Prevention: Veterinarians recommend monthly heartworm preventatives throughout the year, especially in areas where mosquitoes are active year-round. In regions with seasonal mosquito activity, preventative treatment should be administered for at least six months of the year.
Types of Preventatives: There are several effective heartworm preventatives available for cats, including topical treatments, oral medications, and injections. These preventatives are safe and have a wide margin of safety, even for kittens as young as six weeks old.
Indoor Cats: Even indoor cats are at risk because mosquitoes can easily enter homes. Ensuring your cat is on preventative medication is crucial, regardless of their indoor or outdoor status.

Conclusion

Heartworm disease in cats is a serious and complex condition that requires careful management. Understanding how heartworms are transmitted, recognizing symptoms, and pursuing effective prevention strategies are essential for protecting your feline friend. Regular veterinary check-ups and adhering to a preventative regimen can help safeguard your cat’s health and well-being. If you suspect your cat may have heartworms or if you have any concerns about their health, consult your veterinarian promptly. Early intervention and prevention are key to ensuring a long, healthy life for your pet.

FAQs on Heartworm Disease in Cats

What is heartworm disease in cats?

Heartworm disease is caused by a parasite called Dirofilaria immitis, which is transmitted through mosquito bites. It primarily affects the heart and lungs.

How do cats get heartworm disease?

Cats become infected when they are bitten by a mosquito that carries heartworm larvae. Unlike dogs, cats are not the primary host, so the disease may be less severe.

What are the symptoms of heartworm disease in cats?

Symptoms can include coughing, difficulty breathing, vomiting, weight loss, lethargy, and, in some cases, sudden death. Some cats may show no symptoms at all.

How is heartworm disease diagnosed in cats?

Diagnosis typically involves a combination of a physical examination, blood tests to detect antibodies or antigens, and sometimes imaging techniques like X-rays or ultrasound.

Can heartworm disease in cats be treated?

Treatment options are limited and can be complicated. In some cases, veterinarians may recommend supportive care, but there is no approved treatment specifically for heartworm in cats as there is for dogs.

How can I prevent my cat from getting heartworm disease?

The best prevention is to use veterinarian-recommended heartworm preventatives. Regular veterinary check-ups and mosquito control measures can also help reduce the risk.

Is heartworm disease contagious?

No, heartworm disease is not contagious. It cannot be transmitted directly from one cat to another; it requires a mosquito as a vector.

Are certain cats more at risk for heartworm disease?

Any cat that spends time outdoors is at a higher risk, especially in areas where heartworm is prevalent. Indoor cats are at lower risk, but they can still be affected if mosquitoes enter the home.

How often should my cat be tested for heartworm?

It is generally recommended to test cats annually for heartworm, especially if they are on preventatives. Your veterinarian can provide guidance based on your cat’s risk factors.

What should I do if I suspect my cat has heartworm disease?

If you notice any symptoms or suspect heartworm disease, contact your veterinarian immediately. Early diagnosis and intervention can help manage the condition more effectively.