Can Feline Species Contract Heartworms?

Can Feline Species Contract Heartworms?

Heartworm Prevention for Pet Owners: Understanding Heartworms in Cats

Heartworm prevention is essential for pet parents across North America, with heartworms diagnosed in all 50 U.S. states and southern regions of Canada. These parasites can be found in countries worldwide, except Antarctica, affecting not just dogs but various species, including cats.

As heartworms can pose a severe threat to feline health, it is crucial to understand what these parasites are, how they affect cats, and how to protect them. Monthly preventative treatments, such as Revolution Plus, can help safeguard your cat from heartworm disease.

Can Cats Get Heartworm?

The answer is yes. While heartworm disease in cats differs from that in dogs, it is vital to realize the risks and symptoms associated with this parasitic infection in cats.

Heartworms, or Dirofilaria immitis, are parasites spread to cats and dogs through mosquito bites. These parasites affect the heart and lungs due to their worm-like nature. Adult heartworms, resembling thin, cooked spaghetti noodles, typically reside in the pulmonary artery and right ventricle of the heart in cats.

Although heartworms do not usually cause direct pain, secondary conditions stemming from their presence can lead to severe distress and, in some cases, death. Cats are considered atypical hosts for heartworms, and while they may have fewer worms than dogs (typically one to three), heartworms can cause more severe respiratory disease or sudden death in cats than in dogs.

Heartworm Prevalence in Cats

A 2020 study in Florida revealed a 4% prevalence of adult heartworms in shelter cats compared to 28% in shelter dogs. The overall prevalence of heartworm disease in cats is suspected to be between 5% and 15% of the prevalence in dogs in any given area.

Causes of Heartworm in Cats

Cats acquire heartworms through mosquito bites. Mosquitoes are the only known vector of heartworms. When a mosquito bites a cat, heartworm larvae picked up from another animal (typically a dog) can enter the cat. Although most heartworms passed to a cat will not reach adulthood, those that survive will migrate into the heart and pulmonary artery, maturing into adult worms over six to eight months.

Understanding the Lifecycle of Heartworms

Adult male and female heartworms in dogs mate, producing microfilariae (baby heartworms). These microfilariae circulate in the bloodstream and are ingested by mosquitoes when they bite the dog. Within a few weeks, the microfilariae develop into stage three larvae within the mosquito, ready to be passed on to cats or other dogs when the mosquito feeds.

Once the larvae pass into the cat, they develop into immature worms in the animal's subcutaneous tissue, fat, or muscle. With the entry of these immature adult heartworms into the bloodstream, they make their way to the heart and pulmonary artery, potentially causing symptoms of heartworm disease in cats.

Human Heartworm Infection and Risk

Though humans can contract heartworms, it is relatively uncommon. Infections in humans are usually carried by mosquitoes from dogs or wild canids. A heartworm-positive cat poses minimal risk of transmitting heartworms to humans, as humans are accidental hosts and unsuitable for the worms to thrive in. In the U.S., 116 cases of heartworms affecting humans have been reported.

Heartworm Symptoms in Cats

Early detection of heartworms in cats is challenging due to the absence of symptoms that would suggest their presence. Unlike parasites that affect the stomach and intestines, heartworms are not typically found in a cat's feces. Routine veterinary examinations are essential to detect heartworms in cats before their symptoms become severe.

Common clinical signs of heartworms in cats include intermittent vomiting, diarrhea, rapid and labored breathing, coughing or gagging, loss of appetite, lethargy, and weight loss. These symptoms, particularly the respiratory symptoms, are often mistaken for feline asthma, emphasizing the importance of regular veterinary check-ups.

Stages of Heartworm Disease in Cats

The American Heartworm Society divides feline heartworm infection into two stages:

1. Stage 1: This stage occurs when the immature worms arrive in the pulmonary arteries, at which point many of them die. Cats can develop heartworm-associated respiratory disease (HARD) at this stage, with some cats dying or being euthanized due to the severity of their illness.
2. Stage 2: This stage occurs when adult worms die, resulting in an extreme inflammatory, anaphylactic response that is often fatal. Dying adult heartworms can form a clot (embolism). Cats who survive this stage often have permanent lung damage and long-term respiratory disease.

Diagnosing Heartworm in Cats

Diagnosing heartworms in cats can be tricky. After conducting a physical exam and collecting your pet's history, additional testing your veterinarian may perform to determine if your cat has heartworms includes:

• Heartworm antigen test: This test specifically detects an antigen associated with adult female heartworms, but it may yield false negatives in cats due to their smaller worm burdens and shorter lifespans.
• Heartworm antibody test: This test detects exposure to heartworm larvae and can be positive as early as two months after initial infection. However, antibodies can persist for years, so a cat who has cleared the infection on their own may still test positive.
• Chest X-rays: X-rays of the chest may reveal changes to the heart and lungs that are suggestive of heartworms.
• Echocardiogram: An echocardiogram may be beneficial in some cases to visualize worms within the right ventricle or pulmonary artery.

Treatment and Prevention of Heartworms in Cats

There is no approved medical treatment for heartworms in cats. Instead, treatments focus on managing symptoms, as the sudden death of the worms can contribute to the cat's sudden death. Emergency treatment may be necessary for cats experiencing respiratory distress or shock, with treatments including steroids, intravenous fluids, bronchodilators, and oxygen administration.

Long-term management of symptomatic cats may involve slowly tapering doses of steroids, such as prednisone, bronchodilators, and doxycycline to kill bacteria living within the heartworms and weaken them. Stress reduction in the cat's environment may also help manage symptoms.

Prevention is key in preventing heartworm disease in cats. Keeping cats indoors is one way to reduce exposure to mosquitoes, although indoor cats are not entirely risk-free. Many preventatives available for cats include monthly oral medications or topical solutions applied to the skin between the shoulder blades once a month, while a long-term injectable heartworm preventative is currently only used in dogs.

Related Conditions

• Heartworm-associated respiratory disease (HARD)
• Acute death syndrome
• Feline asthma

Heartworm disease is a reality for both cats and dogs, but understanding their differences, as well as the risks and symptoms of the disease, can help pet parents take proactive measures to protect their cats. Regular veterinary check-ups, along with strict adherence to a preventative treatment plan, will help ensure the long-term health and well-being of your feline companion.

1. In addition to dogs, heartworms affect various species, including cats, and can pose a severe threat to their health.
2. Cats can acquire heartworms through mosquito bites, which are the only known vector of heartworms.
3. Monthly preventative treatments, such as Revolution Plus, can help safeguard cats from heartworm disease.
4. Understanding the lifecycle of heartworms is vital for pet owners to protect their cats, as awareness of causes and symptoms helps in regular prevention and early detection.

Read also: