Heartworms are dangerous and potentially lethal parasites that affect millions of pets every year. The parasite is spread by mosquitoes, and once transmitted, the heartworms grow and develop inside a pet’s heart and lungs, leading to severe health problems. The good news? Heartworm prevention is highly effective and can safeguard your pet from this deadly condition. Our Palm Valley Veterinary Center team recommends year-round heartworm preventives for all dogs and for cats, and our skilled staff can help determine the best preventive plan for your pet based on their lifestyle. Keep reading to learn more about the causes, signs, diagnosis, treatment, and prevention of heartworm disease in pets.

Heartworm transmission in pets 

Heartworm disease is caused by an infectious parasite transmitted by a mosquito bite. 

When a mosquito bites an infected animal, young heartworms called microfilariae enter the mosquito’s system. Within two weeks, the microfilariae develop into larvae inside the mosquito that can be transmitted to another animal via a bite. 

Heartworm disease progression in infected pets 

Once a mosquito infected with the parasite bites a pet, it transfers the heartworm larvae into the animal’s bloodstream. Over the next several months, the larvae migrate to the lungs and heart where they develop into adult worms and cause damage to the organs. Adult heartworms can grow 6 to 12 inches long and can live for several years. The adult heartworms damage blood vessels, reduce the heart’s pumping ability—resulting in severe lung and heart condition—and reproduce to release a new generation of infective larvae (i.e., microfilariae) into the bloodstream. If left untreated, this cycle will continue and can become fatal.

Heartworm disease in cats 

Cats are vulnerable to heartworm disease, but unlike dogs, they are not the preferred host for this parasite. Infected cats do not often have microfilariae circulating in their blood, and an infected cat cannot transfer the heartworm infection to another mosquito. It is harder to detect heartworm infections in cats than in dogs, and some cats are able to rid themselves of heartworms without showing any signs of the disease. However, others can die suddenly from heartworm-associated inflammation without ever showing signs of being sick. Currently, no treatment is available for feline heartworm disease, which makes monthly prevention and annual testing vital for cats.

Signs of heartworm disease in pets

Heartworm disease signs vary depending on the severity of the infection. In the early stages, a pet may not show any signs. However, as the heartworm larvae mature and the infection progresses, signs may include:

  • Coughing
  • Lethargy
  • Decreased appetite
  • Weight loss
  • Difficulty breathing
  • Abdominal swelling

In severe cases, heartworm disease can lead to heart failure, and a pet may collapse, have pale gums, and experience seizures. Heartworm-positive cats may be asymptomatic, experience respiratory difficulty that mirrors asthma or bronchitis, or suffer a catastrophic blockage that may result in sudden death. 

Heartworm disease diagnosis in pets 

Heartworm disease can be diagnosed through a simple blood test that detects the presence of antigens produced by adult female worms or the presence of heartworm-induced antibodies. In some cases, your veterinarian also may perform an X-ray or ultrasound to confirm the presence of heartworms in the heart and lungs or stage the disease’s severity. Annual heartworm testing is strongly recommended for all dogs and cats, indoor and outdoor, to identify early infection and minimize long-term damage.

Heartworm disease treatment for infected pets 

Treating heartworm disease can be expensive and challenging, and the earlier a pet is diagnosed and begins treatment, the better their prognosis is. Heartworm treatment—available only for dogs—involves a series of injections to kill the adult heartworms. The treatment does come with risks, as the dead and dying worms can form a life-threatening blockage. Before treatment begins, an infected pet may need to be stabilized with medications to address any symptoms of heartworm disease, such as coughing, fatigue, and difficulty breathing. All pets must have their activity restricted and carefully monitored during and after treatment to prevent further damage to their heart and lungs.

Heartworm disease prevention in pets 

Heartworm treatment may not be successful in all cases, particularly if the disease has progressed to a severe stage. Therefore, the best approach is prevention by regularly administering heartworm preventives.

If your pet isn’t currently on a heartworm prevention plan, contact Palm Valley Veterinary Center to schedule an examination and heartworm testing. Monthly heartworm preventives are the best way to protect your pet from infection, and our team is happy to make specific product recommendations based on your pet’s health status, lifestyle, and individual needs.