The arrival of mosquitoes is an annoying, and potentially dangerous, reality of spring. These tiny pests can pose a serious risk to pets – heartworm disease. Once thought of as a southern state problem, heartworm is now prevalent in all 50 states and Canada, making protection critical for all pets.

What is Heartworm Disease?

Heartworm is a type of roundworm, Dirofilaria immitis, which lives in the heart and pulmonary arteries of dogs, cats, and wildlife (coyotes are a main carrier). Transmitted by over 30 types of mosquito, it causes permanent and severe damage to the heart and internal organs.

How Does My Pet Get Heartworm?

The heartworm life cycle is long and complicated. The basic steps to infection are:

  • An infected animal is bitten by a mosquito, which takes up the heartworm larvae (microfilariae) into its body.
  • The same mosquito bites another pet, injecting the microfilariae into that pet’s body.
  • In the new pet’s bloodstream, the baby heartworms circulate and develop further.
  • The microfilariae reach the pet’s heart and lungs where they mature into adult heartworms.
  • After about 6-7 months of infection, the adult heartworms reproduce and send new baby microfilariae into the pet’s bloodstream. The pet is now a carrier and can spread the disease with the next mosquito bite.

Symptoms and Signs of Heartworm Disease

Heartworm disease signs may be subtle at first, and are similar to the signs of many other diseases. The signs are also different between dogs and cats.

Signs of heartworm in dogs:

  • Exercise intolerance
  • Lethargy
  • Bulging chest
  • Soft, dry cough
  • Rapid breathing
  • Weight loss
  • Collapse

Signs of heartworm in cats:

  • Wheezing
  • Sudden onset cough
  • Vomiting
  • Rapid breathing
  • Weight loss
  • Sudden death

Treatment of Heartworm Disease

Treatment of heartworm disease is costly, time consuming, and risky.

In dogs, treatment consists of a series of injections that kill the adult worms over several weeks. The dead and dying worms pose a great risk to the dog, since they can block pulmonary blood flow and oxygen flow to the heart. This could cause respiratory distress and even death in some cases. Because of these risks, dogs should be monitored in the hospital after each injection. They must also be on exercise restriction during the entire course of treatment in order to mitigate these risks.

Sadly, the same drug is not approved for use in cats. Cats can have a strong reaction in their lungs as the heartworms respond to the medication and die, which can have fatal results. Some choose to treat the cat anyway and hope there is no reaction.  Others choose to treat the symptoms of heartworm in cats, and heartworm associated respiratory disease (HARD) and hope that the cat outlives the worms. Worm lifespan in cats is 2-3 years compared to 5-7 years in dogs. Either way, the worms continue to damage the heart and lungs during this time, and an acute respiratory emergency is possible at any time.

Heartworm Prevention

Fortunately, heartworm prevention is safe, effective, and affordable when compared to treatment of the disease or it’s symptoms. We can prescribe a monthly oral tablet or a topical to apply. Heartworm preventives should be given year-round in order to assure that any heartworms that make it into your pet’s bloodstream never get the chance to reach adulthood.

At Old Derby Animal Hospital, our main goal is to keep your pet healthy and happy for life. By working together, we can keep them free from heartworm. Give us a call or schedule an appointment and use springtime as the right time to get back on a preventive care routine that protects your pet all year.