Buzzing, stinging, and biting insects are often considered little more than annoying pests, but an infected mosquito’s bite can seriously affect your pet’s health. As mosquitoes buzz around you and your four-legged friend during your evening walk, keep in mind that these winged bloodsuckers often transmit heartworms. A heartworm infection can result in potentially fatal disease for dogs, cats, and other mammals, so read our Williamsburg Animal Clinic teams tips on how to protect your pet from this serious condition.

What is heartworm disease in pets?

Heartworm disease is caused by the parasitic worm Dirofilaria immitis, which is transmitted to pets through an infected mosquito’s bite. When a mosquito carrying heartworm larvae (i.e., microfilaria) bites your pet, the larvae enter your furry pal’s bloodstream and develop into adult worms over several months. These adult worms can grow up to a foot long and take up residence in your pet’s heart, lungs, and blood vessels, causing serious and potentially fatal damage.

After reaching adulthood within six to seven months, heartworms begin reproducing, filling the affected pet’s bloodstream with microfilaria. When a mosquito feeds on the infected pet, the insect ingests microfilaria, which then travel along their life-cycle path to reach the infective larval stage. At this point, the mosquito can infect a wild animal or pet during mealtime.

Heartworm disease is not directly contagious among pets. However, knowing the heartworm status of nearby pets alerts you to the disease’s prevalence in your area. This information makes you aware that other pets and wildlife are acting as parasitic reservoirs waiting to infect your furry friend.

What are heartworm disease signs in pets?

Heartworm disease signs can vary between dogs and cats, and they may not become apparent until the disease has advanced. In dogs, common heartworm disease signs include:

  • Persistent cough that worsens over time
  • Fatigue 
  • Decreased appetite
  • Weight loss
  • Swollen abdomen caused by fluid accumulation

Dogs who develop severe heartworm infections can suffer from caval syndrome, a condition in which a mass of heartworms occludes blood flow within the heart. Prompt surgical removal is necessary, but the prognosis is poor.

In some cases, sudden death may be the only sign an infected cat displays, making regular prevention incredibly important. In cats, heartworm disease signs may include issues such as:

  • Coughing or wheezing
  • Gagging
  • Periodic vomiting
  • Appetite loss
  • Weight loss
  • Difficulty breathing
  • Asthma-like attacks
  • Lethargy
  • Incoordination
  • Sudden collapse

How is heartworm disease diagnosed in pets?

Diagnosis typically involves blood tests to detect the presence of heartworm microfilaria or proteins produced by adult female heartworms. Additional blood work, X-rays, and potentially a cardiac ultrasound are also essential for determining the disease’s extent and severity.

How is heartworm disease treated in pets?

Treatment for heartworm disease can be challenging, costly, and potentially dangerous, particularly in advanced cases. In dogs, treatment typically involves a series of arsenic-based injections to kill the adult worms, along with strict exercise restriction and supportive care for several months. In cats, treatment is often focused on managing the symptoms and preventing further complications, as no approved heartworm treatment exists for cats.

How can I prevent heartworm disease in my pet?

As with many diseases, prevention is the best approach to help your pet avoid contracting heartworm disease. Fortunately, several effective preventive measures are available for dogs and cats, including:

  • Monthly oral or topical medications — These medications work by killing the heartworm larvae before they can develop into adult worms.
  • Biannual or annual heartworm injections — These injectable medications provide long-lasting protection against heartworm disease.
  • Mosquito control — Reducing mosquito populations around your home and yard by eliminating standing water and planting insect-repelling flowers and plants can help limit your pet’s exposure to potential heartworm carriers and can be used in conjunction with year-round heartworm preventives to protect your pet.

Keep in mind that pets who spend most, if not all, of their time indoors are still at risk for heartworm disease, as mosquitoes can easily find their way inside. Consult with our Williamsburg Animal Clinic team to determine the most effective prevention plan for your pet based on your location, lifestyle, and risk factors.