Humans aren’t the only ones who enjoy Florida’s tropical paradise—mosquitoes do, too. This means a higher incidence of potentially fatal heartworm disease for our beloved dogs and cats. While heartworm disease is almost completely preventable, Florida cases still continue to climb, because of misinformation about transmission, warning signs, prognosis, and prevention.

The Boca Midtowne Animal Hospital team wants to equip pet owners with the knowledge to protect their pets and take back paradise from these pesky parasites. Join us as we debunk the most common myths about heartworm disease and prevention. 

MYTH: Heartworm disease affects only outdoor pets, so my indoor pets are low-risk for developing heartworm disease.

FACT: Mosquitoes are present indoors, and so is heartworm disease

Heartworm disease occurs in both indoor and outdoor pets. Mosquitoes can slip in through open doors and window screens to feed on unprotected indoor-only pets. Dogs who go outside to eliminate and exercise are vulnerable to mosquito bites, and can carry infective mosquitoes inside to other pets—only one bite can transmit heartworm disease.

Once they bite, mosquitoes carrying Dirofilaria immitis—the microscopic, early heartworm stage—inject the larvae into the bite wound as they feed. Once beneath the skin, the immature worms enter circulation and migrate to the pet’s lungs and heart. Over a five- to six-month period, the worms grow into adults and cause congestion, inflammation, and irreversible damage to the heart and large pulmonary vessels. 

MYTH: Heartworm disease is easy to identify in pets.

FACT: Pets do not show visible signs until the disease is well-established.

Pets in early heartworm disease stages will look and behave normally. Signs may appear only when the worms have grown big enough to trigger inflammation of the heart tissue and vessel walls. Signs in dogs may include:

  • Persistent cough that worsens with exertion
  • Appetite loss
  • Exercise intolerance
  • Fatigue after moderate activity
  • Weight loss
  • Pot-bellied appearance, caused by congestive heart failure in the late stages

Cats can suffer from heartworm associated respiratory disease (HARD), which may resemble other common feline respiratory illnesses, such as asthma. Additional signs are equally vague and may include:

  • Coughing
  • Appetite loss
  • Weight loss
  • Occasional vomiting
  • Difficulty walking
  • Seizures
  • Sudden death that, unfortunately for cats, is often the only sign

MYTH: If my dog is receiving heartworm preventives, they do not need an annual heartworm test.

FACT: Annual heartworm testing is recommended for all pets.

No medication is 100% effective 100% of the time, and pets on preventives do occasionally test positive for adult heartworms. A “protected” pet may show a positive result because of missed doses, stopping and resuming preventives without a heartworm test, or, less frequently, heartworms resisting the preventive. The reason for such resistance is not entirely understood, but these break-through infections, thankfully, are uncommon. Consistent heartworm preventive use and annual testing is always your pet’s best defense.

MYTH: Heartworm disease treatment is simple and safe for pets.

FACT: Treatment for dogs is expensive and requires prolonged cage rest to prevent complications, and no heartworm treatment exists for cats.

Occasionally, pet owners confuse heartworm prevention with heartworm treatment, and choose a “wait and see” approach to their pet’s health. Unfortunately, this misunderstanding can lead to heartache, as heartworm disease treatment can be cost-prohibitive for some dog-owners, and no treatment is available for cats.

Treatment in dogs requires a series of deep intramuscular medication injections in the lower back. Strong analgesics are administered during treatment to negate the pain and soreness from the deep, high-volume injection. Dogs undergoing treatment must be kept calm and crated for up to six weeks to prevent complications, such as deadly vascular clots or blockages formed by the dead and dying worms.

MYTH: Cats do not get heartworm disease.

FACT: Cats are susceptible to a heartworm disease, but are affected differently.

Cats are not the preferred blood meal for some mosquitoes, and not ideal hosts for heartworms. However, they can be infected and suffer from heartworm disease. While cats infected with heartworms typically rarely hold microfilariae and only a few adult worms, the adults that migrate to the lungs can cause initial signs that resemble asthma or bronchitis, leading to misdiagnosis. Unfortunately, the only other common feline heartworm disease sign is sudden death.

Since no safe treatment exists for heartworm disease in cats, year-round preventives are essential.

MYTH: Heartworm preventives are necessary only in the spring and summer months.

FACT: Year-round prevention is key to a successful heartworm prevention plan.

Our mild winters do not effectively kill off mosquito populations—their tell-tale buzz can be heard year-round. Oral heartworm preventives work retroactively, by killing any circulating juvenile heartworms (i.e., microfilariae) that may have been transmitted in the previous month. Therefore, pausing monthly preventives makes your pet vulnerable to an infection that will worsen during the subsequent months. 

For the ultimate in convenient and comprehensive prevention, Proheart 12 for dogs provides 12 months of continuous protection from a single injection—no more forgotten doses! Speak with Dr. Man to determine which heartworm prevention product is best for your pet.

Understanding how to provide the best care for your pet can be a challenge—especially in the internet age when myth and fact seem interchangeable. At Boca Midtowne Animal Hospital, we pride ourselves on being your trusted resource for veterinary care and expertise. Contact us  with any additional questions about heartworm disease, or to discuss your pet’s prevention needs.