Heartworm disease is a deadly but completely preventable condition affecting dogs. Yet, despite the ready availability of effective preventives, the disease continues to thrive, and is now considered endemic in all 50 states, Puerto Rico, the Virgin Islands and right here at home in Guam. 

Our warm tropical climate makes the island a natural paradise for disease-carrying mosquitoes—and, therefore, a heartworm disease hotbed. But, if prevention is simple, why is heartworm diagnosis more common than ever? Let’s take a look with this heartworm prevention fact guide from Guam Pet Hospital. 

#1: Heartworm disease is carried and transmitted to pets by infected mosquitoes

Pet owners may not give prevention products because they believe their pet is not at risk. In reality, all pets on the island are vulnerable to heartworm disease. Whether they live indoors or outdoors, dogs need only one bite from an infective mosquito for heartworm disease microfilaria to be transmitted into the bloodstream. Mosquitoes can easily slip inside through doorways and window screens or ride in on pets or people’s clothing. Once inside the home, your indoor-only pet may be its next meal. 

#2: Heartworm disease prevention must be consistent to be effective

Pet owners may accidentally forget to give their pets their monthly prevention, or stop the medication when the prescription runs out. Unfortunately, this time gap allows the heartworms to grow and mature, during which time they become no longer susceptible to the medication in monthly preventives—so if you do eventually restart your pet’s heartworm preventive, you may be too late.

Some simple ways to ensure you always remember to give your pet’s medication include:

  • Calendar — This classic method still works! Keep a 12-month chart near your pet’s food, so you’ll see it every day.
  • Use your planner — Book out your pet’s preventive right alongside your everyday to-do list. Pre-fill every month, so you don’t forget throughout the year.
  • Phone reminders — Use your calendar app to schedule the entire year—with only a few clicks, you have a recurring reminder.

#3: Pets infected with early heartworm disease may not show any signs

Dogs with early stage heartworm disease often look and behave normally. Only when the worms have grown in length and size do they irritate the lining of your pet’s vessels and heart, and the irritation triggers visible signs such as coughing, exercise intolerance, and fatigue. Late stage disease is clearly apparent, with dogs demonstrating severe lethargy, weight loss, collapse, and a swollen abdomen caused by heart failure.

Cats can get heartworm too but much less commonly than dogs. Cats experience heartworm disease differently and host few adult heartworms, they may exhibit only mild signs, or no signs at all. Unfortunately for cats, the first and only heartworm disease sign is often sudden, unexplained death.

#4: Yearly heartworm disease testing is essential to ensure your dog’s health

Some owners are reluctant to comply with annual heartworm testing, which they feel is unnecessary or excessive when their pet is on a preventive. However, the yearly test is essential for several reasons:

  • Missed doses — One missed or forgotten dose can allow infection to take hold. Missed doses aren’t always caused by the owner’s forgetfulness—pets may also vomit up their preventive, or one dog may steal a dose away from their fellow house pet.
  • Starting prevention — Before your adult pet can begin heartworm prevention protocol, a negative test is necessary, to ensure they are disease free. 
  • Product failure or drug resistance — Although extremely rare, preventive failure can sometimes occur and allow a “breakthrough” infection. Also, the possibility that certain heartworm strains are developing resistance to ivermectin, a common preventive ingredient, has been suggested. While such an occurrence is unlikely, testing is still the only safeguard against hidden infection. 

Because cats have small adult worm infections (i.e., only one to two worms), they may not register on a heartworm test. Therefore, at this time, testing is only required for dogs. 

#5: Heartworm prevention is more affordable and safer than treatment

Owners may avoid giving heartworm prevention because they believe they will treat their pet when and if they become ill. Unfortunately, this decision is often made without fully understanding the nature and power of heartworm disease.

Treatment for dogs is available, but is expensive, painful, and prolonged, involving four to six months of strict crate rest while the worms die off. In dogs with a heavy worm population, the treatment process can be life-threatening if the dying worms form a clot in the major vessels. For additional treatment information, visit our previous blog post.

Unfortunately, no safe treatment is available for feline heartworm disease. Once cats are infected, the only option is medical management for their clinical signs. 

Protect your pet, protect yourself from heartache

It is estimated that Guam has as many as 60,000 stray dogs, or boonies. These dogs are not on heartworm or tick prevention, thus they are a reservoir of infection, and put our domestic dogs at high risk. We diagnose tick-borne diseases every day, and heartworm disease weekly, in our patients—don’t let your dog be one of them! Once monthly treatment with Simparica Trio will protect your dog from these terrible, yet avoidable diseases, and protect you from having to pay for costly treatment. By increasing the number of pets on heartworm prevention, Guam Pet Hospital hopes to protect your pet from these terrible diseases.

Contact our team for heartworm preventive recommendations, or to schedule your pet’s heartworm test.