Heartworm disease is caused by a parasitic worm, Dirofilaria immitis, that lives in the heart and blood vessels of infected dogs. We talk to pet owners about the importance of protecting their pets from this deadly parasite every day at Stone Ridge Veterinary Medical Center. You may think you know the facts about this dangerous disease, but is your pet adequately protected? Refresh your memory with these nine facts, and ensure your pet stays healthy.

#1: Heartworms are transmitted by mosquitoes

Texas has more than its fair share of these annoying bloodsuckers, and some are carrying heartworms they can transmit to your pet. A mosquito that bites an infected dog picks up microscopic heartworm larvae with its blood meal, the larvae develop in the mosquito’s gut, and the mosquito transmits the heartworms to other animals it bites. Heartworms passed to a bird, rabbit, or human simply die, but they survive in a dog, the heartworm’s preferred host, and disease develops.

#2: Heartworm disease has been reported in all 50 states

Although mosquitoes are most prevalent in hot, humid climates, they buzz their way into every part of the U.S.—including Alaska. With our long, humid summers, and droves of mosquitoes, you may not be surprised that Texas had the highest number of heartworm cases last year—more than 6,300. Heartworm disease is definitely a major threat for Texas pets, including yours.  

#3: Wild animals, stray pets, and neighborhood dogs can all serve as infection reservoirs

To transmit heartworms, a mosquito must first bite an infected host. If you live in a high-end subdivision, you may think no nearby animals carry heartworm disease to put your dog at risk—think again. The canine population that heartworms prefer includes wolves, coyotes, and foxes, and most rural and suburban areas have a thriving wildlife population that serves as an infection reservoir for nearby pets. City pets are no safer, as stray, unprotected dogs can serve as reservoirs. Also, consider that wind can blow mosquitoes for miles, from rural areas to your gated community. 

#4: Heartworm disease can be disastrous for your dog

Heartworm disease causes significant heart and lung damage, and death, without treatment. Once inside your pet’s body, the few heartworms transmitted by one mosquito bite travel to her lung vessels, mature, and start replicating. With each generation, more juvenile worms mature and reproduce, and can lead to a burden of up to 250 worms. The worms’ presence interferes with normal blood flow, triggers heart and lung inflammation, and causes long-term damage. A heartworm infection does not spontaneously resolve, and the associated disease will progress to death, without treatment. 

#5: Cats develop a different form of heartworm disease

Cats are an atypical heartworm host. The few worms that are transmitted to a cat, typically one to three, often don’t survive to adulthood, and those that do cannot reproduce. However, a few immature worms in a cat can incite significant inflammation, and cause heartworm-associated respiratory disease (HARD). Affected cats may have asthma-like symptoms, but many show no signs, and may collapse and die suddenly.  

#6: Heartworm disease is often silent

While you may think the presence of 12-inch-long worms in a dog’s heart and lungs would cause obvious clinical signs, the fact is, many dogs show few heartworm disease signs. The lethargy, vomiting, and coughing that may develop once a significant heartworm burden accumulates may not arouse much suspicion, and can be attributed to a number of other diseases. By the time owners realize their dog is sick, the disease has typically progressed to an advanced stage.

#7: Heartworm disease treatment is difficult for dogs

Heartworm disease treatment includes a medication to kill adult worms that is administered by intermittent injections deep into a dog’s back muscles. Additional medications are administered to kill immature worms, decrease inflammation, and kill bacteria the worms carry. During treatment, dead worms can become lodged in a pet’s lung vessels, and cause a deadly pulmonary embolism. The higher a dog’s worm burden, and the more advanced her disease, the more likely is this complication. Throughout treatment, dogs must be restricted to cage rest, with controlled leash walks for bathroom breaks only, to minimize this risk. 

No medication that kills heartworms in cats is available, and treatment focuses on managing symptoms and reducing inflammation. 

#8: Annual heartworm testing is a critical part of your pet’s wellness care

We screen pets for heartworm disease during their annual wellness appointment, to ensure they haven’t picked up an infection in the past year. Yearly heartworm testing is critical, because one missed heartworm preventive dose, or a dose that your pet spits out or vomits up, can leave your pet unprotected. If your pet is not currently on a preventive, we will perform a heartworm test to ensure she is negative, before starting prevention. We may recommend a second test six months later, as the test detects only adult female worms, and not juvenile worms, which require approximately six months to mature. 

#9: Heartworm disease is easily preventable

Fortunately, this deadly disease is easily preventable with regular administration of a preventive medication. Some pet owners choose monthly beef-flavored chewable tablets, which pets gobble up like treats. We also offer Proheart-12, an injection administered once a year that protects your dog for 12 months, eliminating the need to remember a monthly medication. Prevention is also available for cats, and regular administration is critical, since no treatment is available. All pets should receive year-round heartworm prevention, because mosquitoes are active all year long in the Lone Star State. A Stone Ridge Veterinary Medical Center team member can help you choose a preventive that fits your pet’s needs.

Is your pet overdue for an annual heartworm test or preventive refill? Call us to schedule this important appointment, so your pet is protected from heartworm disease.