Know Thy Enemy—Heartworm Disease and Prevention in Pets

Heartworm disease affects more than one million pets in the United States, and has been reported in all 50 states. Unfortunately, despite the availability of effective and safe heartworm prevention methods, this condition continues to infect dogs and cats, leading to debilitating and often deadly complications in the pet’s heart and lungs.

To best protect your pet, you need to understand the threat itself. Learn the basics of heartworm disease and prevention with this guide from Staples Mill Animal Hospital.

What is heartworm disease in pets?

Heartworm disease is a parasitic infection transmitted through the bite of an infected mosquito. When a mosquito bites your pet, microscopic heartworm larvae are injected beneath the skin. From there, they migrate through the tissues to the heart and lungs, where they mature into long, spaghetti-like worms. While infection size (i.e., worm burden) can vary, infected dogs may carry between 15 to 200 adult worms that can survive up to seven years. Cats are not natural hosts for heartworm disease, and therefore may carry only one or two mature worms that live only a few years. However, despite their smaller presence, their impact is equally devastating to the cat’s small cardiovascular system.

Heartworm disease damage in pets

In its earliest stages, heartworm disease is not noticeable, because the internal damage begins and signs become visible only when the worms mature. The presence of adult worms, which can measure up to 14 inches long, triggers inflammatory reactions inside your pet’s heart and in the lining of the large lung vessels. This trauma affects blood flow, while the tangled worm bodies can create additional resistance and life-threatening blockages.

Recognizing heartworm disease signs in pets

Initial illness signs may be nonspecific in dogs, while cats may show no signs at all. As the disease progresses, signs become more severe. From early to late-stage infection, signs may include:

  • In dogs:
    • Persistent cough
    • Reluctance to exercise
    • Decreased appetite
    • Abdominal swelling
    • Collapse
    • Seizures
    • Sudden death
  • In cats:
    • Episodic respiratory distress
    • Loss of coordination
    • Vomiting
    • Lethargy
    • Coughing
    • Sudden death

Heartworm disease diagnosis in pets

Because heartworm disease is a progressive condition, early diagnosis is important. The longer an infection continues, the more likely permanent cardiovascular damage will occur. While dogs are tested annually at Staples Mill Animal Hospital as part of their preventive care visit, screening tests for cats are not a yearly requirement, because the typical heartworm test detects female adult worms, and if a cat’s infection is caused by immature or only male worms, the result will be a false negative. However, if heartworm disease is suspected, additional testing, such as an antibody test, X-rays, or ultrasound, may be recommended.

In addition to annual testing, dogs and cats should be tested after a lapse in prevention, or if they are showing clinical signs.

Heartworm disease treatment in pets

If your pet tests positive for heartworm disease, options are available. Treatment for dogs includes a multi-step approach that includes:

  • Medication — Antibiotics are administered to treat a bacteria known as Wolbachia that live in heartworms. Since Wolbachia contribute to inflammation and worm population, eliminating these can reduce treatment complications.
  • Strict rest — Physical exercise can hasten heartworm damage, so dogs must be confined to a crate or small area for the treatment duration—up to eight weeks.
  • Injection series — Dogs receive a series of three painful intramuscular injections to kill off adult heartworms. They may receive strong analgesic medication to alleviate the pain. Cage rest must continue as the worms die and are removed from circulation.
  • Retesting — After treatment, your dog must begin a heartworm prevention protocol and be retested at specific intervals, to ensure the infection has been resolved.

Unfortunately, no safe treatment is available for feline heartworm disease. After diagnosis, supportive care may alleviate signs and prevent suffering, in hopes that the cat may outlive their heartworm burden.

Heartworm disease prevention in pets

While heartworm disease seems extremely worrisome, prevention is easy, effective, economical, and safe. Heartworm prevention works by eliminating any circulating microfilariae before they can mature, thereby preventing the dangerous cascade of inflammation, trauma, and vascular blockage. However, preventives must be given year-round (i.e., typically every 30 days) to be effective. Infection can take hold after only one missed or late dose.

In addition to year-round prevention, Staples Mill Animal Hospital recommends a yearly heartworm test, to ensure your pet is disease free and their prevention plan is working as intended. While heartworm prevention is incredibly effective, no product is 100% guaranteed, and if you believe you’ve missed a dose, heartworm testing can save your pet’s life, or prevent unnecessary suffering.

Selecting the right prevention for your pet

Heartworm prevention is available in a variety of forms, with the most common being oral chews or topical applications. Injectable heartworm medication is available for dogs in a 6- or 12-month duration, eliminating the need for monthly dosing.

Your veterinarian will make prevention recommendations based on your pet’s preferences—as well as your own—to ensure you use a safe and convenient product. After all, you’ll be more successful if you can administer a product easily every month, and your pet will be better protected.

Don’t let your pet fall victim to the merciless threat of heartworm disease. With year-round preventives and annual testing at Staples Mill Animal Hospital, you can be assured that the only thing in your pet’s heart is their unconditional love for you.

To schedule your pet’s heartworm test, or discuss prevention options and our recommendations, contact our team at Staples Mill Animal Hospital.