Rocklin Ranch Veterinary Hospital’s Blog

Heartworm is one of those diseases you don’t ever want your dog or cat to get. When a pet has heartworms, long, noodle-like worms quite literally live in their heart. Treating the disease can be a grueling process for your dog—and you. The best way to treat heartworms is to prevent your dog or cat from getting them in the first place. April is Heartworm Awareness Month, which gives us the perfect opportunity to share some of the things we want you to know about this disease. 

What is Heartworm? 

Heartworm is a parasite called Dirofilaria immitis. Dogs are a natural host for this parasite. This means that the worms can grow into adults and reproduce inside your dog’s body. (Gross, right?) Dogs can’t give each other heartworms, though, and neither can cats. Heartworms can only be spread by mosquitoes. 

When a mosquito bites an infected dog, it ingests heartworm offspring, called microfilariae. The microfilariae turn into infective larvae after 10-30 days inside the mosquito’s belly. Then they travel into the mosquito’s proboscis, which means that when it bites another dog, it deposits heartworm larvae into the bite wound. The larvae travel through the bloodstream into your dog’s heart, lungs, and blood vessels. Here, they’ll mature into adults, reproduce, and deposit more microfilariae into your poor dog or cat’s body. 

Signs of Heartworm 

Heartworm disease has four stages as outlined by the FDA, each with distinct symptoms: 

• Class 1: No symptoms or mild symptoms, like a light cough.
• Class 2: Intermittent coughing, excess fatigue after exercising, and other moderate symptoms.
• Class 3: Difficulty breathing, persistent coughing, and fatigue after light activity are common in this stage. 
• Class 4: Also known as caval syndrome, this is the most serious stage of heartworm disease. It occurs when the mass of worms blocks normal blood flow to the heart. The only treatment is emergency surgery to remove the worms. Even then, many dogs with caval syndrome don’t make it. 

If your dog or cat shows any Class 1 or 2 signs of heartworm, bring them in for a checkup. The  team at Rocklin Ranch Veterinary Hospital can perform advanced diagnostic tests to see if your dog has heartworm disease or if another issue is at play. 

For Class 3 or 4 symptoms, get your pet to an emergency veterinary hospital right away. We offer emergency services during our normal business hours. 

How to Prevent Heartworm

Giving your pet their heartworm prevention medication on time and as directed is the only way to prevent heartworm. Some pets take monthly pills or topical ointments. Others receive once or twice-yearly shots. As per FDA regulations, your veterinarian must prescribe the medication to your pet. Puppies and kittens should begin taking preventive medication at around 6-8 weeks old. 

If you adopt an older pet or need to restart heartworm medication after forgetting it for a while, your pet will need to be tested for heartworms before starting preventive medication. Dogs and cats that don’t have heartworms can then begin their preventive prescription. If your dog or cat tests positive for heartworm disease, your vet will put together a treatment plan. 

Even the best preventive medications can fail, however. We recommend annual heartworm testing to make sure your pet remains heartworm-free. You should also bring your pet in for a test if you accidentally miss a dose, switch heartworm medications, or travel to a place known for having lots of heartworm infestations. 

Is your dog or cat ready for a heartworm checkup? Schedule an appointment for a heartworm test at Rocklin Ranch. With our in-house pharmacy, we can provide heartworm prevention or treatment medication on the spot.