Heartworm in Dogs and Cats: Diagnosis, Treatment & Prevention
Southern Ocean Animal Hospital | Advanced Heartworm Care in Tuckerton, NJ
TL;DR (Too Long; Didn’t Read)
Heartworm disease is a serious, potentially fatal condition caused by parasites that live in the heart and lungs of dogs, cats, and other animals. Mosquitoes transmit it and can cause long-term damage even before symptoms appear.
- Dogs can be treated with a multi-step protocol (melarsomine, doxycycline, and rest), but early detection is key.
- Cats have no approved treatment—supportive care and prevention are critical.
- Monthly preventatives and annual testing are the most effective forms of protection.
- Southern Ocean Animal Hospital features on-site labs and a pharmacy, allowing for immediate diagnosis and treatment.
ELI5 (Explain Like I’m 5)
Imagine a tiny mosquito bites your dog or cat. That mosquito can leave behind invisible worms that grow big inside your pet’s heart and lungs. These worms hurt their breathing and energy. In dogs, we can use medicine to kill the worms, but it’s a long process. In cats, there’s no safe way to kill them, so we have to help them feel better and stop new worms from coming. The best way to keep pets safe is with monthly medication and yearly check-ups to catch any issues early.
Essential Points at a Glance
- 🦟 Mosquitoes transmit heartworms.
- 🐶 Dogs can be treated with melarsomine, doxycycline, and strict rest.
- 🐱 Cats cannot be cured—supportive care is the only option.
- 🧪 Diagnosis involves blood tests, X-rays, and ultrasounds.
- 💊 Monthly preventatives are safe, affordable, and essential.
- 🧫 Southern Ocean Animal Hospital has in-house labs and a pharmacy for fast testing and treatment.
What Is Heartworm Disease?
Heartworm disease is caused by Dirofilaria immitis, a parasitic worm that lives in the heart, lungs, and associated blood vessels of affected animals. It primarily affects dogs, but also occurs in cats and ferrets, and is spread through the bite of an infected mosquito.
Once inside the host, the heartworm larvae mature over a period of 6 months into adult worms that can grow up to 12 inches long, causing severe inflammation, lung disease, heart failure, and even death.
How Heartworm Is Transmitted
- A mosquito bites an infected animal and picks up heartworm larvae (microfilariae).
- The larvae mature inside the mosquito for 10–14 days.
- When the mosquito bites another animal, it transfers the larvae into the bloodstream.
- The larvae migrate to the heart and lungs, where they grow and reproduce.
Diagnosing Heartworm in Dogs and Cats
🐶 Diagnosis in Dogs
1. Antigen Test
- Detects proteins from adult female heartworms in the bloodstream.
- The most common and reliable test for dogs.
2. Microfilaria Test
- Detects immature heartworms (larvae) circulating in the blood.
- Confirms active infection.
3. Additional Diagnostics
To evaluate the severity of the disease:
- Complete Blood Count (CBC): Checks for anemia or infection.
- Chemistry Panel: Assesses organ function.
- Chest X-rays: Reveal heart enlargement or lung damage.
- Ultrasound (Echocardiography): Visualizes the heart and its function.
🐱 Diagnosis in Cats
Diagnosing heartworm in cats is more difficult:
- Antibody Tests: Detect the cat’s immune response to heartworm exposure.
- Antigen Tests: Often negative in cats, due to low worm burdens or single-sex infections.
- Chest X-rays and Echocardiograms are often more helpful than blood tests.
💡 Southern Ocean Animal Hospital uses state-of-the-art diagnostic tools such as the EDAN Acclarix AX3 ultrasound, digital X-rays, and in-house ELISA tests for fast, accurate diagnosis.
Symptoms of Heartworm Disease
In Dogs:
- Persistent cough
- Fatigue after light activity
- Reduced appetite
- Weight loss
- Difficulty breathing
- Swollen belly from fluid
- Sudden collapse (in severe cases)
In Cats:
- Coughing or wheezing
- Vomiting (unrelated to food)
- Weight loss
- Lethargy
- Sudden collapse or sudden death (even in asymptomatic cats)
Treating Heartworm Disease
🐶 Treatment in Dogs
Treatment is intensive, and early diagnosis improves outcomes.
- Melarsomine Injections
- An FDA-approved arsenic-based adulticide.
- Administered in 2–3 injections to kill adult worms over 60 days.
- Doxycycline
- An antibiotic that kills Wolbachia, a bacteria that live inside heartworms.
- Reduces complications and improves treatment success.
- Heartworm Preventative
- Given monthly to kill immature larvae and prevent new infections.
- Strict Rest
- Vital during treatment. Dead worms can cause dangerous clots if the pet is too active.
- Supportive Care
- Anti-inflammatories, oxygen therapy, or hospitalization may be required for advanced cases.
💊 Southern Ocean Animal Hospital’s on-site pharmacy provides all necessary medications quickly and safely, eliminating delays in care.
🐱 Treatment in Cats
There is no approved adulticide treatment for heartworms in cats. Instead, we manage symptoms and inflammation:
- Corticosteroids
- Reduce lung inflammation and coughing.
- Bronchodilators
- Help cats breathe more comfortably.
- Supportive Care
- Includes oxygen therapy or hospitalization in severe cases.
- Heartworm Prevention
- Essential to prevent reinfection.
Prevention: The Best Defense
💊 Monthly Heartworm Preventatives
- Highly effective when used consistently
- Available as chewables, topicals, and injections
- Also, protect against other parasites like fleas, ticks, and intestinal worms
- Safe for puppies and kittens as young as 6–8 weeks
Southern Ocean Animal Hospital offers trusted brands like Interceptor Plus, Heartgard, Revolution, and ProHeart (injectable).
🧪 Annual Testing
Even pets on preventive care should be tested once a year. Why?
- Preventatives can fail due to missed doses, vomiting, or drug resistance
- Early detection = easier and more effective treatment
- Testing is quick and minimally invasive
Timeline of a Typical Heartworm Case in Dogs
| Stage | Event |
|---|---|
| Day 0 | Mosquito bite introduces larvae |
| Day 1–180 | Larvae migrate and mature into adults |
| 6–7 months | Dog becomes symptomatic |
| Month 7+ | Blood tests detect infection |
| Treatment Begins | Doxycycline + 2–3 melarsomine injections |
| 2–3 months | Strict crate rest during recovery |
| 3–6 months | Retesting to confirm success |
Example Case
Patient: Max, a 3-year-old Labrador retriever
History: Missed two months of heartworm prevention.
Symptoms: Mild cough and lethargy.
Tests: Antigen test + microfilaria test = positive.
Treatment:
- Doxycycline for 30 days
- 3-dose melarsomine protocol over 60 days
- Crate rest for 3 months
- Monthly prevention reintroduced
- Recheck 6 months later = negative!
Max made a full recovery thanks to early detection and immediate care from our veterinary team.
Common Questions
❓ What if I miss a dose of prevention?
Give it as soon as possible and call your vet. A missed dose could leave your pet vulnerable. Testing may be required before resuming prevention.
❓ Do indoor pets need prevention?
Yes. Mosquitoes can get indoors, and even indoor-only pets are at risk.
❓ Can I use dewormers for heartworm?
No. Standard dewormers kill intestinal worms—not heartworms. Heartworm preventatives are prescription-only for a reason.
❓ Is heartworm contagious between pets?
No. It only spreads through mosquito bites—not from pet to pet.
Why Choose Southern Ocean Animal Hospital?
At Southern Ocean Animal Hospital, we take heartworm disease seriously. Our commitment includes:
- 🧬 Advanced in-house diagnostics (blood tests, X-rays, ultrasound)
- 💊 Fully stocked in-house pharmacy for immediate treatment
- 🧪 Annual screening protocols and preventive care plans
- 🐾 Individualized treatment protocols based on age, size, and severity
- ❤️ Compassionate support for your pet’s recovery journey
Led by Dr. Daniel N. Pascetta, DVM, a graduate of The Ohio State University College of Veterinary Medicine, we bring the highest level of education, training, and experience to your pet’s heartworm care.
Schedule Your Pet’s Heartworm Test Today
Heartworm disease is preventable, but early detection is critical. Whether your pet is due for testing or showing concerning symptoms, Southern Ocean Animal Hospital is ready to help—right here in Tuckerton, NJ.
📞 Call us now or book online to protect your pet from one of the most dangerous—and preventable—parasites they’ll ever face.
Because every heartbeat matters. ❤️