## The "invisible" disease that kills thousands of dogs every year

In Italy, every year, **thousands of dogs die or are diagnosed** with heartworm disease. Yet, it is a **completely preventable** disease with a simple monthly prophylaxis.

Knowing it saves lives.

## What is heartworm

**Heartworm** (Dirofilaria immitis) is a **parasitic worm** that lives in the right heart and pulmonary arteries of dogs.

**Adult size**:
- Male: 12-18 cm.
- Female: 25-30 cm.

A dog can host **dozens** of adult worms.

## How it is transmitted

**Only through mosquitoes**.

**Cycle**:
1. A mosquito bites an infected dog.
2. It takes in microscopic larvae (microfilariae) from the blood.
3. Larvae develop in the mosquito.
4. The mosquito bites a healthy dog.
5. Injection of the larvae into the blood.
6. Larvae **migrate** to the heart in 6 months.
7. They become adult worms, living in the heart for **5-7 years**.

**Distribution in Italy**:
- **Po Valley**: very high endemicity (>50% of unprotected dogs infected).
- **Central Italy**: medium-high.
- **South**: medium.
- **Alpine**: low (for now).

With climate change, the endemicity is **expanding north**.

## The symptoms

**Early stage (asymptomatic)**:
- 6 months - 2 years: no symptoms.
- The dog appears perfectly healthy.

**Intermediate stage**:
- **Mild cough** after exercise.
- **Early fatigue**.
- **Reluctance to exercise**.

**Advanced stage**:
- Severe chronic cough.
- Difficulty breathing.
- Fainting.
- Swollen abdomen (ascites due to right heart failure).
- Profound lethargy.
- **Sudden death** (common in the final stage).

**Final stage (caval syndrome)**:
- Extremely high number of worms block the heart.
- Hemolytic anemia.
- Death within days if not emergency surgery.

## The diagnosis

**Blood tests**:
- **Antigen test** (SNAP test): rapid (10 minutes), in veterinary practice.
- **Knott test**: looks for microfilariae in the blood.
- High sensitivity after 7 months from infection.

**Chest X-ray**:
- Shows enlargement of the right heart.
- Thickened pulmonary vessels.

**Echocardiography**:
- Visualizes worms in the heart chambers.
- Quantifies severity.

**Blood tests**:
- Anemia.
- Liver/kidney dysfunction.

## The therapy

**Standard treatment**:

**Step 1**: stabilization.
- Cortisone to reduce inflammation.
- Antibiotics (doxycycline) to kill Wolbachia (endosymbiotic bacteria of the worms).
- 4 weeks of preparatory therapy.

**Step 2**: killing adult worms.
- **Melarsomine** (Immiticide): injectable intramuscular drug.
- 2-3 doses spaced out.
- Cost: €800-2,000 for a complete cycle.

**Step 3**: confinement.
- **3 months of absolute rest**: no walks, no running.
- Rest is essential: dead worms in circulation can cause **pulmonary embolism** if the dog is agitated.

**Step 4**: follow-up testing.
- 6 months later: antigen test to check recovery.
- 12 months: second test.

**Recovery rate**: 85-95% if treated early.

**Mortality**: 5-15% (risk of pulmonary embolism during therapy).

## Prevention: a few euros, a life saved

**Monthly prophylaxis**:

**Tablets**:
- **Cardotek-30**: monthly ivermectin.
- **Heartgard**: monthly ivermectin.
- Cost: €8-12 per tablet.

**Spot-on**:
- **Advantix Multi** (combines anti-heartworm with antiparasitic).
- **Stronghold**: includes heartworm.
- Cost: €10-15 per vial monthly.

**Annual injection**:
- **Proheart 12** (moxidectin): a single injection per year.
- Very convenient (no monthly tablets to remember).
- Cost: €80-120 per year.

**Frequency**: monthly from May to November (temperate zones) or year-round (warm areas/tourism).

## The "closing tablet" rule

**Important**: monthly prophylaxis **kills the larvae** ingested in the last 30 days.

So:
- Start of mosquito season = start of prophylaxis.
- **Last dose**: 1 month after the end of the mosquito season.

If the last mosquito is in October: last tablet in November.

## What to do before starting prophylaxis

**Mandatory antigen test**:
- Before starting prophylaxis.
- Ensure that the dog **is not already infected**.

**Why**: giving prophylaxis to an infected dog can cause:
- Severe allergic reaction (anaphylaxis) due to massive killing of microfilariae.
- Life-threatening danger.

**Conclusion**: test always before the first treatment.

**Subsequent tests**:
- Every 12 months (even if protected).
- For safety.

## The costs

**Annual prophylaxis**:
- Monthly tablets: €50-100.
- Spot-on: €80-130.
- Proheart 12 (annual injection): €80-120.

**Annual test**: €30-50.

**Total prevention**: €80-180/year.

**Treatment if contracted**: €1,500-3,500 + risk.

Preventing = 95% savings + healthy dog.

## The breeds at highest risk

**All breeds**: dogs of any breed, sex, size can contract heartworm.

**Increased risk for**:
- Dogs living a lot outdoors.
- Dogs in endemic areas (Po Valley).
- Sporting dogs (more physical exercise = more blood pumped = higher risk of developing larvae).
- Unprotected dogs.

**Breeds sensitive to Ivermectin**:
- Collies and similar breeds.
- Australian Shepherds.
- Old English Sheepdogs.

They require **specific dosages**: discuss with veterinarian.

## Myths to debunk

**Myth 1**: "Heartworm is only in the Po areas."
**False**: present throughout Italy, although concentrated in some areas.

**Myth 2**: "Indoor dogs don’t need prophylaxis."
**False**: even just 5 minutes outside to pee can bring mosquitoes.

**Myth 3**: "Heartworm shows up immediately."
**False**: the dog can be asymptomatic for years.

**Myth 4**: "Prophylaxis causes liver damage."
**Truth**: extremely rare at correct dosages.

**Myth 5**: "Once a year is enough."
**False**: only Proheart 12 is annual. Everything else is monthly.

## A thought-provoking story

**Case study**: a 5-year-old Labrador in Lombardy. Never protected from heartworm. Symptoms: mild cough + fatigue.

Diagnosis: 23 adult worms in the heart.

Treatment: 6 months of care, €3,000 in expenses, 90 days of absolute rest.

Outcome: dog healed but with damaged heart. Life expectancy reduced by 3-4 years.

**Cost of prevention that would have avoided all this**: €50 per year for 5 years = €250.

## The conclusion

Heartworm is one of the most dramatic and **most preventable** diseases in the canine world.

**Prevention cost**: €80-180/year.
**Treatment cost**: €1,500-3,500 + life risk.
**Cost of dead dog**: incalculable.

One tablet a month, or one injection a year: saves your dog's heart.

Discuss it with your veterinarian. Start now. Don't wait.