💉 Dog Heartworm Testing: What Every Pet Parent Should Know – 2025 🐶

Hello caring dog guardians! 😃 I’m Dr Duncan Houston BVSc. Heartworm disease is a potentially fatal but preventable condition transmitted by mosquitoes. Accurate testing is essential to keep your pup protected and ensure timely treatment. In this detailed guide, we’ll walk through antigen and microfilaria testing, timing, result interpretation, retesting protocols, and how Ask A Vet supports you in 2025. Let’s safeguard your furry friend! 🛡️

1️⃣ Why Test for Heartworm?

Heartworm infection, caused by Dirofilaria immitis, affects the heart and lungs. Early detection allows for less invasive treatment and better outcomes. The American Heartworm Society (AHS) emphasizes annual testing even in dogs receiving preventives :contentReference[oaicite:2]{index=2}.

2️⃣ Two Tests You Need

• Antigen Test

• Detects proteins from adult female worms, ~5–7 months after infection :contentReference[oaicite:3]{index=3}.
• Highly accurate, but false negatives can occur with low worm burden, all-male infections, or early infections :contentReference[oaicite:4]{index=4}.
• If positive, confirm with a second test before treatment :contentReference[oaicite:5]{index=5}.

• Microfilaria Test

• Identifies circulating larvae using methods like Knott’s concentration :contentReference[oaicite:6]{index=6}.
• Recommended alongside antigen test, especially when prevention history is unknown or results are ambiguous :contentReference[oaicite:7]{index=7}.
• Can detect cases when antigen test is negative due to immune complexes or absence of adult females :contentReference[oaicite:8]{index=8}.

3️⃣ When Should You Test?

• Start annual testing once dogs are older than 7 months—this allows for development of detectable adult worms :contentReference[oaicite:9]{index=9}.
• Test before initiating preventives to avoid missing early infections :contentReference[oaicite:10]{index=10}.
• If preventive doses are missed, repeat testing ~7 months afterward :contentReference[oaicite:11]{index=11}.

4️⃣ Interpreting Test Results

• **Antigen– / Microfilaria–**: likely no infection; maintain annual testing.
• **Antigen + / Microfilaria –**: may be early or occult female infection—confirm with repeat test or extended diagnostics :contentReference[oaicite:12]{index=12}.
• **Antigen – / Microfilaria +**: possibly blocked antigen; repeat testing with heat-treated serum or advanced diagnostics :contentReference[oaicite:13]{index=13}.
• **Antigen + / Microfilaria +**: confirmed infection—vet will assess disease severity and initiate a treatment plan.

5️⃣ Confirming Positive Cases 📋

When either test is positive, veterinarians generally:

• Confirm with a second antigen test using different methods or providers :contentReference[oaicite:14]{index=14}.
• Perform blood work, X-rays, or ultrasound to evaluate disease impact :contentReference[oaicite:15]{index=15}.
• Start a tailored adulticide therapy after stabilization :contentReference[oaicite:16]{index=16}.

6️⃣ What If My Dog Is Positive?

Treatment typically involves:

• Exercise restriction to reduce embolism risk :contentReference[oaicite:17]{index=17}.
• Stabilization if cardiopulmonary signs are present.
• Medication with adulticide (e.g., melarsomine), doxycycline (to target *Wolbachia*) and a preventive for microfilariae :contentReference[oaicite:18]{index=18}.
• Monthly heartworm prevention resumed after treatment :contentReference[oaicite:19]{index=19}.

7️⃣ Monitoring & Follow-Up

• Re-test antigen ~6 months after completing adulticide treatment to confirm clearance :contentReference[oaicite:20]{index=20}.
• Continue annual antigen + microfilaria testing even on prevention :contentReference[oaicite:21]{index=21}.

8️⃣ Preventive Measures

• Round-the-year preventives (ivermectin, milbemycin, moxidectin, selamectin) are essential :contentReference[oaicite:22]{index=22}.
• Adding tick and mosquito protection enhances defense in endemic regions :contentReference[oaicite:23]{index=23}.
• Preventives effective in 99% of cases—ensure consistent dosing and testing :contentReference[oaicite:24]{index=24}.

9️⃣ When Ask A Vet Can Help 📲

Ask A Vet supports you with:

• Clarification on test types and the best timing for your dog.
• Guidance on interpreting unusual results and next steps.
• Assistance deciding between in-clinic vs referral testing.
• Supportive advice during treatment, exercise restriction, medication administration, and follow-up.
• Year-round reminders to keep your pup on schedule. 🐾

🔟 Quick Reference Table 📊

💡 Dr Duncan’s Final Thoughts

Heartworm testing safeguards your dog from a potentially deadly disease. Using both antigen and microfilaria tests annually helps catch infections early, even when prevention lapses occur. With prompt treatment and consistent care, most dogs recover fully. Ask A Vet is here 24/7 to guide you—from understanding test results to navigating treatment and prevention—all to protect your loyal companion’s health and happiness. 😊🐾

Dr Duncan Houston BVSc — your partner in parasite prevention. Visit AskAVet.com and download our app for expert support anytime. 📱