Last updated: 26 September 2026
A heartworm test detects antigen from adult female heartworms circulating in the blood. It takes about 6–8 months after an infective mosquito bite before the test can turn positive. That is why yearly screening is recommended: the best time is spring, before mosquito season and preventive treatment begin. If your dog did not receive prevention this year, it is also worth testing after the season. In Hungary, for example, a heartworm screen at a vet clinic costs HUF 10,000–18,000 plus an examination fee according to public 2026 price lists, while a home rapid test costs a fraction of that.
In this article we explain why screening is becoming more important in Central Europe, what the heartworm test does and does not detect, when to test, how to do it at home, and what to do if the result is positive. Symptoms and prevention are covered in a separate article: Heartworm in dogs and cats: symptoms, screening and prevention.
Why is heartworm screening becoming more important? The example of Hungary
Heartworm (Dirofilaria immitis) is spread by mosquitoes. The first locally acquired infection in a dog in Hungary was described in 2009, and the parasite has spread rapidly since. In a nationwide study carried out between March 2023 and February 2024, 1,071 dogs from all 19 Hungarian counties that had not received heartworm prevention in the previous year were examined:
- 17.0% were infected with heartworm, compared with 11.3% in the previous survey;
- the subcutaneous worm (Dirofilaria repens) was found in 10.2%;
- older and unneutered dogs were more likely to be infected;
- there was no meaningful difference between cities, small towns and villages.
Put simply: roughly one in six dogs living without prevention was infected. Infected dogs often show no symptoms for a long time, so heartworm can usually only be caught in time through screening.
What does the heartworm test detect and what not?
"Heartworm test" can mean several different tests. At home and in most clinics, an antigen rapid test is used. It looks for antigen from adult female worms in blood, serum or plasma.
| Test | What does it detect? | What is it good for? |
|---|---|---|
| Antigen rapid test (at home or at the clinic) | Antigen from adult female D. immitis | The primary method for yearly screening of dogs. Fast and very specific. |
| Knott test (lab or clinic) | Larvae (microfilariae) circulating in the blood | Distinguishes heartworm from the subcutaneous worm. A useful addition after a positive antigen test. |
| PCR (lab) | The worms' genetic material | Used for species identification and confirmation. |
| Chest X-ray, cardiac ultrasound | Changes in the heart and pulmonary vessels | In positive cases, assesses how severe the disease is. Especially important in cats. |
Important: the heartworm antigen test detects Dirofilaria immitis. It does not detect the subcutaneous worm (D. repens), which is also common in Central Europe; for that you need a Knott test or PCR. This matters because, according to the European ESCCAP guideline, D. repens causes most human infections in Europe.
When should you do a heartworm test?
According to the ESCCAP (European Scientific Counsel Companion Animal Parasites) guideline, antigen from adult female worms appears in the blood about 6–8 months after infection. A recent infection therefore does not yet show up on the test, and timing matters at least as much as the test itself.
| Situation | When to test? |
|---|---|
| Yearly routine screening | In spring, before mosquito season and preventive treatment begin. By then, infections from the previous season can be detected. |
| No prevention this year | In autumn or winter: by then an infection picked up early in the season can be detected. If negative, repeat in spring, because bites from late summer only become visible by then. |
| Before starting preventive treatment | Always. If the dog is already infected, starting prevention must be agreed with a vet. |
| A missed or late dose | About 6–7 months after the missed dose. |
| New dog, adoption, dog brought from abroad | On arrival, then again after about 6 months, because a recent infection does not yet show on the first test. |
| Persistent cough, tiring easily, difficulty breathing | Immediately – and in this case always take your dog to the vet as well. |
Yearly screening is also recommended for dogs on preventive treatment. A forgotten tablet, a spot-on that was washed off or a late dose is enough for protection to lapse.
How does a heartworm test work at home?
The MancsLab HW Ag rapid test works with a fresh blood, serum or plasma sample from dogs and cats. According to the instructions for use, the steps are:
- Preparation: the test can be done at 15–30 °C. Unpack the cassette and place it on a clean, flat surface.
- Sampling: a drop of blood can be taken by a tiny prick at the edge of the ear with a sterile lancet, as is usual for blood glucose testing in diabetic pets. The lancet is not included in the pack. If you would rather not do this yourself, ask your vet to take a blood sample.
- Mixing: using the dropper provided, put 3 drops of sample into the buffer vial, close it and shake.
- Applying: put 3 drops of the mixed sample into the sample well marked S on the cassette.
- Reading: read the result between 5 and 10 minutes. After 15 minutes the test can no longer be interpreted.
According to the manufacturer's validation, the test has a sensitivity of 96.00%, a specificity of 98.33% and 97.40% agreement with the reference method. We explain what these numbers mean in practice here: How accurate is a home rapid test?
How do you interpret the result?
| Result | What you see | What to do |
|---|---|---|
| Positive | Both C and T lines appear, even a faint T line | See a vet. They will confirm the result and assess how severe the infection is. Until then, avoid strenuous exercise for your dog. |
| Negative | Only the C (control) line is visible | No detectable antigen in the sample. However, the test cannot yet see an infection from the past 6–8 months, so stick to the scheduled repeat test. |
| Invalid | No C line | Repeat with a new cassette and a new sample. |
A negative result can occur in an infected animal for several reasons: the infection is very recent, there are few worms, or only male worms are present (the test does not detect their antigen). If you see symptoms, see a vet even after a negative home test.
What does a heartworm test cost in 2026?
As an example, here are public 2026 price lists from a few Hungarian clinics. Prices in your country may differ considerably:
| Where? | What is included? | Price |
|---|---|---|
| Budapest clinic (District XI) | Heartworm rapid test + microscopic blood smear; examination fee charged separately | HUF 10,000 |
| Budapest clinic (District III) | In-clinic rapid test; general examination HUF 16,500 | HUF 11,500 |
| Clinic in Pest county | Heartworm screening | HUF 16,000 |
| Clinic in Pécs | Heartworm and subcutaneous worm: ELISA + Knott test; examination HUF 14,500 | HUF 18,000 |
| MancsLab home rapid test | HW Ag antigen rapid test for dogs and cats | See the product page for the current price; better value in a 5-pack |
A clinic price often includes more than a rapid test: an examination, a microscopic or Knott test, and a vet on hand. A home test makes routine yearly pre-screening cheaper and more convenient. This matters especially if you have several dogs or run a kennel. With a positive result, however, a veterinary examination cannot be skipped.
Heartworm testing in cats
Cats can also be infected with heartworm. According to ESCCAP, infection rates in cats are generally only a tenth of those in dogs, but the course of the disease in cats is often less predictable. The antigen test is also very specific in cats, so a positive result is strong evidence of infection. A negative result, however, can easily occur in an infected cat too, because cats often harbour only a few worms, or only male worms. In cats, therefore, a negative test does not rule out infection. With symptoms (coughing, asthma-like breathing, recurring vomiting), your vet may also recommend an X-ray, cardiac ultrasound and an antibody test.
What should you do if the result is positive?
- Don't panic, but don't put it off either. Book an appointment with your vet and bring the cassette or a photo of the result.
- Restrict exercise. Strenuous running and ball games increase the load on the heart and pulmonary vessels.
- Don't start giving a preventive product on your own. In an infected dog, your vet will plan the order and timing of treatment.
- Check your other animals too. Heartworm does not spread directly from animal to animal, but the same mosquitoes may have bitten them. It is worth screening the other dogs in the household as well.
Frequently asked questions about heartworm testing
When should my dog have a heartworm test?
Once a year, ideally in spring, before mosquito season and preventive treatment. If your dog has not received prevention, it is also worth screening after the season and repeating in spring. For a new dog, testing on arrival and again 6 months later is recommended.
How long after infection does the test detect it?
According to ESCCAP, antigen from adult female worms appears about 6–8 months after infection. Before that, the test can be negative even if the dog is already infected.
How much does a heartworm test cost?
It depends on the country and the clinic. In Hungary, for example, public 2026 price lists show in-clinic heartworm screening at HUF 10,000–18,000, often plus a separate examination fee. You can find the current price of the MancsLab HW Ag home rapid test on the product page; the 5-pack is better value.
Does the test also detect the subcutaneous worm?
No. The antigen rapid test detects heartworm (Dirofilaria immitis). For the subcutaneous worm (D. repens) you need a Knott test or PCR.
Does my dog need a heartworm test if it receives preventive treatment?
Yes, once a year is recommended. A missed or late dose can leave a gap in protection, and only screening can reveal this.
Can the home test be used for cats too?
Yes, the HW Ag test can be used with samples from both dogs and cats. In cats a positive result is a reliable sign, but a negative result does not rule out infection, so symptoms call for a veterinary work-up.
How do I take blood at home?
With a tiny prick at the edge of the ear using a sterile lancet, as is usual for blood glucose testing. The test pack includes a dropper but not a lancet. If you are unsure, ask your vet to take a blood sample; you can then do the test at home with the sample.
Summary
Heartworm is no longer rare in Central Europe: in Hungary roughly one in six dogs living without prevention is infected. The disease is symptom-free for a long time, and infection can only be detected after 6–8 months. That is why a single, well-timed yearly screen is worth the most – ideally in spring, and after the season too if there was no prevention. With a positive result, the next step is up to your vet.
HW Ag heartworm rapid test for dogs and cats →
Home screening with a result in 5–10 minutes. Also available in a 5-pack for several dogs.
Sources
- New Insights into the Prevalence of Dirofilaria immitis in Hungary. Animals, 2025, 15(9):1198. PMC12071041
- ESCCAP Guideline 05: Control of Vector-Borne Diseases in Dogs and Cats (2024). esccap.org
- Public Hungarian veterinary price lists (2026): EteleVet, Állati Doktorok, Ligeti Állatorvosi Rendelő, Állatorvos Pécs
- MancsLab HW Ag instructions for use (with manufacturer's validation data)
Important: this article provides general information and does not replace veterinary advice. MancsLab rapid tests are intended for preliminary screening at home; the diagnosis is made by a vet.