New Insights Into a Growing Threat to Hungarian Dogs
A silent threat is spreading through Hungary, carried by the humble mosquito.
Heartworm disease, caused by the parasitic worm Dirofilaria immitis, is an emerging mosquito-borne disease with potentially fatal outcomes for dogs. Once confined to Mediterranean regions, it has been steadily spreading into Central and Eastern Europe. A groundbreaking new study reveals that the situation in Hungary is more pressing than ever, with infection rates climbing to alarming new levels 1 5 .
Heartworm disease is a zoonotic condition, meaning it can be transmitted from animals to humans. The parasite's life cycle is a complex journey between two hosts 2 7 :
An infected mosquito bites a dog, depositing immature larvae (L3) onto the skin, which then penetrate the wound. Over about 6 to 7 months, these larvae mature into adult worms that reside in the pulmonary arteries and right ventricle of the heart. Adult females release early larval stages, known as microfilariae, into the bloodstream 2 7 .
When a mosquito takes a blood meal from an infected dog, it ingests these microfilariae. Inside the mosquito, the microfilariae develop into the infective L3 stage. The mosquito then transmits these larvae to a new dog during its next blood meal, continuing the cycle 2 .
Infected mosquito transmits L3 larvae to dog
Larvae mature into adult worms in 6-7 months
Adult females release microfilariae into bloodstream
Mosquito ingests microfilariae during blood meal
For decades, heartworm disease was a problem primarily for dogs in Southern Europe. However, over the last 20 years, the parasite has significantly expanded its range 5 . The first homegrown (autochthonous) case of D. immitis in a dog in Hungary was reported only in 2009 1 . Subsequent studies have shown a worrying trend: the prevalence jumped from an average of 2.7% between 2011 and 2015 to 11.3% by 2017 6 . The latest research confirms that this expansion is not slowing down.
A team of researchers from the University of Veterinary Medicine Budapest set out to determine the current scale of the problem. Their study, published in 2025, provides the most up-to-date picture of heartworm prevalence in Hungary 1 3 .
Between March 2023 and February 2024, the researchers collected 1,071 blood samples from client-owned dogs across all 19 counties of Hungary 1 . To ensure an accurate picture of local transmission, the study included only dogs born in Hungary that had never left the country and had not received heartworm prevention medication in the past year 1 .
Each sample was rigorously tested using three different methods:
The countrywide analysis revealed a prevalence of 17.0% 1 9 . This finding indicates a continuous and significant increase from the 11.3% prevalence reported just a few years prior, confirming that the parasite's spread is accelerating across the country 1 .
| Study Period | Reported Prevalence | Key Change |
|---|---|---|
| 2011-2015 | ~2.7% | Baseline |
| 2017 | 11.3% | Significant Increase |
| 2023-2024 | 17.0% | Continuous Increase |
Older dogs are at higher risk. The study found significantly higher infection rates in dogs aged 5-10 years and those over 10 years old compared to younger dogs 6 . This is likely simply due to having more years of exposure to infected mosquitoes.
A dog's lifestyle plays a crucial role. Dogs kept exclusively outdoors had a dramatically higher infection rate, with over half testing positive in one community science study. Dogs with a "mixed" indoor-outdoor lifestyle also had a higher risk compared to those living strictly indoors 6 8 .
| Lifestyle | Relative Risk | Key Insight |
|---|---|---|
| Outdoor | Very High | Highest exposure to mosquito bites. |
| Mixed (Indoor/Outdoor) | High | Regular exposure during outdoor time. |
| Indoor | Lower | Reduced, but not zero, risk. |
The heartworm story isn't just about dogs. Its expansion is a classic "One Health" issue, illustrating the interconnectedness of animal, human, and environmental health.
Multiple mosquito species common in Hungary can transmit the parasite, including Aedes vexans, Aedes koreicus, and Culex pipiens 5 6 . Climate change is a key driver of the disease's spread. Rising temperatures extend the breeding season and geographic range of these mosquitoes and also accelerate the development of the parasite within them, creating a longer annual window of transmission 1 5 .
Warmer Temperatures
Expanded Range
Longer Season
While humans are "dead-end hosts" where the parasite cannot complete its life cycle, infection can still occur. When an infected mosquito bites a person, the immature worm can migrate to the lung, die, and cause a pulmonary nodule. This lesion often looks like a potential lung cancer on a radiograph, leading to unnecessary surgery and significant distress for the patient 2 . A 2024 case series from Hungary documented five such human pulmonary dirofilariasis cases over a 12-year period, all confirmed by PCR after surgical removal of the lung nodules .
Understanding the tools scientists use to diagnose and study heartworm helps appreciate the rigor behind these findings.
| Tool / Reagent | Function in Research |
|---|---|
| EDTA Blood Tubes | Prevents blood coagulation for microfilaria and DNA analysis. |
| Serum Tubes | Allows collection of blood serum for antigen testing. |
| DiroCHEK® ELISA Kit | Detects specific antigens from adult female heartworms. |
| DNeasy Blood & Tissue Kit | Extracts pure DNA from blood samples for molecular analysis. |
| Real-time PCR Primers/Probes | Targets and amplifies specific Dirofilaria DNA sequences for sensitive detection. |
| Knott's Test (2% Formalin) | Concentrates microfilariae for visual identification under a microscope. |
The evidence is clear: heartworm is a growing and established threat to dogs in Hungary. The rise to 17% prevalence is a call to action for veterinarians and dog owners alike 1 . Fortunately, this serious disease is largely preventable.
The most effective strategy is year-round preventive medication, typically given monthly as a chewable tablet or a spot-on treatment. These medications are highly effective and belong to the macrocyclic lactone drug class, which includes ivermectin and moxidectin 7 .
Dog owners throughout Hungary, particularly in high-prevalence regions and for dogs with outdoor access, are strongly encouraged to consult their veterinarian about starting a prevention protocol. In the face of this expanding threat, proactive prevention is the best defense.
Consult with your veterinarian to establish a heartworm prevention plan tailored to your dog's specific needs and risk factors.