Recent research reveals an alarming escalation in heartworm prevalence, with infection rates climbing to 17.0% in 2024 1
For decades, heartworm disease remained a distant concern for Hungarian dog owners—a problem confined to Mediterranean vacation destinations rather than the plains of Central Europe. That reality has fundamentally changed. Recent research reveals an alarming escalation in the prevalence of Dirofilaria immitis, the parasitic worm responsible for this potentially fatal disease 1 . What was once an imported curiosity has become an established local threat, with infection rates climbing steadily across the country. This silent epidemic stems from a combination of climate change, increased animal movement, and evolving mosquito populations that have collectively transformed Hungary's disease landscape 1 .
The numbers tell a concerning story. A comprehensive countrywide screening conducted between 2023 and 2024 found that 17.0% of dogs tested positive for D. immitis infection—a significant increase from the 11.3% prevalence reported just years earlier 1 . This dramatic jump confirms that heartworm is not merely present in Hungary but is actively spreading, creating new risks for pets and their owners alike. Understanding this emerging threat has become essential for veterinarians and dog owners across Central Europe.
Rapid increase in heartworm prevalence since first detection in Hungary.
Heartworm disease is caused by Dirofilaria immitis, a parasitic nematode that represents one of the most dangerous mosquito-borne parasites affecting carnivores worldwide 1 . These slender, thread-like worms have a complex lifecycle that involves both mosquito vectors and mammalian hosts, primarily targeting dogs but capable of infecting other species including humans.
While dogs are the primary host, humans can accidentally become infected through mosquito bites, though we are considered "dead-end hosts" 1 . In humans, the parasites typically remain in immature form without producing microfilariae, often causing respiratory symptoms when they become trapped in lung tissue 1 . This zoonotic dimension adds public health significance to what is primarily a veterinary concern.
The heartworm transmission cycle begins when a mosquito bites an infected animal and ingests microscopic baby worms known as microfilariae circulating in the bloodstream.
Within the mosquito, these microfilariae develop into infective larvae over approximately two weeks, influenced by environmental temperatures 1 .
When that mosquito subsequently bites another dog, it deposits these larvae onto the skin, where they enter through the bite wound and begin their migration.
Once inside a dog, the larvae undergo several developmental stages over approximately six months, gradually migrating to the heart and pulmonary arteries where they mature into adults that can reach lengths of up to 30 centimeters 1 .
These adult worms then mate and release new microfilariae into the bloodstream, continuing the transmission cycle when another mosquito feeds on the infected dog.
Between March 2023 and February 2024, a team of researchers from the University of Veterinary Medicine Budapest embarked on an ambitious countrywide study to assess the current status of heartworm in Hungary 1 . Their research involved collecting 1,071 blood samples from domestic dogs across all 19 Hungarian counties, with sample numbers proportional to the local dog population in each region 1 .
The study employed strict inclusion criteria to ensure accurate assessment of local transmission. Researchers only included dogs that were born in Hungary and had never left the country, and excluded any animals that had received heartworm prevention medication in the past year 1 . This careful approach guaranteed that detected infections were truly autochthonous (locally acquired), providing a clear picture of the parasite's establishment in Hungary.
The research team utilized multiple diagnostic techniques to ensure comprehensive detection of D. immitis infections:
This multi-method approach provided overlapping layers of detection sensitivity, ensuring that infections wouldn't be missed due to the limitations of any single diagnostic technique.
The study results confirmed researchers' concerns about the accelerating spread of heartworm disease. The countrywide prevalence of 17.0% marks a substantial increase from previous measurements, demonstrating a continuous upward trend in infection rates 1 . This represents a 50% increase from the 11.3% prevalence reported in earlier studies, indicating that the parasite is rapidly establishing itself across Hungary 1 .
The historical context underscores the dramatic nature of this increase. The first autochthonous case of D. immitis in Hungarian dogs was only reported in 2009 1 . Subsequent studies documented a gradual rise from 0.0% to 2.7% between 2001-2015, followed by a jump to 11.3% by 2017, and now to the current 17.0% 1 . This progression illustrates an emerging disease establishing itself with increasing velocity.
The comprehensive data analysis identified specific factors that significantly influence a dog's likelihood of infection:
| Risk Factor | Effect on Infection Risk | Explanation |
|---|---|---|
| Age | Significantly higher in older dogs | Longer exposure time to mosquito bites 4 |
| Living Conditions | Higher in outdoor dogs | Increased exposure to mosquito vectors 4 |
| Geographical Location | Highest in southeastern and eastern regions | Favorable mosquito habitat conditions 4 |
The research confirmed that older dogs face substantially higher infection rates, with animals aged 5-10 years and over 10 years showing significantly higher prevalence 4 . This pattern reflects the cumulative nature of exposure risk—the longer a dog lives in an endemic area, the greater its probability of eventually being infected.
Similarly, dogs kept exclusively outdoors demonstrated higher infection rates compared to those with indoor access, underscoring the role of exposure to mosquito habitats 4 .
The geographical analysis revealed uneven distribution across Hungary, with the highest prevalence observed in the southeastern (47.8%) and eastern regions (43.4%) 4 . This pattern suggests that local environmental conditions—possibly including temperature, humidity, and mosquito population density—create hotspots for transmission.
The accurate detection and study of D. immitis requires specialized laboratory techniques and reagents. The Hungarian research team employed a comprehensive approach to ensure their findings' reliability.
| Tool/Reagent | Function | Application in Study |
|---|---|---|
| EDTA Tubes | Prevents blood coagulation | Blood sample collection for Knott's test and PCR |
| Serum Tubes | Allows blood to clot for serum separation | Sample collection for ELISA testing |
| DiroCHEK® Kit | Detects adult worm antigens | ELISA testing for current infections |
| DNeasy Blood & Tissue Kit | Extracts and purifies DNA from samples | Preparation for molecular analysis |
| Real-time PCR Master Mix | Enables DNA amplification | Detection and species differentiation |
| Formalin (2%) | Preserves and fixes microfilariae | Preparation for Knott's test microscopy |
| Methylene Blue (0.1%) | Stains microorganisms for visibility | Visualization of microfilariae in Knott's test |
Each diagnostic technique offers distinct advantages in heartworm detection:
This multi-method approach is particularly valuable for understanding true disease prevalence, as each technique compensates for the limitations of the others, providing a comprehensive picture of infection rates.
The steady increase in heartworm prevalence underscores the critical importance of preventive measures for dogs in affected regions 1 . Preventive medications—typically administered monthly as chewable tablets or topical solutions—work by eliminating the immature larval stages before they develop into adult worms. The Hungarian researchers specifically noted that the dogs in their study had not received preventive treatment in the past year, highlighting how preventable these infections truly are 1 .
The expansion of heartworm in Hungary reflects broader patterns of change in disease distribution across Europe. Historically confined to Mediterranean regions, D. immitis has progressively moved northward into Central and Eastern Europe 1 . Climate change represents a significant driver of this expansion, as rising temperatures extend the breeding season of mosquitoes and accelerate parasite development within vectors 1 .
Research indicates that the summer temperature of the Great Hungarian Plain—already the warmest region in the country—has shown marked increases in recent decades . These changing climatic conditions create increasingly favorable environments for both mosquito vectors and the development of D. immitis larvae within them.
Complementary research conducted in Hungary has demonstrated the value of combining multiple monitoring strategies. A 2025 study published in Parasites & Vectors successfully integrated community science with molecular xenomonitoring—testing mosquitoes for infection—to track disease distribution 4 . This approach revealed D. immitis infection in multiple mosquito species, including Aedes albopictus, Aedes koreicus, and Aedes vexans, with the highest infection rates observed in the same southeastern and eastern regions where dog infections were most prevalent 4 .
The dramatic rise in heartworm prevalence in Hungary—from zero cases before 2006 to 17.0% in 2024—serves as a striking case study in how quickly disease landscapes can change 1 . This emerging threat to dog health underscores the interconnectedness of climate change, wildlife populations, and companion animal health.
For Hungarian dog owners, these findings highlight the importance of regular veterinary testing and consistent preventive medication, particularly for older animals and those spending significant time outdoors. For the broader scientific community, the Hungarian experience offers valuable insights into how parasites can establish themselves in new territories, providing lessons that may help other regions prepare for similar emerging disease threats.
As climate patterns continue to evolve and animal movement increases, the story of heartworm in Hungary may represent just one chapter in a larger narrative of changing disease distributions across Europe and beyond. Vigilance, prevention, and continued research remain our most powerful tools in protecting both animal and human health from these emerging challenges.