Although heartworm disease has been part of public awareness in Hungary for more than five years, there are still many misconceptions and misunderstandings surrounding “heartworms” and their prevention.
“I only have to think back to one of my recent on-call shifts, where I diagnosed four heartworm-positive dogs. Two of the owners had no idea about the real danger, while the other two believed they were protecting their dogs against it—unfortunately, incorrectly…”
— Dr. Antal Rengei
This parasite, which previously occurred mainly in southern, Mediterranean regions, has now found ideal living conditions in our country as well. In infected animals, it can cause severe health damage and, in serious cases, even death. Moreover, it is a zoonotic disease, meaning it can pose a risk to humans as well.
For this reason, it is crucial to understand how heartworm infection can be prevented, detected, treated, and what to watch out for in order to protect the health of our dogs and cats.
How Does Infection Occur?
The “baby worms” of heartworms and skin worms—called microfilariae—are transmitted by mosquito bites from one animal to another after a short incubation period. The larvae ingested by mosquitoes develop further when the environmental temperature exceeds 14 °C, molting twice within the mosquito over a period of 2–3 weeks. During the next blood meal, these larvae are transmitted to a new host—animal or human.
These L3 larvae undergo several molts while migrating within the new host’s body. Skin worm larvae may reach the brain, lungs, abdominal cavity, eyes, while heartworm larvae migrate to the heart and their primary habitat, the pulmonary arteries, where they cause damage and eventually mature and reproduce.
Humans are fortunately a dead-end host for heartworms, so infections usually result in milder issues rather than full disease development.
Diagnosis and Differentiation
If heartworm infection is suspected—meaning microfilariae are detected in the blood—it is essential to determine whether skin worm or heartworm larvae are present, as treatment protocols differ significantly.
For this purpose, reliable rapid tests and PCR diagnostics are available.
In both cases, it is critical to eliminate microfilariae with careful and appropriate treatment, ensuring that the infected dog no longer poses a risk to its environment. In cooperation with the owner, an optimal strategy must also be chosen to eliminate adult worms from the body.
Prevention Is the Most Important Step
Because adult heartworms take 6–8 months to develop after a mosquito bite, prevention strategies differ between young puppies and adult animals.
Puppies
A puppy that tests negative can remain negative for life if continuous monthly preventive treatment is started early—from 6–8 weeks of age onward. These treatments protect both against mosquitoes and microfilariae (heartworm and skin worm larvae). Effective prevention is available in the form of spot-on solutions and tablets, obtainable through veterinary clinics.
Adult Animals
After 6–7 months of age, before starting preventive treatment, it is essential to determine whether the dog or cat is already infected. Using inappropriate products or incorrect dosing may contribute to drug-resistant heartworm strains and may even endanger the animal’s life.
Therefore, preventive treatment must only be started after proper veterinary examination and with precise dosing.
Screening Examinations
Detecting heartworm and skin worm infection is essential for ensuring the safety of both pets and their families.
Procedure:
Blood samples are taken from the dog or cat. Microfilariae are searched for under a microscope, and rapid tests are performed on-site to detect adult female heartworms. Together, these methods identify infection with approximately 90% accuracy.
More advanced laboratory tests (PCR diagnostics and expert parasitological evaluation) allow for even more precise identification of the parasite type, which is particularly important before eliminating adult worms.
If heartworm disease is suspected, chest X-rays and cardiac ultrasound, in addition to physical examination, are essential to assess the severity and progression of the disease.
Treatment
If tests confirm infection, treatment must be carried out with extreme caution.
First, microfilariae must be eliminated, followed by treatment targeting adult heartworms. Killing adult worms places a significant burden on the animal, as dead worms may lodge in smaller pulmonary arteries, causing embolisms that can be fatal.
Such treatment must only be initiated under strict veterinary supervision, with rigorous activity restriction and adherence to professional protocols.
If the Animal Tests Negative
If screening results are negative, owners may feel some relief—but continued protection and regular monitoring are essential for life.
Screening should be repeated after six months, then annually, to confirm the effectiveness of prevention.
When regular testing is combined with monthly preventive treatment and mosquito control, pets and families can be kept safe.
Final Advice
Always consult your veterinarian when developing a prevention or treatment protocol, as many factors must be considered when selecting products and determining dosages.
At Kisállat-Ambulancia, we are happy to assist you in every step—please contact us with confidence.
