Dirofilariasis, known as “heartworm“, is no longer an exotic disease for Bulgaria. The parasite is transmitted through the bite of an infected mosquito and can remain unnoticed for a long time, while it gradually damages the animal's heart and lungs. Dr. Ranko Georgiev, a doctor at the Central Veterinary Clinic Sofia, speaks to FACT.
- Dr. Georgiev, in recent years, there has been more and more talk about heartworm in dogs. Is the disease really becoming a serious problem in Bulgaria as well?
- If we look back – Only 15 years ago, for us - as doctors, Dirofilariasis was an exotic disease that we rarely encountered. Mostly in patients who traveled to Greece or southern Italy. Unfortunately, today there are so many cases that for us it has become a trivial, almost mandatory diagnosis in dogs with compromised deworming. According to a study conducted in Bulgaria a few years ago, more than 40% of the population of stray dogs carries the disease (and serves as a reservoir host), as well as almost 100% of the population of wolves and jackals.
- What is dirofilariasis and how does the parasite reach the heart and pulmonary vessels of the animal?
- This is a parasitic disease (roundworm from the family of worms) that affects the lungs and heart. The parasites are transmitted through an intermediate host (mosquito), which transmits the larvae to the final host (the dog) when bitten. A period of about 8 months follows until the parasites reach the heart, where they begin to multiply, releasing the so-called microfilariae - babies, which are taken in when feeding by the next mosquito, which completes the cycle. If we transfuse blood from an infected animal to a healthy animal, the disease does not occur. At least 20 days are needed for the larvae to live in the mosquito's body to become capable of infecting.
- What are the first symptoms that should prompt owners to seek veterinary care immediately, and why does the disease often go unnoticed in its early stages?
- In many parasitic diseases, there are long periods in which there are no clinical symptoms. Even seriously infested dogs do not show any signs for owners to register for years. This makes the disease particularly dangerous, because when symptoms appear - bloating (ascites), coughing, weight loss, refusal to move - the disease is usually already in its final stage, with high risk for the patient. The good news is that there are quick and accurate blood tests on the market, which we - as doctors, recommend for any patient with an unclear history for proper deworming. They help us to detect patients with the disease but without symptoms and to make timely additional diagnostics (usually chest X-ray and echocardiography).
- In addition to dogs, can cats also become infected with heartworm and how does the course of the disease differ in the two species?
- We almost never see cats with this disease. The parasite is very narrowly specialized for canids (dogs, jackals, wolves). Although cats, and also humans, are bitten by infected mosquitoes, the disease does not occur. The cat's immune system destroys the larvae and they do not reach the heart. It is possible, although very rare, for cats to develop Dirofilariasis. However, the disease in them runs a hidden course, in most cases asymptomatic. With clinical tests and echocardiography we can prove the disease, and cats usually cough as symptoms.
- To what extent do climate change and the increase in the mosquito population affect the spread of heartworm disease in Bulgaria?
- The influence of climate change is decisive for the spread of the disease. If there are not at least 20 warm days (with an average temperature above certain degrees), the development cycle of the parasite cannot be closed. The larvae die in the mosquito's body and there is no infection. Climate change is the direct reason why we see cases of heartworm disease in Bulgaria, and now even in the southern part of Romania. In northern Europe, there are still no registered cases for patients who have not traveled south.
- Does modern veterinary medicine have sufficiently effective methods for diagnosis and treatment, or does prevention remain the strongest weapon against the disease?
- Prevention is definitely the best way to limit the disease. There are a number of preparations on the market that, when applied correctly, provide practically one hundred percent protection. They are applied every month after consultation with the veterinarian who knows the patient.
We also have reliable diagnostic methods - serological tests that detect the presence of adult forms in the host, as well as ultrasound protocols for assessing and classifying the extent of the disease. We often detect the disease by chance - during combined tests for other vector-borne (mainly tick-borne) diseases.
- What preventive measures would you recommend to dog and cat owners - when should prophylaxis begin and is it necessary to carry it out year-round?
- For a country like Bulgaria, our recommendation is that heartworm prophylaxis be monthly - 12 months a year. Although the risk during the winter months is much lower, a number of studies have shown that in large cities there are so-called warm pockets in which mosquitoes remain alive year-round. Even just one bite from a mosquito carrying the parasite is enough for a dog to become infected. The parasite is extremely well adapted to this host and after a bite there is practically 100% infection. Prevention BEFORE the bite is the only way to definitely protect your pet.
Ask your veterinarian which of the many products on the market is suitable specifically for your pet.
- Have you observed an increase in cases of heartworm disease in recent years and what would you say to people who think that their pet "cannot possibly get infected" because it lives mainly in an urban environment?
- The good news is that to date, cases are decreasing – mainly due to the increasing awareness of owners about prevention. However, we see cases of Dirofilariasis every day and in some of the patients the degree of the disease is high, requiring even surgical removal of some of the parasites.
Unfortunately, there is no sure protection if you rely only on repellents or living indoors. There are mosquitoes even on the highest floors of apartment buildings in cities and although the risk of biting a furry pet is lower, it does exist. In our daily practice, we see a variety of dogs sick with heartworms - from Chihuahuas to Irish Wolfhounds, and the risk exists for everyone.
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Dr. Ranko Georgiev
He graduated from the National Natural Sciences and Mathematics High School with a Biology major, and later from the Thracian University in Stara Zagora with a degree in Veterinary Medicine (graduation 1999).
He had internships and specializations in the USA, Spain, Germany, the Czech Republic, Greece and a number of others - with a focus on Cardiology, soft tissue surgery, internal medicine, imaging diagnostics. The most interesting of which are at Colorado Teaching Hospital under the leadership of Dr Chris Orton and June Boon, and at the University of Davis – California with Dr Mark Kittleson. Since 2017 – he specializes in Cardiology at ESAVS – Master in Veterinary Cardiology, University of Luxembourg.
Some of the professional organizations of which he is a member:
ESVC - European Association of Veterinary Cardiology; www.esvc.com ACVR – American College of Radiology; IVUSS section – International Association for Ultrasound in Veterinary Medicine; www.acvr.com EAVDI – European Association for Diagnostic Imaging; www.eavdi.com VIN – The largest international forum for veterinary medicine; www.vin.com BAVK – Bulgarian Association of Veterinary Cardiology, where he is one of the founders and current Manager; www.bavc.bg
Dr. Georgiev's main clinical interest is in the field of Invasive Radiology - interventional procedures under fluoroscopic control: pacemaker implantation, removal of heartworms from the heart, valvuloplasty in pulmonary stenosis, placement of occluders in congenital heart defects and a number of others. Most of these techniques were performed for the first time in Bulgaria by him.