Rapid spread and emergence of heartworm resulting from climate and climate-driven ecological changes in Hungary.

In Europe, Dirofilaria immitis persists mainly in the southern countries with a Mediterranean climate. Because spreading of heartworms from these countries towards the northern ones could be observed in the past decades, necropsy records of 4076 Hungarian dogs were reviewed for heartworm infections. The first autochthonous canine D. immitis case was detected on the Great Hungarian Plain in 2007. Until 2011, the number of heartworm infection cases was low, and these cases were restricted to a small part of the Great Hungarian Plain. Since 2012, the number of cases has increased considerably, and the rapid expansion of the parasite's geographic range could also be observed. Our retrospective study has revealed that most of the Hungarian territory became a heartworm endemic region, and the prevalence of infection greatly multiplied over the past 12 years. The establishment, rapid spread, and emergence of D. immitis may be mainly explained by the warming climate in Hungary. However, the partly climate-driven spread of the most important reservoir host in wildlife, the golden jackal (Canis aureus) from the Mediterranean Balkan Peninsula might have also played a significant role. This study is an example of the rapid spread and emergence of pathogens resulting from climate and climate-driven ecological changes. Because a continuous increase in the temperature and further dispersal of golden jackals in Europe are projected, further spread and emergence of heartworm can be expected. Similar spread and emergence of D. immitis could be observed in North America. It cannot be excluded that similar reasons (global warming and rapid dispersal and population growth of the most important wild canine reservoir host) are in the background on both continents.