Retrospective study of rabies epidemiology in Ukraine (1950-2019)

During many decades, rabies remained endemic on the territory of Ukraine. In certain historical periods, the epizootic process of rabies developed with the alternate inclusion of different species of animals as a source and a reservoir of the virus which are of great interest to many scientists. Therefore, the purpose of our study was to conduct an analysis of rabies epidemiology on the territory of Ukraine from 1950 to 2019 based on collected reliable archival data. Collected archival data have shown that over the past 70 years sources of rabies infection varied from domestic to wild carnivorous and vice versa with three major epizootic peaks. The first and the highest peak in the entire study period was recorded in 1951 (3 724 cases) and was caused by the spread of the rabies virus solely through dogs. The second peak with lower number of cases was recorded in 1979 (1 594 cases) when the dominant role in the spread of rabies virus turned to foxes. Finally, the third peak in 2007 (2 932 cases) was triggered by the combination of animals (foxes, dogs, and cats) as the source of the pathogen. Considering significant peaks and downturns and the varying degrees of involvement of domestic and wild animals in spreading of the pathogen, we have identified five historically important stages in the development of the epizootic process: the stage of «urban» or «dog» rabies (1950–1959), relative stability (1960–1969), «sylvatic» or «fox» rabies (1970–1990), relative safety (1991–1999), and expansion (2000–2019). At the stage of «urban» rabies dogs played a significant role as a source and a reservoir of the virus. In the epizootic aspect, dogs made up 54.3 % of all rabies cases, while cats and wild animals (wolves, raccoon dogs, foxes, raccoons, martens, and lynxes) – 1.58 % and only 0.05 % respectively. Domestic animals (cattle, pigs, horses, goats, etc.) made up the rest 44.07 %, but they were «victims» and did not contribute to the further spread of the virus. Moreover, in 89 % of cases dogs were a source of rabies for humans. The stage of «relative stability» was marked by decline of epizootics throughout Ukraine and decrease in the number of deaths to 140 per year. «Sylvatic» or «fox» rabies stage was characterized by the involvement in the epizootic process of a new species of animals – the red fox (Vulpes vulpes). During this stage the proportion of wild animals in the total number of cases was 33.9 %, cats – 17.7 %, and dogs – 12 %. In 46.5 % of cases foxes were the main source of rabies for humans, while cats and dogs in 34.2 % and 11.8 % of cases respectively. The stage of «relative safety» was marked by the repeated prolonged decline of epizootics and the increasing role of dogs and cats in the epizootic process. The last stage of the expansion took place against the background of the increasing population size and proportion of rabies cases among domestic carnivores (up to 44.6 %) and foxes (up to 36.5 %), which contributed to the widest distribution of the virus, and remains a significant problem nowadays. While in the period of «urban rabies» vaccination of dogs together with the regulation of their population allowed to reduce the number of rabies cases by 26 times in 15 years, nowadays regulation of fox and domestic carnivores populations in combination with oral vaccination of wild and parenteral vaccination of companion animals, unfortunately, do not give visible result. So, it is extremely important not only to increase the quality of preventive measures against rabies, but also to increase their quantity in order to cover all three major sources of rabies – dogs, cats, and foxes