The range of Dirofilaria repens Railliet & Henry, 1911 in central and northwestern Russia

The purpose of the research is to assess the current distribution of the nematode Dirofilaria repens in the Northwestern (NWFD) and Central (CFD) Federal Districts of Russia using molecular genetic methods.Materials and methods. A single-center retrospective study was conducted. A total of 4,431 whole blood samples from dogs collected in various locations were analyzed using a species-specific polymerase chain reaction (PCR).Results and discussion. D. repens DNA was detected in 7.69% (341/4,431) of the analyzed samples. The parasite was detected in 19 of the 26 regions studied. The PCR confirmed D. repens for the first time in 13 regions of the Russian Federation that were not previously considered endemic, including the Arkhangelsk, Kaliningrad, Pskov, Novgorod, Tambov, Lipetsk, Yaroslavl, Tver, Bryansk, Ivanovo, Kaluga, Ryazan, and Tula Regions. The highest infection prevalence (IP) was recorded in the Ivanovo Region (63.9 ), the Kursk Region (50.0%), and the Pskov Region (46.7%). Previously known endemic foci such as the Belgorod Region (IP = 18.6%) and the Voronezh Region (IP = 17.1%) also showed positive results. The obtained data indicate a significant expansion of the D. repens range in northern and northwestern directions across European Russia. A significant limitation of the study was the inability to completely rule out cases of imported infection due to the lack of data on animal displacements. Furthermore, targeted sampling from animals clinically suspected of having dirofilariasis may have led to an overestimation of prevalence estimates. Nevertheless, the high proportion of positive samples in regions with representative sampling clearly indicates active local pathogen transmission in most of the studied areas.