Distribution of Dirofilaria repens (Railliet et Henry, 1911) in Southern and Southeastern Russia

The aim of the study was to investigate the current distribution of Dirofilaria repens in dogs from the Southern, Volga, and North Caucasian federal districts of European Russia. A total of 6,444 canine blood samples from 100 localities were screened using a species-specific real-time PCR assay. D. repens DNA was detected in 485 samples (7.52% prevalence), confirming the parasite's presence across a vast area. Positive cases were identified in the Republics of Bashkortostan, Mari El, Mordovia, Tatarstan, Chuvashia, Karachay-Cherkessia, Chechnya, Adygea, and the Crimean Peninsula, as well as in Perm, Stavropol, Krasnodar, Rostov, Volgograd, Astrakhan, Ulyanovsk, Samara, Penza, Nizhny Novgorod, and Kirov regions. The prevalence varied significantly among regions, ranging from 1.04% in Astrakhan region to 48.39% in the Republic of Mari El. While the lack of travel histories for sampled dogs means that some detected cases could be imported, the high prevalence observed in many cities provides robust evidence of autochthonous transmission. Our findings demonstrate that D. repens is now endemic across a much broader territory of European Russia than previously recognized, including lesser-known foci in the Volga Basin and the Western Urals, which has significant implications for veterinary and public health surveillance.