Determination of the rabies virus variants circulating in Poland in 2021-2023 and their phylogeny with analysis of the strains in the Mazowieckie and Podkarpackie voivodeships.

Introduction: Rabies is endemic in Europe and red foxes are the vector and reservoir of the rabies virus (RABV). Based on classification established in the early 1990s, four variants of the rabies virus have been distinguished in Europe. Rabies broke out in January 2021 in the Mazowieckie voivodeship in central north-eastern Poland. The virus spread rapidly, reaching the Świętokrzyskie voivodeship in the central southern part and the Lubelskie voivodeship in the eastern part in the next months. Nine rabies cases were reported in the Podkarpackie voivodeship in south-eastern Poland between 2021 and 2023, mainly in red foxes but also in dogs and wildcat. The aim of the study was the identification of RABV variants in wildlife and domestic animals in Poland between 2021 and 2023.

Material and methods: The study involved 157 animal brains tested positive for rabies using a fluorescent antibody test. From 10% w/v brain homogenates, RNA was isolated and full-length RABV genomes were high-throughput sequenced with an RABV-enriched approach. Complete genomes of RABV isolates were phylogenetically analysed and the variants were estimated.

Results: Molecular and phylogenetic studies revealed 147 (93.6%) of the RABV strains out of 157 which had rapidly spread in the wildlife of the Mazowieckie, Świętokrzyskie and Lubelskie voivodeships to be Central European strains. Nine RABVs (5.7%) detected in foxes, a wildcat and a dog in the Podkarpackie voivodeship were identified as North-Eastern European. A vaccine-induced rabies case was detected in a red fox in the Lubelskie voivodeship in May 2023.

Conclusion: Central European and North-Eastern European RABVs were circulating in Poland between 2021 and 2023.