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Botvinkin et al. One Health Implement Res 2023;3:125-34 https://dx.doi.org/10.20517/ohir.2023.19 Page 129

Table 2. Laboratory-confirmed rabies cases in the ARR during 2018-2022
Case number by years
Species Proportion, % (95%CI)
2018 2019 2020 2021 2022 total
Red fox 10 5 2 2 0 19 38.8 (25.2-52.4)
Wolf 0 3 2 2 0 7 14.3 (4.5-24.1)
Raccoon dog 3 1 0 1 0 5 10.2 (1.7-18.7)
Dog 0 1 1 6 1 9 18.4 (7.6-29.2)
Cattle 2 1 0 4 1 8 16.3 (6.0-26.6)
Horse 1 0 0 0 0 1 2.0 (0.0-6.0)
Total 16 11 5 15 2 49 100
ARR: Amur Region of Russia.

The main reservoir of the RABV during this recent outbreak was represented by wild carnivores, which
accounted for 53.3% of all reported cases. Most often, especially at the beginning of the outbreak, the
infection was detected in foxes [Table 2]. Dog rabies was reported mainly at the end of the analyzed period
and mostly among stray dogs.

During 2018-2022, rabies spread within the forest-steppe and agricultural landscapes of the Zeya-Bureya
Plain. The successive spread of rabies, mainly in the north and northwest direction from the place of first
detection, can be traced on the map [Figure 1]. During the first epizootic cycle (2018-2019), the median of
the distance from the primary case to other cases was 23.8 (7-107.2) km; in 2019-2020, it was 112.4 (77.6-
128.9) km; in 2020-2021, it was 150.1 (57.1-192.4) km; in 2021-2022, it was130.7 (57.1-121.4) km. The
maximum distance from the first recorded event was 192.4 km for the observation period (Me = 77.6). As
the epizootic wave progressed, cases in the initially affected areas decreased.

A full-size N gene nucleotide sequence (1,353 nt) of the RABV isolate from the first case in cows was
determined, as well as 1,110 nt N gene fragments of six isolates from red foxes, raccoon dogs, and a horse
and 556 nt N gene fragment of the two wolf isolates. The results of the phylogenetic analysis are shown in
Figure 2 and Supplementary Table 2. The isolates from wolves (Amur8944w and Amur8946w) were not
included in the tree because of the short lengths of their sequenced N gene fragment to prevent a decrease
in tree resolution. The compared genome regions of the isolates collected during the first two months after
outbreak detection were identical or differed by no more than one nucleotide. Thus, at the beginning of the
outbreak, the ARR sequences shared 99.9%-100% identity. The genetic homogeneity of the isolates suggests
a single initial source of the infection. It has been determined that isolates from the ARR belonged to the
Arctic-like-2 genetic group of RABV and had a high degree of similarity (95.0%-99.4%) with isolates from
neighboring regions of Russia and Northern China. They showed the maximum similarity to the TJ11-RD
isolate from a goat (Tongjiang city, Heilongjiang province, China, 2011) - 99.4%, the HLJ01 isolate from a
raccoon dog from the same province (the exact location is not known, 2018) - 98.6 %, as well as to isolate
857r from a raccoon dog (Leninskoe settlement, JAR, Russia, 1980) - 98.9%. It should be emphasized that
the Leninskoye settlement in Russia and the Tongjiang city in China are located approximately 30 km from
each other on opposite banks of the Amur River. Thus, this lineage of the RABV circulated in the Middle
Amur Plain on both banks of the Amur River since 1980. The isolates also demonstrated 97.6%-98.3%
nucleotide identity to Arctic-like-2 RABV sequences recovered in other regions of Russia, Northern China
(Hebei, Jilin, Liaoning, and Inner Mongolia), and South Korea from 1977 to 2020. Even the identity of
Japanese isolate Komatsugava recovered during the 1940s was as much as 97.2%. The genetic similarity of
isolates from the ARR with RABV of the Arctic-like-1, Arctic, Steppe, and South-East Asia 1 (China-1)
lineages does not exceed 92%.