IntroductionMalignant catarrhal fever (MCF) is a rare, under-explored lethal viral infection of cattle with gammaherpesvirus aetiological agents. Most often, the disease occurs on farms where cattle and sheep are kept together. However, other trigger mechanisms and environmental factors contribute. This study investigates the causation of MCF.Material and MethodsAn outbreak of MCF occurred in June - August 2017 in Kharchev village in Irkutsk Oblast, Russia. In this paper, we provide epidemiological (sanitary status of pastures, watering places, and premises) and weather data during the outbreak, and descriptions of the clinical signs and post-mortem changes in cattle. The virus was detected and isolated from pathological material samples and identified by molecular methods.ResultsExtreme weather conditions, mixed-herd cattle and sheep farming, and unsatisfactory feed quality contributed to the outbreak. A virus related to herpesvirus OvHV2 was isolated and typed (MCF/Irkutsk/2017). Phylogenetic analysis showed its close genetic relationship to isolates from cattle and sheep in Germany, USA, and the Netherlands.ConclusionSporadic outbreaks of MCF caused by biotic and abiotic factors together are typical for the Russian Federation, and the Irkutsk outbreak epitomised this. Temperature anomalies caused pasture depletion, resulting in feed and water deficiency for grazing animals and dehydration and acidosis. Heat stress in animals ultimately led to the occurrence of MCF in the herd.

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Rabies is endemic on the considerable part of the Russian Federation, and it is associated with current natural outbreaks of the infection. The highest animal morbidity rates are reported in the central and southern regions of the European part of Russia and in the southern part of Western Siberia. The Irkutsk Oblast is among the few regions of our country, which are rabies free for several decades. The research was aimed at the analysis of factors aiding to the maintenance of the rabies free status of the region. Retrospective study of archive and previously published reports on human and animal rabies cases in the Irkutsk Oblast starting from 1954 was performed. Epidemics of urban rabies ceased in the region in 1970s. Sporadic rabies cases in dogs, reported in 1976 and later, could be imported or could result from the infection from bats. Diagnostic errors were also possible. Rabies is reported in foxes in the Subjects bordering the Irkutsk Oblast: Krasnoyarsk Krai and Republic of Buryatia. It is supposed that in case of the infection introduction the forest-steppe agricultural areas near the Angara River are likely to be affected due to high population of foxes. Relative geographic isolation of the Irkutsk Oblast favors to the long animal rabies freedom of this territory. The vast area of mountain taiga with low fox population serves as an ecological barrier. In 2007–2009 and in 2019, barrier oral vaccination was carried out along the border with the Krasnoyarsk Krai and on the west coast of Baikal Lake. Measures for anti-rabies vaccination of dogs and cats were intensified. Active virological monitoring is performed on a regular basis. The paper demonstrates cartograms of fox and wolf population density along with designation of sites, where oral vaccination of wild carnivores was performed.

Equine piroplasmosis is a natural tick-borne infection caused by hemoprotozoan parasites of the order Piroplasmida, Babesia caballi and Theileria equi. Animals that recover from piroplasmosis remain persistently infected carriers and can transmit pathogens to vector ticks. Cases of equine piroplasmosis are periodically observed in Siberia, however, no agent of equine piroplasmosis has yet been genetically characterized in Russia. The aim of this work was studying the prevalence of the infectious agents of piroplasmosis in horses from Siberia and genotyping the detected agents. Blood samples from 155 horses were examined for the presence of Babesia and Theileria DNA by nested PCR with the subsequent sequencing of positive samples. DNA of T. equi was found in blood samples from 57.9 %, 38.5 % and 65.0 % of horses from Novosibirsk province, Irkutsk province, and the Republic of Altai, respectively. T. equi DNA was found in the samples from almost all sampling sites included in this study, indicating that most of the studied sites are endemic for equine theileriosis. Surprisingly, DNA of B. caballi was not found in any of the samples examined, even though this agent had previously been detected in many regions in Russia, including Altai. The analysis of the determined 18S rRNA gene sequences demonstrated that T. equi samples belonged to two genetic groups, which differed significantly by the sequences of the variable (V4) region of the gene. All T. equi sequences from group B were identical and corresponded to T. equi sequences found in the blood of horses from China and Korea, while T. equi sequences from group A differed by 1–5 nucleotide substitutions and were identical to the sequences from the blood of horses from India and Brazil or differed from them by single mismatches. Notably, in this study the presence of etiological agent of piroplasmosis in blood samples from horses in Russia was genetically confirmed for the first time.

The Baikal seal is the only endemic mammal of Lake Baikal. In late October 2017, 132 dead Baikal seals were found on the shore of the lake. To identify causes of death, postmortem necropsy, virological, chemical toxicological, microbiological, and parasitological studies were carried out. Several hypotheses for explaining the causes of the deaths were put forward. The most probable causes are heart failure and asphyxia due to echo sounders (sonar). The causes were confirmed by the results of histological examination of the hearts and lungs of a large number of dead seals found on the southern shore of Lake Baikal (a center for the fishing industry).