Reconstruction of epizootic outbreak provoked the largescale death of Rhinoceros auklet on the coast of the Japan Sea in the Southern part of Primorsky Krai (July, 2021)

Introduction. In July 2021, a mass mortality of seabirds of unclear etiology occurred on the coast of the Sea of Japan in the Khasansky district of Primorsky Krai. According to the Department for Protection of Wildlife and Specially Protected Natural Territories of Primorsky Krai, over a thousand dead birds were found on the coast. The main case occurred in the population of birds Rhinoceros auklets (Cerorhinca monocerata, Alcidae), also among the dead birds were found several dozens of gulls (Larus spp.) and terns (Sterna spp.), single individuals of other species. The peak of mortality in bird populations occurred on July 13–17, 2021. This territory is a recreational area, in the summer months a large number of people rest there. The current situation has caused increased attention of the entire scientific community, as well as organizations that protect the citizens health and the environment. The aim. To establish possible etiology of the epizootic outbreak and describe the cause of birds’ death.Materials and methods. Comprehensive examination using classical methods of virology, microbiology and toxicology, as well as the most modern research methods such as MALDI TOF-mass spectrometry and NGS.Conclusion. As a result of the studies, it was determined that the cause of birds’ death was infectious peritonitis with endogenous intoxication syndrome induced by a complex of pathogenic microorganisms, such as enteropathogenic Escherichia coli, Proteus vulgaris, Proteus mirabilis, Proteus pennery, Enterococcus faecalis and Wickerhamomyces anomalus, related to Candida pelliculosa