Blood parasites and bacteria of Muroidea rodents of the Chornobyl Exclusion Zone.

The Chornobyl Exclusion Zone (ChEZ) is a unique area in the world. It combines two things: the largest man-made disaster site in the world and a radioecological observatory. The observatory has been studying the long-term impact of radioactive contamination on the environment, flora and fauna since 1986. Muridae and Cricetidae rodents being extremely widespread representatives of ChEZ fauna, serve as bioindicators for radioecological research. During 2019-2020, in addition to studying rodents as markers of radioactive contamination, 116 muroids were examined for the presence of parasites and bacteria. Among the rodents studied were bank voles Myodes glareolus from the Cricetidae family, as well as yellow-necked mice Apodemus (Sylvaemus) flavicollis and striped field mice Apodemus agrarius of the Muridae family. Microscopy of muroid rodent blood films revealed the presence of Trypanosoma spp., Hepatozoon spp. and bacterial agents. Molecular analyses led to the first identification of Trypanosoma grosi in A. agrarius in Ukraine. A Hepatozoon spp. SK3-type was found for the first time in A. flavicollis. Three different genotypes of Mollicutes were detected in A. agrarius and A. flavicollis. Bartonella spp. were present in most of the rodents tested. Zoonotic Bartonella grahamii was identified among six isolated genotypes of Bartonella. Co-infections with parasites and bacteria were found in some animals. According to microscopic studies, A. agrarius had the highest prevalence of Trypanosoma spp., whereas Hepatozoon spp. was highest in M. glareolus. Meanwhile, A. flavicollis harboured the greatest diversity of genotypes according to the sequencing results. Interestingly, a 41.7% prevalence of T. grosi and 33.3% of Mycoplasma-like bacteria was detected by PCR among animals from landfill II of the ChEZ, which was the least contaminated of the four experimental sites in the Exclusion Zone. Further research should be conducted to identify pathogens of viral origin and to study more genome loci of parasites in order to determine the impact of radioactive contamination that microorganisms may be exposed to.