This paper describes the detection of Piroplasmida DNA in the blood of horses. 166 blood samples of horses from five districts of the Irkutsk region were studied. The high piroplasms infection rate in horses (69 %) was found. For six positive samples nucleotide sequences were determined. The comparison of determined 18S rRNA gene sequences with previously published sequences showed that all revealed piroplasms DNA samples are Theileria equi. The data are presented on the lethal cases of equine piroplasmosis in the Irkutsk region in 2008.

New data was obtained about the original version of tickborne encephalitis virus (TBE), circulating in the territory of Eastern Siberia. With the help of molecular hybridization of nucleic acids (MGNA) and genome sequencing we revealed a group of 13 strains having a genetic structure analogous to strain 886-84, which was described earlier as the sole representative of the probable genotype 5. The formation of a separate cluster on the phylogenetic tree, differentiation level of genetic differences from other genotypes more than 12 %, own habitat, ecological relationship with all the links of a vector-borne chain, participation in human pathology, the stability and duration of circulation in nature confirms the validity of certification of «group 886» as a separate TBEV genotype 5.