Phylogenetic characteristics of the porcine reproductive and respiratory syndrome virus isolated from pigs in four regions of Kazakhstan

Porcine reproductive and respiratory syndrome (PRRS) causes serious reproductive and respiratory effects in pig populations worldwide. The aim of this study was to determine the seroprevalence and phylogenetic relationships of field isolates of the PRRS virus (PRRSV) in pig populations in four regions of Kazakhstan. A representative sample of 323 pigs was selected to establish the seroprevalence of PRRSV in the study area. A serological test for detecting antibodies (ELISA) was performed, and the genetic characteristics of the virus were examined using the PCR method. Virus isolation from the blood sample, MARC-145, cell cultures were used. In total, 13.93% of the tested serum samples (n=45) revealed seropositivity against PRRSV antibodies. The genetic sequencing of the isolated strains indicated the widespread circulation of the North American genotype in the Almaty region. These results were confirmed by the cytopathic effects observed in cell cultures. Molecular analysis showed that the local strains have undergone significant genetic drift from the sequenced European strains and are phylogenetically more closely related to strains originating from North American. The results of genetic analyses indicate that the North American genotype has become established in Kazakhstan. This situation requires increased use of biosecurity systems and vaccines specific for this genotype. Our results highlight the importance of continuous monitoring and an active adaptive management system in controlling the spread of PRRS in regional pig populations.