Atypical porcine pestivirus (Pestivirus K) - a new challenge for pig farming (review)

Pestiviruses are highly variable RNA viruses of the genus Pestivirus , family Flaviviridae . The genus Pestivirus includes 11 species, from Pestivirus A to Pestivirus K (B.G. Orlyankin et al., 2020; D.B. Smith et al., 2017; A.M.Q. King et al., 2018). In the infectious pathologies of pigs, pestiviruses are highly important due to significant economic losses. Over the past two decades, many previously undescribed pestiviruses have been found in domestic pigs and wild boars. Due to the tendency to rapid spread, they can cause a serious threat to pig production. In 2015, in the framework of the Porcine Reproductive and Respiratory Syndrome Virus genetic diversity project in the US, an atypical porcine pestivirus ( Pestivirus K ) was first identified in blood serum by metagenomic sequencing. Initially, it was assumed that pigs infected with atypical pestivirus did not show clinical signs of the disease. However, the experiments on the study of atypical pestivirus infectious properties showed that the pestivirus causes congenital tremor (CT) type A-II in piglets (B.L. Arruda et al., 2016; A. de Groof et al., 2016; A. Postel et al., 2017). Adult domestic pigs and wild boars are also susceptible to the virus. Atypical porcine pestivirus is transmitted vertically and horizontally and is widespread in many countries of Europe, America and Asia. In Russia, atypical porcine pestivirus has not been diagnosed in pigs. The phylogenetic analysis of the genome of all known isolates revealed 3 genetic groups (1st-3d) and seven subgenotypes within the 1st genetic group (1.1-1.7) of the virus (F. Yuan et al., 2021). The first genetic group includes all isolates identified in the USA, Europe and several isolates from China. The second and third genetic groups are isolates from China only. The circulation of atypical porcine pestivirus in herds can complicate the differential diagnosis of classical swine fever, due to some similarity of symptoms, the congenital tremor particularly. Consequently, the knowledge of the epidemiology of the atypical porcine pestivirus in different geographic regions will help optimization of its control and prevention of spreading. The review covers current data of the etiology, distribution, clinical manifestations, diagnosis and prevention of the atypical porcine pestivirus infection.