Comprehensive Diagnosis of Pseudorabies in Pigs and Analysis of Genetic Variation of gE and TK Genes in Isolated Strains

Since 2012, many pig farms immunized with gE gene deleted live vaccines have been extensively infected with PRV (pseudorabies virus), and the positive rate of gE antibody has been increasing, and the typical cases of pseudorabies have been increasing. In March 2018, suspected pseudorabies occurred in several breeding pig farms in Lunan region of Shandong province. Pregnant sows miscarried, stillborn and mummified fetuses, and piglets showed neurological symptoms and high mortality rate. A preliminary diagnosis was carried out on the dead pigs and dead embryos, and the histopathological diagnosis,virus isolation and identification were further carried out. The results showed that pathological changes such as viral encephalitis, degeneration and necrosis of hepatocytes and lymphoid tissue necrosis were all observed in the dead pigs. Red stained inclusion bodies were found in the nucleus of the neurons, hepatocytes and tonsil crypt epithelial cells. The sequence analysis and genetic variation analysis of the gE and TK genes of the four strains of PRV isolated showed that the homology of the gE and TK nucleotide sequences of the four strains of PRV were 98.8%-99.3% and 98.9%-99.6%, respectively. The identity with the nucleotide sequences of the domestic strains were 99.1%-99.7% and 98.6%-99.8%, and the similarity with the nucleotide sequence of Hungarian and American strains were 97.3%-97.8% and 98.8%-99.5% respectively, which indicated that the four isolated strains are highly homologous, and they are in the same branch with the domestic PRV mutants, while they are far away from the Hungarian and American strains in the distance of inheritance. The traditional vaccine cannot provide effective protection for the mutant strains of PRV, which brings new challenges to the prevention and purification of eradication in pig farms.

CSTR: 32200.14.cjcb.2020.01.0005