Outbreak of variant pseudorabies virus in Bartha-K61–vaccinated piglets in central Shandong Province, China

Abstract

An epidemic that mainly endangered 3–7-day-old piglets struck many farms in Shandong Province, China in 2013 and caused heavy losses. To identify the pathogenesis, the type of lesions, and the causative agent, systemic examinations were performed. Autopsy showed multiple lesions, including necrotic foci of the spleen and liver, punctate hemorrhage of the renal cortex, and interstitial pneumonia. Histological examinations showed typical nonsuppurative encephalitis, necrotic lymphocytes, and reticuloendothelial cells in lymphatic tissues, as well as eosinophilic inclusion bodies in the nuclei of reticuloendothelial cells, necrotic foci in liver cells, and hemorrhagic glomeruli. The average seroprevalence rate of field pseudorabies virus (PRV; Suid herpesvirus 1) of a representative farm tested by enzyme-linked immunosorbent assay was 46%, indicating that the PRV infectious pressure was quite severe especially among gilts, young multiparous sows, boars, and growing–finishing pigs. The glycoprotein E (gE) gene of PRV was detected in 8 of 10 clinical samples, and the virus in the positive samples induced obvious cytopathic effects. An immunoperoxidase monolayer assay showed that PRV antigens were distributed both in the nucleoli and cytoplasm of infected cells. Sequencing and phylogenetic analysis of the gE gene showed that the strain isolated herein, TaiAn SD 2013, was highly similar to previously isolated strains, especially those isolated in northern China in 2013, and was closely related to other isolates from Asia. Evidence confirmed that the variant PRV was the etiologic agent of this epidemic, suggesting that the Bartha-K61 vaccine does not provide complete protection against PRV infection. Further challenge tests are ongoing to investigate the virulence of variant PRV.

Genetic Diversity and Positive Selection Analysis of Classical Swine Fever Virus Envelope Protein Gene E2 in East China under C-Strain Vaccination

“…Viral DNA and RNA of the harvested cultures were extracted using the EasyPure viral DNA/RNA kit (TransGen, Beijing, China) according to the manufacturer’s instructions for the detection of suspected viruses. Four major pathogens, including CSFV, PRRSV, PRV, and PCV2 were detected by PCR or reverse transcription (RT)-PCR ( Hu et al, 2015 ).…”

Seroprevalence and associated risk factors of pseudorabies in Shandong province of China

“…In China, an outbreak of PRV was first reported in the 1950s, and the Bartha-K61 vaccine was imported from Hungary to China in the 1970s. From the 1990s until late 2011, > 80% of pigs in China were vaccinated with the Bartha-K61 vaccine, and PR was well controlled [ 1 9 ]. However, since late 2011, a severe PR epidemic characterized by abortions and stillbirths of sows, as well as neurological signs and high-mortality among newborn piglets, has occurred in many pig herds immunized with live PRV vaccines in many regions of China [ 1 14 29 30 ].…”

Pseudorabies virus (PRV) strain with defects in gE, gC, and TK genes protects piglets against an emerging PRV variant

“…Thus, Chinese farms urgently require the development of a novel vaccine to control the emerging PRV variant. At present, various vaccines have been reported, such as inactivated PRV (Fujian strain) and HB (Hubei strain) vaccines, as well as live attenuated vaccines of the HB-98 strain with a TK/gC double gene deletion, apart from SA215 strain (PRV) with a gE/gI/TK gene deletion, and HB2000 strain with a TK/gG/gE 3 gene deletion [2,6,12,28]. However, these vaccines have been shown to be poorly effective at protecting pigs, according to recent clinical data, which revealed an average positive PRV rate of 8.27% between 2012 and 2017, indicating that PRV-vaccines currently used in China still show a high risk of PR prevalence [8,10].…”