Dynamics of Infection of Atypical Porcine Pestivirus in Commercial Pigs from Birth to Market: A Longitudinal Study.

Atypical porcine pestivirus (APPV) was found to be associated with pigs demonstrating congenital tremors (CT), and clinical signs in pigs have been reproduced after experimental challenge. Subsequently, APPV has been identified in both symptomatic and asymptomatic swine of all ages globally. The objective of this research was to perform a longitudinal study following two cohorts of pigs, those born in litters with pigs exhibiting CT and those born in litters without CT, to analyze the virus and antibody dynamics of APPV infection in serum from birth to market. There was a wide range in the percentage of affected pigs (8-75%) within CT-positive litters. After co-mingling with CT-positive litters at weaning, pigs from CT-negative litters developed viremia that was cleared after approximately 2 months, with the majority seroconverting by the end of the study. In contrast, a greater percentage of pigs exhibiting CT remained PCR positive throughout the growing phase, with less than one-third of these animals seroconverting. APPV RNA was present in multiple tissues from pigs in both groups at the time of marketing. This study improved our understanding of the infection dynamics of APPV in swine and the impact that the immune status and timing of infection have on the persistence of APPV in serum and tissues.

Distribution and persistence of atypical porcine pestivirus in experimentally inoculated pigs.

Atypical porcine pestivirus (APPV) is a cause of congenital tremors (CTs) in piglets and has been found in swine populations around the globe. Although systemic distribution of the virus has been reported, there is limited information regarding viral localization at the cellular level and distribution at the tissue level. We collected multiple tissues from 2-d-old piglets (n = 36) born to sows inoculated at 45 or 62 d of gestation with APPV via 3 simultaneous routes: intravenous, intranasal, and directly in amniotic vesicles. In addition, 2 boars from APPV-inoculated sows with CT were raised and euthanized when 11 mo old. In situ hybridization performed on tissue samples from piglets demonstrated a broad and systemic distribution of viral RNA including endothelial cells, fibroblasts, and smooth muscle. Labeling in tissues was more pronounced in piglet tissues compared to boars, with the notable exception of diffuse labeling of the cerebellum in boars. Presence of APPV in boar tissues well after resolution of clinical signs suggests persistence of APPV similar to other pestiviruses.

12 novel atypical porcine pestivirus genomes from neonatal piglets with congenital tremors: A newly emerging branch and high prevalence in China.

Atypical porcine pestivirus (APPV), a newly discovered member of the genus Pestivirus, is considered to be associated with congenital tremors (CT) in piglets. From June 2016 to January 2018, 440 serum and tissue samples from CT-affected piglets in Anhui, Guangdong and Guangxi provinces were collected to detect APPV. The results showed a high level of 63.4% preference for APPV in 27 swine farms and complicated co-infection cases between APPV and other 12 swine viruses. Meanwhile, 12 novel APPV genomes were screened and identified. Results showed that complete genomes, Npro and NS5A genes of these novel 12 APPV sequences revealed 80.5%-99.8%, 78%-100% and 76.9%-99.8% nucleotide identities, respectively. Phylogenetic analyses based on sequences of full-length genomes, Npro and NS5A genes of APPV indicated three well-defined clades including a newly emerging branch in China. This study provides novel epidemiological information of APPV in China.

Phylogenetic and genomic characterization of a novel atypical porcine pestivirus in China.

Atypical porcine pestivirus (APPV) has been considered a novel pestivirus and causative agent of congenital tremor type A-II. An APPV CH-GX2016 strain was characterized from newly born piglets with clinical symptoms of congenital tremor in Guangxi, China. The genome of APPV CH-GX 2016 strain was 11,475 bp in length and encoded a polyprotein composed of the 3,635 amino acids. This genome sequence exhibited 88.0% to 90.8% nucleotide sequence homology with other APPV reference sequences in GenBank. Phylogenetic analysis further showed that APPV CH-GX is a novel pestivirus compared with previously described classical pestivirus strains. Therefore, APPV is present in pigs in China.

Detection and genome sequencing of porcine circovirus 3 in neonatal pigs with congenital tremors in South China.

Porcine circovirus 3 (PCV3) is a novel circovirus first discovered in the United States in piglets and sows with porcine dermatitis and nephropathy syndrome, reproductive failure, cardiac and multisystemic inflammation. Here, seven PCV3 strains were identified for the first time from neonatal pigs with clinical signs of congenital tremors (CT) in South China. The tissue tropism of PCV3 in CT-affected piglets was analysed by the real-time quantitative PCR, and the result showed that high loads of viral genomes were detected in the brains and hearts. The complete genomes of seven new PCV3 revealed 96.8%-99.6% nucleotide identities with eleven other PCV3 strains previously reported from the United States and China. Phylogenetic analysis based on the complete genome sequences showed that all PCV3 strains clustered together and were clearly separated from other circovirus species. This study reports on the first identification of PCV3 in CT-affected newborn piglets and provides the epidemiological information of neonatal piglets with CT in Guangdong and Guangxi Provinces of China.