Atypical porcine pestivirus-A widespread virus in the Swedish wild boar population

Isolation and Phylogenetic Analysis of Atypical Porcine Pestivirus Isolates Identified in Russian Swine Herds

Atypical porcine pestivirus (APPV) was first identified in 2015 in North America by high-throughput sequencing. APPV is associated with congenital tremor A-II and is widely distributed worldwide. In this study, a total of 2630 samples of domestic pigs obtained from 14 regions of Russia from 2020 to 2024 were screened for APPV presence by qRT-PCR. APPV was detected in 12 farms located in eight regions. The overall positive rate was 8.8%. It has been established that APPV has been circulating in Russian swine herds since at least 2020. The phylogenetic analysis demonstrated that the Russian isolates are variable and assigned into three clusters. The isolates from the Krasnoyarsk Krai, Belgorod, Tomsk, and Kursk regions and the Republic of Buryatia share a high nucleotide identity (94.3-98.8%) with the Hungarian strains, while the isolates from the Moscow and Pskov regions share a nucleotide identity (89.2-94.3%) with strains from the USA. The isolate from the Republic of Mordovia has a high nucleotide identity (97.1%) with the South Korean strain. In vitro studies of the Russian isolates revealed the replication of the Belgorod 151 strain in SPEV cells. Thus, this is the first large-scale study that confirms the circulation of APPV in swine herds in Russia and describes its isolation in cell culture.

No evidence of spread of Linda pestivirus in the wild boar population in Southern Germany

Lateral-shaking inducing neuro-degenerative agent virus (LindaV) is a novel member of the highly diverse genus Pestivirus within the family Flaviviridae. LindaV was first detected in Austria in 2015 and was associated with congenital tremor in piglets. Since then, the virus or specific antibodies have been found in a few further pig farms in Austria. However, the actual spatial distribution and the existence of reservoir hosts is largely unknown. Since other pestiviruses of pigs such as classical swine fever virus or atypical porcine pestivirus can also infect wild boar, the question arises whether LindaV is likewise present in the wild boar population. Therefore, we investigated the presence of neutralizing antibodies against LindaV in 200 wild boar samples collected in Southern Germany, which borders Austria. To establish a serological test system, we made use of the interchangeability of the surface glycoproteins and created a chimeric pestivirus using Bungowannah virus (species Pestivirus australiaense) as synthetic backbone. The E1 and E2 glycoproteins were replaced by the heterologous E1 and E2 of LindaV resulting in the chimera BV_E1E2_LV. Viable virus could be rescued and was subsequently applied in a neutralization test. A specific positive control serum generated against the E2 protein of LindaV gave a strong positive result, thereby confirming the functionality of the test system. All wild boar samples, however, tested negative. Hence, there is no evidence that LindaV has become highly prevalent in the wild boar population in Southern Germany.

Network of Interactions between the Mut Domains of the E2 Protein of Atypical Porcine Pestivirus and Host Proteins

Atypical porcine pestivirus (APPV) can cause congenital tremor type A-II in neonatal piglets, posing a significant threat to swine herd health globally. Our previous study demonstrated that the Mut domains, comprising 112 amino acids at the N-terminus, are the primary functional regions of the E2 protein of APPV. This study identified 14 host cellular proteins that exhibit potential interactions with the Mut domains of the E2 protein using yeast two-hybrid screening. Using bioinformatics analysis, we discovered that the Mut domains of the E2 protein might exert regulatory effects on apoptosis by modulating energy metabolism within the mitochondria. We also conducted co-immunoprecipitation, glutathione S-transferase pull-down, and immunofluorescence assays to confirm the interaction between the Mut domains of the E2 protein and cathepsin H and signal sequence receptor subunit 4 (SSR4). Ultimately, SSR4 enhanced APPV replication in vitro. In summary, our study successfully elucidated the interactions between the Mut domains of the E2 protein and host cell protein, predicted the potential pathways implicated in these interactions, and demonstrated SSR4 involvement in APPV infection. These significant findings contribute valuable knowledge toward a deeper understanding of APPV pathogenesis and the role of the Mut domains of the E2 protein in this intricate process.

Development and application of an indirect ELISA for detection of antibodies against emerging atypical porcine pestivirus

BACKGROUND

Atypical porcine pestivirus (APPV) is a newly discovered swine pestivirus, which can cause congenital tremor and high mortality in newborn piglets and subclinical infection in adult pigs, leading to significant impacts on the pig industry. Currently, there is no approved serological method to assess APPV infection status in pig farms.

METHODS

In this study, the envelope glycoprotein E2 of APPV was highly expressed in suspension HEK293 cells, and further an indirect enzyme-linked immunosorbent assay based on the recombinant E2 protein (E2-iELISA) was developed and evaluated.

RESULTS

The reaction parameters of the E2-iELISA were optimized, and the cutoff value was determined to be 0.2 by analyzing S/P values of 165 negative sera against APPV that were confirmed by virus neutralization test (VNT). Specificity test showed that the method had no cross-reaction with other common swine viruses. The E2-iELISA was evaluated using a panel of swine sera, and showed high sensitivity (113/120, 94.2%) and specificity (65/70, 92.9%), and the agreement rate with VNT was 93.7% (178/190). Subsequently, the E2-iELISA was utilized to investigate the seroprevalence of APPV in pig herds of China. When detecting 1368 pig serum samples collected from nine provinces in China, the overall seroprevalence of APPV was 73.9% (1011/1368).

CONCLUSION

Our findings suggest that the E2-iELISA is specific and sensitive, and could be a valuable tool for serological surveillance of APPV infection in pigs.

Isolation and artificial production of atypical porcine pestivirus, using the swine-kidney-derived cell line SK-L

Congenital tremor (CT) in piglets was first reported in 1922, and although the causative pathogen was unknown for many years, atypical porcine pestivirus (APPV) was recently shown to be the cause. APPV is difficult to isolate, and there have been few reports of APPV isolated from field materials. Here, we successfully isolated infectious particles from a tonsillar emulsion from a CT-affected piglet using the established swine-kidney-derived cell line SK-L. In addition, we produced APPV artificially using these cells. Thus, SK-L cells are useful for both isolation and artificial production of APPV.

Screening for atypical porcine pestivirus in Swedish boar semen used for artificial insemination and a characterisation of the seminal RNA microbiome including the virome

BACKGROUND

This study aimed to characterise the RNA microbiome, including the virome of extended semen from Swedish breeding boars, with particular focus on Atypical porcine pestivirus (APPV). This neurotropic virus, associated with congenital tremor type A-II in piglets, was recently demonstrated to induce the disease through insemination with semen from infected boars.

RESULTS

From 124 Artificial Insemination (AI) doses from Swedish breeding boars, APPV was detected in one dose in addition to a sparse seminal RNA virome, characterised by retroviruses, phages, and some fecal-associated contaminants. The detected seminal microbiome was large and characterized by Gram-negative bacteria from the phylum Proteobacteria, mainly consisting of apathogenic or opportunistic bacteria. The proportion of bacteria with a pathogenic potential was low, and no antimicrobial resistance genes (ARGs) were detected in the datasets.

CONCLUSION

Overall, the results indicate a good health status among Swedish breeding boars. The detection of APPV in semen raises the question of whether routine screening for APPV in breeding boars should be instigated.

First Detection of Salmonella enterica Serovar Choleraesuis in Free Ranging European Wild Boar in Sweden

Following the first detection of Salmonella enterica subsp. enterica, serovar Choleraesuis (S. Choleraesuis) in a Swedish pig herd for more than 40 years and subsequent detection of the same serotype in an enclosure with kept wild boar, a national surveillance for S. Choleraesuis in free living wild boar was launched. A total of 633 wild boar sampled within the active and the enhanced passive surveillance were examined for Salmonella enterica serovars by culture. Of these, 80 animals were culture positive for S. Choleraesuis var. Kunzendorf. All positive animals, including those in the original outbreaks, originated from counties located in the southern and eastern parts of Sweden. Fifty-eight isolates were selected for sequence typing, revealing a relatively homogenous population of S. Choleraesuis with two distinct genetic clusters containing isolates from the southern counties in one and the counties further northeast in the other. Sequenced isolates from domestic pig farms all clustered with wild boar in the same region. S. Choleraesuis appears highly contagious in dense wild boar populations, making it a relevant model for other infectious diseases that may be transmitted to pigs. The many potential routes of introduction and spread of S. Choleraesuis warrant further investigations in order to prepare for other disease threats.