Assessing the risk of recurrence of porcine epidemic diarrhea virus in affected farms on Jeju Island, South Korea

Antiviral activity of chrysin and naringenin against porcine epidemic diarrhea virus infection

Porcine epidemic diarrhea virus (PEDV) is one of the critical pathogens causing diarrhea in piglets and has caused huge economic losses to the swine industry in worldwide. However, there is currently no effective therapeutic medication available for the treatment of PEDV. Natural compounds are a hot topic for researching and screening antiviral lead compounds due to their abundant sources, varied activities, and low toxicity. In this study, a total of 6 compounds from different plant sources were selected for in vitro anti-PEDV screening, including chrysin, naringenin, soy isoflavone, glycyrrhetinic acid, oleanolic acid, and geniposide. Then two active compounds, chrysin and naringenin, were further evaluated on PEDV infected cells at different stage. And the anti-PEDV mechanism was analyzed by molecule docking and molecular dynamics. The results showed that both chrysin and naringenin showed the most significant anti-PEDV activity by increasing the cell viability and decreasing the virus copy number. Both natural compounds could inhibit viral titer, mRNA and protein levels in the prophylactic and post-viral entry stages of PEDV infection. Furthermore, chrysin and naringenin mainly interacted with viral replicase proteins such as 3CLpro and PLP-2 through hydrogen bonds and hydrophobic forces. The complexes formed by chrysin and naringenin with the two PEDV replication proteases had high stability. These results suggested that chrysin and naringenin may exert antiviral effects by interacting with the virus 3CLpro protein or PLP2 protein, thereby affecting their role in the formation of PEDV non-structural proteins or interfering with virus replication. This study lays the foundation for developing chrysin and naringenin as novel anti-PEDV therapeutic drugs.

Porcine epidemic diarrhea virus: an update overview of virus epidemiology, vaccines, and control strategies in South Korea

Porcine epidemic diarrhea virus (PEDV) has posed significant financial threats to the domestic pig industry over the last three decades in South Korea. PEDV infection will mostly result in endemic persistence in the affected farrow-to-finish (FTF) herds, leading to endemic porcine epidemic diarrhea (PED) followed by year-round recurrent outbreaks. This review aims to encourage collaboration among swine producers, veterinarians, and researchers to offer answers that strengthen our understanding of PEDV in efforts to prevent and control endemic PED and to prepare for the next epidemics or pandemics. We found that collaboratively implementing a PED risk assessment and customized four-pillar-based control measures is vital to interrupt the chain of endemic PED in affected herds: the former can identify on-farm risk factors while the latter aims to compensate for or improve weaknesses via herd immunity stabilization and virus elimination. Under endemic PED, long-term virus survival in slurry and asymptomatically infected gilts ("Trojan Pigs") that can transmit the virus to farrowing houses are key challenges for PEDV eradication in FTF farms and highlight the necessity for active monitoring and surveillance of the virus in herds and their environments. This paper underlines the current knowledge of molecular epidemiology and commercially available vaccines, as well as the risk assessment and customized strategies to control PEDV. The intervention measures for stabilizing herd immunity and eliminating virus circulation may be the cornerstone of establishing regional or national PED eradication programs.

Natural Evolution of Porcine Epidemic Diarrhea Viruses Isolated from Maternally Immunized Piglets

The porcine epidemic diarrhea virus (PEDV) can cause severe piglet diarrhea or death in some herds. Genetic recombination and mutation facilitate the continuous evolution of the virus (PEDV), posing a great challenge for the prevention and control of porcine epidemic diarrhea (PED). Disease materials of piglets with PEDV vaccination failure in some areas of Shanxi, Henan and Hebei provinces of China were collected and examined to understand the prevalence and evolutionary characteristics of PEDV in these areas. Forty-seven suspicious disease materials from different litters on different farms were tested by multiplex PCR and screened by hematoxylin-eosin staining and immunohistochemistry. PEDV showed a positivity rate of 42.6%, infecting the small and large intestine and mesenteric lymph node tissues. The isolated strains infected Vero, PK-15 and Marc-145 multihost cells and exhibited low viral titers in all three cell types, as indicated by their growth kinetic curves. Possible putative recombination events in the isolates were identified by RDP4.0 software. Sequencing and phylogenetic analysis showed that compared with the classical vaccine strain, PEDV SX6 contains new insertion and mutations in the S region and belongs to genotype GIIa. Meanwhile, ORF3 has the complete amino acid sequence with aa80 mutated wild strains, compared to vaccine strains CV777, AJ1102, AJ1102-R and LW/L. These results will contribute to the development of new PEDV vaccines based on prevalent wild strains for the prevention and control of PED in China.

Phylogenetic and Spatiotemporal Analyses of Porcine Epidemic Diarrhea Virus in Guangxi, China during 2017–2022

Since 2010, porcine epidemic diarrhea virus (PEDV) has swept across China and spread throughout the country, causing huge economic losses. In this study, 673 diarrhea samples from 143 pig farms in Guangxi during 2017–2022 were collected and detected for PEDV. Ninety-eight strains were selected for S1 gene analyses and these strains were classified into four subgroups (G1b, G2a, G2b and G2c), accounting for 1.02 (1/98), 75.51 (74/98), 16.33 (16/98) and 7.14% (7/98) of the total, respectively. Importantly, an increased number of strains in the G2c subgroup was found from 2019 onwards. Bayesian analysis revealed that Guigang may have been the epicenter of PEDVs in Guangxi. In addition, Guigang was identified as the primary hub from which PEDVs spread via two routes, namely Guigang–Wuzhou and Guigang–Laibin. Moreover, several coinfections of novel PEDV variants bearing large deletions in the partial S1 protein and PEDVs possessing an intact partial S1 protein were found in pigs. Further recombination analyses indicated that two of the strains, 18-GXNN-6 and 19-GXBH-2, originated from intra-genogroup recombination. Together, our data revealed a new profile of PEDV in Guangxi, China, which enhances our understanding of the distribution, genetic characteristics and evolutionary profile of the circulating PEDV strains in China.

Triacetyl Resveratrol Inhibits PEDV by Inducing the Early Apoptosis In Vitro

PEDV represents an ancient Coronavirus still causing huge economic losses to the porcine breeding industry. Resveratrol has excellent antiviral effects. Triacetyl resveratrol (TCRV), a novel natural derivative of resveratrol, has been recently discovered, and its pharmacological effects need to be explored further. This paper aims to explore the relationship between PEDV and TCRV, which offers a novel strategy in the research of antivirals. In our study, Vero cells and IPEC-J2 cells were used as an in vitro model. First, we proved that TCRV had an obvious anti-PEDV effect and a strong inhibitory effect at different time points. Then, we explored the mechanism of inhibition of PEDV infection by TCRV. Our results showed that TCRV could induce the early apoptosis of PEDV-infected cells, in contrast to PEDV-induced apoptosis. Moreover, we observed that TCRV could promote the expression and activation of apoptosis-related proteins and release mitochondrial cytochrome C into cytoplasm. Based on these results, we hypothesized that TCRV induced the early apoptosis of PEDV-infected cells and inhibited PEDV infection by activating the mitochondria-related caspase pathway. Furthermore, we used the inhibitors Z-DEVD-FMK and Pifithrin-α (PFT-α) to support our hypothesis. In conclusion, the TCRV-activated caspase pathway triggered early apoptosis of PEDV-infected cells, thereby inhibiting PEDV infections.

Successful Eradication of Porcine Epidemic Diarrhea in an Enzootically Infected Farm: A Two-Year Follow-Up Study

Porcine epidemic diarrhea virus (PEDV) has negatively affected the welfare of animals and their productivity in South Korea for three decades. A shortage of effective control measures has led to the virus becoming endemic in domestic pig populations. This study aimed to describe how our intervention measures were implemented for PEDV elimination in an enzootically infected farm. We operated a risk assessment model of PEDV recurrence to obtain information about the virus itself, herd immunity, virus circulation, and biosecurity at the farm. Next, we conducted a four-pillar-based two-track strategy to heighten sow immunity and eradicate the virus, with longitudinal monitoring of immunity and virus circulation, involving strict biosecurity, prime-boost pre-farrow L/K/K immunization, all-in-all-out and disinfection practices in farrowing houses, and disinfection and gilt management in wean-to-finish barns. In particular, we observed a high prevalence and long-term survival of PEDV in slurries, posing a critical challenge to PED eradication and highlighting the necessity for consecutive testing of barn slurry samples and for the management of infected manure to control PEDV. Genetic analysis of PEDVs in this farm indicated that genetic drift continued in the spike gene, with a substitution rate of 1.683 × 10⁻⁴ substitutions/site/year. Our study underlines the need for active monitoring and surveillance of PEDV in herds and their environments, along with the coordinated means, to eliminate the virus and maintain a negative herd. The tools described in this study will serve as a framework for regional and national PED eradication programs.