The enteric disease of swine recognized in the early 1970s in Europe was initially described as "epidemic viral diarrhea" and is now termed "porcine epidemic diarrhea (PED)". The coronavirus referred ...to as PED virus (PEDV) was determined to be the etiologic agent of this disease in the late 1970s. Since then the disease has been reported in Europe and Asia, but the most severe outbreaks have occurred predominantly in Asian swine-producing countries. Most recently, PED first emerged in early 2013 in the United States that caused high morbidity and mortality associated with PED, remarkably affecting US pig production, and spread further to Canada and Mexico. Soon thereafter, large-scale PED epidemics recurred through the pork industry in South Korea, Japan, and Taiwan. These recent outbreaks and global re-emergence of PED require urgent attention and deeper understanding of PEDV biology and pathogenic mechanisms. This paper highlights the current knowledge of molecular epidemiology, diagnosis, and pathogenesis of PEDV, as well as prevention and control measures against PEDV infection. More information about the virus and the disease is still necessary for the development of effective vaccines and control strategies. It is hoped that this review will stimulate further basic and applied studies and encourage collaboration among producers, researchers, and swine veterinarians to provide answers that improve our understanding of PEDV and PED in an effort to eliminate this economically significant viral disease, which emerged or re-emerged worldwide.
Based on the discrete model of infection spread in a closed population, appearance of epidemic waves associated with strengthening and weakening quarantine measures in the present paper is shown. The ...effect of quarantine measures is considered in the model under consideration via time dependence in the infection transmission rate. It was shown that the epidemic development is controlled by four key parameters: the number of infected persons, the average virus carriage time (as applied to COVID-19-type epidemics caused by the virus SARS-CoV-2 spread), the average number of dangerous contacts (which can cause virus transfer from an infected person to healthy men) of one infectious person (virus carrier) per day and the probability of infection due to a hazardous contact. The two latter parameters enter the model only as a product called the indicator of infection growth (IG) in population. The found solutions depend also on the population size and on the initial number of infected persons. The IG in the model under consideration is similar in meaning to the reproductive number in continuous SIR and SEIR models. At the same time, due to the prolonged virus carriage characteristic of COVID-19, the solutions proposed here are based on the equations with delay, and even without temporal variations of the IG, differ significantly from the SIR and SEIR models. The effect of the feedback between the epidemic spread rate and variations in the IG, caused by strengthening or weakening quarantine measures is studied. It results in a principal change in the epidemic behavior, which not reaching the saturation mode, transforms to its wavy flow mode. The dependence of the onset of epidemic waves on characteristic times of quarantine restriction weakening was revealed. In the model under consideration, the possibility of complete epidemic end in the case of long-term restricted quarantine measures was shown. The possible existence of the quasi-steady mode of low-intensity epidemic was detected. In this mode, the number of virus carriers remains unchanged for a long time due to the balance of the number of infections and recoveries per day.
•Based on the discrete model of infection spread in a closed population, appearance of epidemic waves associated with strengthening and weakening quarantine measures was shown. The effect of quarantine measures is considered in the model under consideration via time dependence in the infection transmission rate.•The epidemic development is controlled by the parameters: the number of infected persons, the average virus carriage time, the average number of dangerous contacts of one virus carrier per day and the probability of infection due to a hazardous contact.•The found solutions depend also on the population size and on the initial number of infected persons. The infection growth parameter IG in the model under consideration is similar in meaning to the reproductive number in continuous SIR and SEIR models. At the same time, due to the prolonged virus carriage characteristic of COVID-19, the solutions proposed here are based on the equations with delay, and even without temporal variations of the IG, differ significantly from the SIR and SEIR models.•The effect of the feedback between the epidemic spread rate and variations in the IG, caused by strengthening or weakening quarantine measures is studied. It results in a principal change in the epidemic behavior, which not reaching the saturation mode, transforms to its wavy flow mode. In the model under consideration, the possibility of complete epidemic end in the case of long-term restricted quarantine measures was shown.•The possible existence of the quasi-steady mode of low-intensity epidemic was detected. In this mode, the number of virus carriers remains unchanged for a long time due to the balance of the number of infections and recoveries per day.
Porcine epidemic diarrhea virus (PEDV) is a coronavirus that infects cells lining the small intestine of swine, resulting in vomiting, diarrhea, and dehydration. The amino acid sequence of the spike ...(S) protein, which is the principal target recognized by host immune cells, has multiple mutations that distinguish the two PEDV genotypes, G1 and G2. To determine whether these mutations lead to changes in antigenicity, as suggested by the failure of PEDV vaccines in China, we first optimized the codons of typical S genes of the CV777 vaccine strain (G1 subtype) and LNCT2 strain (G2 subtype) and expressed the recombinant full-length sequence of the S protein in a eukaryotic expression system. The IgG antibody levels of serum from mice immunized with purified S protein were markedly high. Antigenicity was compared by detection of polyclonal antibodies (PAbs) against the virus and S protein using an enzyme-linked immunosorbent assay (ELISA), an indirect immunofluorescence assay (IFA), and a serum cross-neutralization (SN) assay. Reactivity with the PAbs revealed significant cross-reactivity between the two PEDV subtypes, although there was a twofold difference in the antigenic responses based on PAb titers in the ELISA and IFA. Consistent with the variation in the S gene sequences, the SN titer suggested differences in the neutralization activity of the S protein between the two subtypes, which could explain the antigenic variation between the PEDV subtypes G1 and G2.
Abstract Porcine epidemic diarrhea virus (PEDV) has two genotypes, G1 and G2. To research the immunogenicity differences of PEDV G1 and G2 genotype strains and obtain a neutralizing monoclonal ...antibody (mAb), we inoculated specific-pathogen-free BALB/c mice with a newly emerged strain, PEDV-LNCT2. After immunizations, cells from the spleen of the mice were fused with SP2/0 myeloma cells. Following culturing and subcloning, a strain, 1B9, secreting neutralizing antibody, was obtained. The 1B9 mAb neutralized new variant genotype 2 PEDV strains (LNCT2, LNSY, and Hjms), but it did not neutralize a genotype 1 PEDV strain (CV777), in vitro . Results showed that the epitope recognized by the 1B9 mAb lies in the spike protein, and that it is a conformational epitope. These findings confirm that allelic differences in the PEDV S gene between the G1 and G2 genotype strains led to changes in the S protein and, thus, differences in its immunogenicity.
Acute diarrhea outbreaks caused by porcine epidemic diarrhea virus (PEDV) have been observed in various pig-breeding provinces of China since December 2010. Endemic strains of PEDV were isolated from ...different areas, and the complete genome sequences of 10 isolates were determined. Our objective in this study was to genetically characterize current Chinese field isolates of PEDV to better understand their epidemiology and genetic diversity. Sequence analysis showed that 10 post-2010 isolates shared high homology with each other and were always clustered together with the virulent DR13 strains (South Korea) and/or one earlier Chinese strain, CH-S, in phylogenetic analysis. All post-2010 isolates possessed common sequence changes in each gene. Our results suggest that current Chinese PEDV isolates originated from either South Korean and/or Chinese ancestors that underwent some genetic variation, thereby forming a new PEDV genotype in China.
In this paper, we propose new mathematical models with nonlinear incidence rate and double epidemic hypothesis. Then we dedicate to develop a method to obtain the threshold of the stochastic SIS ...epidemic model. To this end, first, we investigate the stability of the equilibria of the deterministic system and obtain the conditions for the extinction and the permanence of two epidemic diseases. Second, we explore and obtain the threshold of a stochastic SIS system for the extinction and the permanence in mean of two epidemic diseases. The results show that a large stochastic disturbance can cause infectious diseases to go to extinction, in other words, the persistent infectious disease of a deterministic system can become extinct due to the white noise stochastic disturbance. This implies that the stochastic disturbance is conducive to epidemic diseases control. To illustrate the performance of the theoretical results, we present a series of numerical simulations of these cases with respect to different noise disturbance coefficients.
Chronic lower airway infection with
is a major contributor to morbidity and mortality in individuals suffering from the genetic disease cystic fibrosis (CF). Whereas it was long presumed that each ...patient independently acquired unique strains of
present in their living environment, multiple studies have since demonstrated that shared strains of
exist among individuals with CF. Many of these shared strains, often referred to as clonal or epidemic strains, can be transmitted from one CF individual to another, potentially reaching epidemic status. Numerous epidemic
strains have been described from different parts of the world and are often associated with an antibiotic-resistant phenotype. Importantly, infection with these strains often portends a worse prognosis than for infection with nonclonal strains, including an increased pulmonary exacerbation rate, exaggerated lung function decline, and progression to end-stage lung disease. This review describes the global epidemiology of clonal
strains in CF and summarizes the current literature regarding the underlying biology and clinical impact of globally important CF clones. Mechanisms associated with patient-to-patient transmission are discussed, and best-evidence practices to prevent infections are highlighted. Preventing new infections with epidemic
strains is of paramount importance in mitigating CF disease progression.
Simple phenomenological growth models can be useful for estimating transmission parameters and forecasting epidemic trajectories. However, most existing phenomenological growth models only support ...single-peak outbreak dynamics whereas real epidemics often display more complex transmission trajectories.
We develop and apply a novel sub-epidemic modeling framework that supports a diversity of epidemic trajectories including stable incidence patterns with sustained or damped oscillations to better understand and forecast epidemic outbreaks. We describe how to forecast an epidemic based on the premise that the observed coarse-scale incidence can be decomposed into overlapping sub-epidemics at finer scales. We evaluate our modeling framework using three outbreak datasets: Severe Acute Respiratory Syndrome (SARS) in Singapore, plague in Madagascar, and the ongoing Ebola outbreak in the Democratic Republic of Congo (DRC) and four performance metrics.
The sub-epidemic wave model outperforms simpler growth models in short-term forecasts based on performance metrics that account for the uncertainty of the predictions namely the mean interval score (MIS) and the coverage of the 95% prediction interval. For example, we demonstrate how the sub-epidemic wave model successfully captures the 2-peak pattern of the SARS outbreak in Singapore. Moreover, in short-term sequential forecasts, the sub-epidemic model was able to forecast the second surge in case incidence for this outbreak, which was not possible using the simple growth models. Furthermore, our findings support the view that the national incidence curve of the Ebola epidemic in DRC follows a stable incidence pattern with periodic behavior that can be decomposed into overlapping sub-epidemics.
Our findings highlight how overlapping sub-epidemics can capture complex epidemic dynamics, including oscillatory behavior in the trajectory of the epidemic wave. This observation has significant implications for interpreting apparent noise in incidence data where the oscillations could be dismissed as a result of overdispersion, rather than an intrinsic part of the epidemic dynamics. Unless the oscillations are appropriately modeled, they could also give a false positive, or negative, impression of the impact from public health interventions. These preliminary results using sub-epidemic models can help guide future efforts to better understand the heterogenous spatial and social factors shaping sub-epidemic patterns for other infectious diseases.
Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus that causes acute watery diarrhea and vomiting in unweaned piglets, and is associated with high mortality, thus causing severe ...economic losses in the pig industry. Currently, although attenuated vaccines are commonly used in commercial pig farms in China, they do not completely protect against all mutated wild-type strains. Existing nucleic acid assays have high sensitivity and specificity, but the complexity of the assay process and expensive instrumentation hinder disease detection. Here, reverse transcription–enzymatic recombinase amplification (RT-ERA) was combined with the CRISPR-Cas12a system to develop a rapid diagnostic method to distinguish PEDV wild-type strains from attenuated vaccine strains. The protocol used crRNA and RT-ERA amplification primers against open reading frame 3 (ORF3), followed by Cas12a/crRNA complex detection of predefined target sequences at 37 °C for 30 min, thus producing results visible to the naked eye under LED blue light. The assay is highly sensitive and specific, detecting as few as two copies of the target gene per test and showing no cross-reactivity with other porcine pathogens. Overall, this integrated RT-ERA pre-amplification and Cas12a/crRNA cleavage assay is a practical tool for reliable and rapid detection of PEDV for diagnostic differentiation.
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