Porcine Epidemic Diarrhea Virus Outbreaks Research Articles

Longitudinal and Cross-Sectional Evaluation of Two Commercial Swine Breeding Herds to Characterize Neutralizing Antibody Levels following Porcine Epidemic Diarrhea Virus Outbreaks.

Neutralizing antibodies to Porcine Epidemic Diarrhea Virus (PEDV) can be detected by 3 weeks post-infection and remain detectable through at least 24 weeks post-infection. The objective of this study was to evaluate the levels of neutralizing antibodies in sow and piglet serum and sow milk to determine the duration of neutralizing antibodies following PEDV outbreaks. Two farms were selected for the study following outbreaks of PEDV. Monthly, cohorts of sows were sampled and followed through two farrowings. Following each farrowing, samples from piglets and milk were collected. Samples were evaluated for PEDV-neutralizing antibodies by a high-throughput fluorescent neutralization assay. Although neutralizing antibodies to PEDV can be detected throughout 15 months post-outbreak, a decrease in circulating neutralizing antibody levels is noted in farms beginning at six months post-outbreak. With decreasing levels, farms may become more vulnerable to PEDV outbreaks, and practitioners can focus on this time window to implement intervention strategies.

Effectiveness of gilt acclimatization - improvement procedures in a farm with recurrent outbreaks of porcine epidemic diarrhea.

Porcine epidemic diarrhea (PED) is a severe infectious disease that causes very high mortality in newborn piglets up to 2-3 weeks age. The main cause of repeated outbreaks of PED in infected farms is the continuing circulation of the PED virus (PEDV). Improper gilt management, including inappropriate gut feedback, commingling, and inadequate immunization, causes a prolonged virus circulation in breeding herds. Moreover, insufficient transfer of passive immunity through the colostrum to newborn piglets can also increase infection risk. Therefore, a gilt management program that controls infection should focus on infection monitoring and acclimatization. We investigated the source of recurrent PEDV outbreaks and examined how the effect of immunization methods, specifically using gut feedback mechanism and vaccination, can reduce PEDV circulation and improve immune responses in replacement gilts. The study site was a segregated commercial production farm with endemic PEDV. The acclimatization methods included gut feedback and vaccination. This longitudinal study evaluated two strategies of gilt acclimatization against PEDV: Program 1 (routine farm management) and Program 2 (early feedback program and all-in-all-out system). Levels of PED RNA in fecal samples were measured using quantitative reverse transcription-polymerase chain reaction, and the PEDV S gene was sequenced. Porcine epidemic diarrhea-specific immune responses were assessed using enzyme-linked immunosorbent assay and the serum neutralization test. Porcine epidemic diarrhea outbreaks occurred in the farrowing, nursery, and finishing units and farrowed litters 5-10 days old were symptomatic of PED. Phylogenetic analyses of the S gene showed PEDV sequence divergence between PEDV field strains and vaccine strain, which may contribute to periodic outbreaks and continued persistence of PEDV in the farm. After gut feedback and acclimatization, replacement gilts from Program 1 continued to shed PEDV before being introduced to sow herds, while those from Program 2 did not shed PEDV before being introduced to sow herds. However, the components of the immune response against PEDV in serum samples, including specific immunoglobulin (Ig)G, specific IgA, and neutralizing antibodies were lower in gilts of Program 2 than those in Program 1. We speculate that implementing the appropriate gilt acclimatization program can control PEDV circulation in farm. However, the acclimatization methods in Program 2 did not induce a strong and adequate immune response in replacement gilts. Therefore, maternal immunity levels and the degree of protection against PEDV require further study.

Correlation between the IgG/IgA Antibody Response against PEDV Structural Protein and Virus Neutralization.

Porcine epidemic diarrhea (PED) is a highly contagious intestinal infectious disease caused by porcine epidemic diarrhea virus (PEDV). Large-scale outbreaks of PEDV have caused huge economic losses to the pig industry since 2010. Neutralizing antibodies play a pivotal role in protecting piglets from enteric infections. However, there has been no systematic report on the correlations between neutralizing antibody titers (NTs) and absorbance values of IgG or IgA to all PEDV individual structural proteins in clinical serum, fecal, and colostrum samples. In this study, the spike protein S1 domain (S1), membrane protein (M), envelope protein (E), and nucleocapsid protein (N) of the variant PEDV strain AH2012/12 were expressed and purified by using the human embryonic kidney (HEK) 293F expression system. A total of 92 clinical serum samples, 46 fecal samples, and 33 colostrum samples were collected, and the correlations between IgG or IgA absorbance values and NTs were analyzed. R2 values revealed that anti-S1 IgA absorbance values show the highest agreement with NTs in all serum, fecal, and colostrum samples, followed by the N protein. The correlations between anti-E or M IgA and NTs were very low. However, in the colostrum samples, both IgG and IgA to S1 showed high correlations with NTs. In addition, compared with E and M, the highest correlations of IgA absorbance values were with N and S1 in serum and fecal samples. Overall, this study revealed the highest correlation between NTs and IgA to PEDV S1 protein. Therefore, the diagnostic method with anti-S1 IgA can be used as a powerful tool for assessing the immune status of pigs. IMPORTANCE The humoral immune response plays an important role in virus neutralization. Against PEDV, both IgG and the mucosal immune component IgA play roles in virus neutralization. However, which plays a more prominent role and whether there are differences in different tissue samples are not clearly reported. Additionally, the relationship between IgG and IgA against individual structural proteins and viral neutralization remains unclear. In this study, we systematically determined the relationship between IgG and IgA against all PEDV structural proteins and viral neutralization in different clinical samples and found the highest correlation between neutralization activity and IgA to PEDV S1 protein. Our data have important guiding implications in the evaluation of immune protection.

Modeling between-farm transmission dynamics of porcine epidemic diarrhea virus: Characterizing the dominant transmission routes

The role of transportation vehicles, pig movement between farms, proximity to infected premises, and feed deliveries has not been fully considered in the dissemination dynamics of porcine epidemic diarrhea virus (PEDV). This has limited efforts for disease prevention, control and elimination restricting the development of risk-based resource allocation to the most relevant modes of PEDV dissemination. Here, we modeled nine pathways of between-farm transmission represented by a contact network of pig movements between sites, farm-to-farm proximity (local transmission), four distinct contact networks of transportation vehicles (trucks that transport pigs from farm-to-farm and farm-to-markets, as well as trucks transporting feed and staff), the volume of animal by-products in feed diets (e.g., fat and meat-and-bone-meal) to reproduce PEDV transmission dynamics. The model was calibrated in space and time with weekly PEDV outbreaks. We investigated the model performance to identify outbreak locations and the contribution of each route in the dissemination of PEDV. The model estimated that 42.7% of the infections in sow farms were related to vehicles transporting feed, 34.5% of infected nurseries were associated with vehicles transporting pigs between farms, and for both farm types, local transmission or pig movements were the next most relevant transmission routes. On the other hand, finishers were most often (31.4%) infected via local transmission, followed by the vehicles transporting feed and pigs between farms. Feed ingredients did not significantly improve model calibration metrics, sensitivity, and specificity; therefore, it was considered to have a negligible contribution in the dissemination of PEDV. The proposed modeling framework provides an evaluation of PEDV transmission dynamics, ranking the most important routes of PEDV dissemination and granting the swine industry valuable information to focus efforts and resources on the most important transmission routes.

Chestnut inner shell extract inhibits viral entry of porcine epidemic diarrhea virus and other coronaviruses in vitro.

Porcine epidemic diarrhea virus (PEDV) is a coronavirus that causes acute diarrhea in suckling piglets. Although vaccines are able to reduce the incidence of PEDV infection, outbreaks of PEDV continue to be reported worldwide and cause serious economic losses in the swine industry. To identify novel antiviral sources, we identified the chestnut (Castanea crenata) inner shell (CIS) as a natural material with activity against PEDV infection in vitro. The ethanol fractions of CIS extracts potently inhibited PEDV infection with an IC90 of 30 μg/ml. Further investigation of the virus lifecycle demonstrated that CIS extract particularly targeted the early stages of PEDV infection by blocking viral attachment and membrane fusion at rates of 80~90%. In addition, CIS extract addition reduced the viral entry of other members of the Coronaviridae family. Our data demonstrated that CIS extract inhibited PEDV infection by blocking cell entry in vitro and suggest that CIS extract is a new prophylactic and therapeutic agent against PEDV and other coronavirus infections.

Environmental monitoring of porcine epidemic diarrhea virus within a swine farm during a disease outbreak

Environmental swabs were used as a monitoring tool during a porcine epidemic diarrhea virus outbreak at a farrow-to-finish swine facility. Samples were collected over the course of 16 weeks following initial infection, and changes in biosecurity practices were implemented based on results. Separation of on-farm areas into different zones as determined by animal and feed ingredient contact and proximity allowed for a targeted approach to clean-up efforts.

The New Porcine Epidemic Diarrhea Virus Outbreak May Mean That Existing Commercial Vaccines Are Not Enough to Fully Protect Against the Epidemic Strains.

Background: On October 30, 2020, piglets and sows in the farrowing house of a pig farm in Jiangxi showed clinical symptoms such as anorexia, watery diarrhea, and vomiting. Epidemiological test, clinical necropsy, and RT-PCR test were carried out on the pig farm for diagnosis. After comprehensive considerations, the disease was judged as porcine epidemic diarrhea virus infection.Results: Thereafter, a series of comprehensive prevention and control measures such as emergency vaccination with autogenous vaccines were adopted. Half a month after inoculation with autogenous vaccines for the farm, the mortality rate of newborn piglets in the farrowing house began to decline, and production gradually returned to being stable. The second-generation sequencing analysis and phylogenetic analysis showed that the porcine epidemic diarrhea virus (PEDV) sequence obtained from the stool and small intestine samples of the diseased pigs on the farm was 97.8% homologous to the vaccine strain. At the same time, antibody testing found that the vaccinated pigs on the pig farm had satisfactory immune response.Conclusion: This case indicated that the PEDV outbreak on the pig farm might aggravate owing to the strain being mutated and could escape the immune protection of the existing vaccine. This case has accumulated technical data for the clinical prevention and control of porcine epidemic diarrhea.

60 Use of environmental monitoring to inform biosecurity compliance in a swine health challenge

Abstract As endemic and foreign diseases threaten the U.S. swine herd, producers are scrutinizing on-farm biosecurity practices. Environmental monitoring may help inform biosecurity compliance. Unfortunately, the Kansas State Swine Teaching and Research Center suffered an outbreak of porcine epidemic diarrhea virus (PEDV) in March 2019. The objective of this research was to use environmental monitoring to evaluate biosecurity risk on a farm experiencing a viral outbreak. In a completely randomized design, environmental swabs were collected after barn sanitation on 14, 28, and 42-days after initial PEDV diagnosis from four zones: 1) pig contact surfaces within barns, 2) non-pig contact surfaces within barns, 3) outside barns and inside offices, and 4) transition areas. Swabs were analyzed for PEDV, rotavirus, and Enterobacteriaceae at a veterinary diagnostic laboratory. Data were analyzed using the GLIMMIX procedures of SAS, v 9.4 (Cary, NC). There was a significant time × zone interaction for PEDV (P < 0.0001), where swabs from non-pig contact areas within barns on d 28 (Zone 2) had greater (P < 0.05) levels of PEDV than pig-contact areas (Zone 1) on d 14, 28, or 42. No other interactions existed, and they were therefore removed from the statistical model. Time did not affect (P > 0.05) any measured response criteria. No PEDV was detected (45.0 Ct) from Zone 1 due to recent sanitation, but viral presence was highest (P < 0.05) in non-pig contact areas inside barns and was tracked outside of barns and through transition zones (32.9, 34.3, and 38.5 Ct for zones 2, 3, and 4, respectively). There was no detected difference (P > 0.05) for rotavirus or Enterobacteriaceae in time or zone. In conclusion, producers experiencing a PEDV outbreak may successfully decontaminate pig-contact surfaces, but still have risk throughout the farm. Biosecurity practices should support preventing cross-contamination from other contaminated areas.

Origin and epidemic status of porcine epidemic diarrhea virus variants in China.

From 2010, porcine epidemic diarrhea virus (PEDV) variants caused sequential outbreaks of disease in Asia and the United States. In this retrospective study, 49 complete spike (S) gene sequences were obtained from PEDV strains collected in China from 2014 to 2016. We observed that variant PEDV strains with novel insertions, deletions, and multiple S gene recombination types were present in China. In addition, mixed infections involving different variant strains were observed in some areas. Based on phylogenetic and recombination analyses, we determined that the newly emerged PEDV variants potentially originated via recombination between the earliest Chinese G1 genogroup strain, JS-2004-2 and earlier Korean pandemic strains. These findings provide important information for understanding ongoing PEDV outbreaks and suggest that novel variants make it more difficult to prevent PEDV infection.

Identifying outbreaks of Porcine Epidemic Diarrhea virus through animal movements and spatial neighborhoods

The spread of pathogens in swine populations is in part determined by movements of animals between farms. However, understanding additional characteristics that predict disease outbreaks and uncovering landscape factors related to between-farm spread are crucial steps toward risk mitigation. This study integrates animal movements with environmental risk factors to identify the occurrence of porcine epidemic diarrhea virus (PEDV) outbreaks. Using weekly farm-level incidence data from 332 sow farms, we applied machine-learning algorithms to quantify associations between risk factors and PEDV outbreaks with the ultimate goal of training predictive models and to identify the most important factors associated with PEDV occurrence. Our best algorithm was able to correctly predict whether an outbreak occurred during one-week periods with >80% accuracy. The most important predictors included pig movements into neighboring farms. Other important neighborhood attributes included hog density, environmental and weather factors such as vegetation, wind speed, temperature, and precipitation, and topographical features such as slope. Our neighborhood-based approach allowed us to simultaneously capture disease risks associated with long-distance animal movement as well as local spatial dynamics. The model presented here forms the foundation for near real-time disease mapping and will advance disease surveillance and control for endemic swine pathogens in the United States.

An alternative pathway of enteric PEDV dissemination from nasal cavity to intestinal mucosa in swine

Porcine epidemic diarrhea virus (PEDV) has catastrophic impacts on the global pig industry. Although the fecal–oral route is generally accepted, an increased number of reports indicate that airborne transmission may contribute to PEDV outbreak. Here, we show that PEDV could cause typical diarrhea in piglets through a nasal spray. Firstly, PEDV can develop a transient nasal epithelium infection. Subsequently, PEDV-carrying dendritic cells (DCs) allow the virus to be transferred to CD3+ T cells via the virological synapse. Finally, virus-loaded CD3+ T cells reach the intestine through the blood circulation, leading to intestinal infection via cell-to-cell contact. Our study provides evidence for airborne transmission of a gastrointestinal infected coronavirus and illustrates the mechanism of its transport from the entry site to the pathogenic site.

Evolutionary and genotypic analyses of global porcine epidemic diarrhea virus strains.

Porcine epidemic diarrhea virus (PEDV), which re‐emerged in China in October 2010, has spread rapidly worldwide. Detailed analyses of the complete genomes of different PEDV strains are essential to understand the relationships among re‐emerging and historic strains worldwide. Here, we analysed the complete genomes of 409 strains from different countries, which were classified into five subgroup strains (i.e., GI‐a, GI‐b, GII‐a, GII‐b, and GII‐c). Phylogenetic study of different genes in the PEDV strains revealed that the newly discovered subgroup GII‐c exhibited inconsistent topologies between the spike gene and other genes. Furthermore, recombination analysis indicated that GII‐c viruses evolved from a recombinant virus that acquired the 5′ part of the spike gene from the GI‐a subgroup and the remaining genomic regions from the GII‐a subgroup. Molecular clock analysis showed that divergence of the GII‐c subgroup spike gene occurred in April 2010, suggesting that the subgroup originated from recombination events before the PEDV re‐emergence outbreaks. Interestingly, Ascaris suum, a large roundworm occurring in pigs, was found to be an unusual PEDV host, providing potential support for cross‐host transmission. This study has significant implications for understanding ongoing global PEDV outbreaks and will guide future efforts to develop effective preventative measures against PEDV.

Porcine epidemic diarrhea vaccine evaluation using a newly isolated strain from Korea

Porcine epidemic diarrhea virus (PEDV) infects pigs and causes an enteric disease that is characterized by vomiting and watery diarrhea. PEDV outbreaks have a tremendous financial impact on the worldwide pork industry. In South Korea, the incidence of PEDV has continued despite nationwide use of attenuated and inactivated vaccines, raising questions regarding the current vaccines’ efficacy and the need for new vaccine development. In the present study, we isolated a new Korean PEDV epidemic strain, PED-CUP-B2014, in Vero cells. Phylogenetic analysis of the spike gene demonstrated that the PED-CUP-B2014 belongs in genogroup G2b and is close to PEDVs currently circulating in many countries including the United States, and is distinct from many current vaccine strains. Upon serial passages into Vero cells, PED-CUP-B2014 adapted to Vero cells, which was evidenced as higher virus growth in Vero cells and confirmed lower virulence in suckling piglets. The administration of the inactivated 65-passaged PED-CUP-B2014 to sows greatly increased the survival rate of their offspring and significantly reduced diarrhea severity after PEDV challenge. Higher serum/colostrum PEDV-specific antibodies and higher neutralizing titers were shown in sows vaccinated with PED-CUP-B2014 compared to unvaccinated sows or sows administered commercial PEDV vaccine. Altogether, our data demonstrated that the newly isolated PEDV strain conferred critical passive immune protection to pigs against epidemic PEDV infection.

Porcine epidemic diarrhea virus (PEDV) introduction into a naive Dutch pig population in 2014

Porcine epidemic diarrhea virus (PEDV) is the highly contagious, causative agent of an economically important acute enteric disease in pigs of all ages. The disease is characterized by diarrhea and dehydration causing mortality and growth retardation. In the last few decades, only classical PEDV was reported sporadically in Europe, but in 2014 outbreaks of PEDV were described in Germany. Phylogenetic analysis showed a very high nucleotide similarity with a variant of PEDV that was isolated in the US in January 2014. The epidemiological situation of PEDV infections in the Netherlands in 2014 was unknown and a seroprevalence study in swine was performed. In total, 838 blood samples from sows from 267 farms and 101 samples from wild boars were collected from May till November 2014 and tested for antibodies against PEDV by ELISA. The apparent herd prevalence of 0.75% suggests that PEDV was not circulating on a large scale in the Netherlands at this time. However, in November 2014 a clinical outbreak of PEDV was diagnosed in a fattener farm by PCR testing. This was the first confirmed PEDV outbreak since the early nineties. Sequence analyses showed that the viruses isolated in 2014 and 2015 in the Netherlands cluster with recently found European G1b strains. This suggests a one event introduction of PEDV G1b strains in Europe in 2014, which made the Netherlands and other European countries endemic for this type of strains since then.

Characterization of acute-phase proteins associated with a porcine epidemic diarrhea virus outbreak in suckling piglets and sows in Mexico

The objective of this study was to determine the relationships between four acute phase proteins (APP), and the pathological effects of porcine epidemic diarrhea virus (PEDV) in piglets and sows. Virus detection was done in laboratory (PCR method) with feces samples. Blood samples were obtained from lactating sows and piglets that survived the first day of life according to the presence or absence of characteristic enteric signs (ES) of the disease: vomiting and diarrhea. (I) Neonatal piglets without ES (n=7), (II) Neonatal piglets with ES (n=8), (III) Sows without ES (n=6), and (IV) Sows with ES (n=6). To determine the APP concentration in blood, serum amyloid A (SAA) and haptoglobin (HAP) were determined by a non-species-specific commercial ELISA assay. C-reactive protein (CRP) and PIGMAP serum levels were quantified by monoclonal antibody sandwich ELISA assay. Finally, no significant differences (P>0.05) were found in serum concentrations of different APP between piglets and sows with and without ES. Piglet survival is linked by the degree of dehydration during diarrhea; PEDV causes ES quickly and severely before of the induction of pro-inflammatory cytokines, but this pathological synthesis still remains unclear.

A novel duplex TaqMan probe-based real-time RT-qPCR for detecting and differentiating classical and variant porcine epidemic diarrhea viruses

Two different genotypes of porcine epidemic diarrhea virus (PEDV), the classical and variant strains, are classified by multiple insertions and deletions in their S genes. It is critical to detect and differentiate two genotypes in the pork industry to prevent PEDV outbreaks. In the present study, a novel duplex TaqMan RT-PCR was developed for detecting and differentiating PEDV strains in China. There was no cross-amplification between the two probes when using standard recombinant plasmids, and the specificity was further confirmed by using other seven non-PEDV swine pathogens. The minimum copies required for the detection of both classical and variant PEDV were 4.8 × 102 DNA copies/reaction. The repeatability of TaqMan RT-PCR was evaluated using standard recombinant plasmids and gave coefficients of variation 0.19–4.93. In recent 5 years, 79 clinical samples were collected from piglets with severe diarrhea in the Central China. Among these clinical samples, 51 were confirmed as PEDV positive by conventional RT-PCR, whereas 63 variant PEDV, 3 co-infections and 1 classical PEDV were confirmed by this duplex TaqMan RT-PCR, with viral loads of 102–108, 102–103, and 104 copies/reaction, respectively. Therefore, the duplex TaqMan RT-PCR could be a useful method for detecting and differentiating variant and classical PEDV strains. The results showed that variant PEDV was prevalent in clinical samples in central China. Moreover, in this study, co-infection by PEDV strains was detected for the first time and might help explain the emergence of the novel recombinant PEDV in recent years.

Understanding the early dynamics of the 2014 porcine epidemic diarrhea virus (PEDV) outbreak in Ontario using the incidence decay and exponential adjustment (IDEA) model.

BackgroundThe United States swine industry was first confronted with porcine epidemic diarrhea virus (PEDV) in 2013. In young pigs, the virus is highly pathogenic and the associated morbidity and mortality has a significant negative impact on the swine industry. We have applied the IDEA model to better understand the 2014 PEDV outbreak in Ontario, Canada. Using our simple, 2-parameter IDEA model, we have evaluated the early epidemic dynamics of PEDV on Ontario swine farms.ResultsWe estimated the best-fit R0 and control parameter (d) for the between farm transmission component of the outbreak by fitting the model to publically available cumulative incidence data. We used maximum likelihood to compare model fit estimates for different combinations of the R0 and d parameters. Using our initial findings from the iterative fitting procedure, we projected the time course of the epidemic using only a subset of the early epidemic data. The IDEA model projections showed excellent agreement with the observed data based on a 7-day generation time estimate. The best-fit estimate for R0 was 1.87 (95% CI: 1.52 – 2.34) and for the control parameter (d) was 0.059 (95% CI: 0.022 – 0.117). Using data from the first three generations of the outbreak, our iterative fitting procedure suggests that R0 and d had stabilized sufficiently to project the time course of the outbreak with reasonable accuracy.ConclusionsThe emergence and spread of PEDV represents an important agricultural emergency. The virus presents a significant ongoing threat to the Canadian swine industry. Developing an understanding of the important epidemiological characteristics and disease transmission dynamics of a novel pathogen such as PEDV is critical for helping to guide the implementation of effective, efficient, and economically feasible disease control and prevention strategies that are able to help decrease the impact of an outbreak.

Spray dried plasma as an alternative to antibiotics in piglet feeds, mode of action and biosafety.

The use of growth promoting and therapeutic antibiotics in piglet feed has been a concerning subject over the last few decades because of the risk of generating antimicrobial resistance that could be transferred to humans. As a result, many products have been proposed as potential alternatives to the use of antibiotics, and among these, spray dried plasma is considered one of the most promising. However, there have been concerns about its biosafety, particularly during periods of emergence or re-emergence of swine diseases in different regions of the world, such as the recent porcine epidemic diarrhea virus outbreak in North America. The objectives of this paper are to review recent publications about the use of spray dried plasma as an alternative to antibiotics in weaned pig diets, the possible mechanisms of action of spray dried plasma, and the existing evidence related to the biosafety of spray dried animal plasma. Particular attention is given to studies in which spray dried plasma has been directly compared to antibiotics or other alternative antimicrobial products. Several studies on the possible modes of action for spray dried plasma, such as preservation of gut barrier function or modulation of the immune response, are also reviewed. Finally, the paper focuses on the review of the existing studies on the risks of disease transmission with the use of spray dried plasma from porcine origin. Overall, spray dried plasma is a promising alternative to in-feed antimicrobials for piglets, particularly during the early stages of the post-weaning phase. Additionally, there is enough evidence to support that commercial spray dried porcine plasma is a safe product for pigs.

Evaluation of two singleplex reverse transcription-Insulated isothermal PCR tests and a duplex real-time RT-PCR test for the detection of porcine epidemic diarrhea virus and porcine deltacoronavirus

Recent outbreaks of porcine epidemic diarrhea virus (PEDV) and porcine deltacoronavirus (PDCoV) in multiple countries have caused significant economic losses and remain a serious challenge to the swine industry. Rapid diagnosis is critical for the implementation of efficient control strategies before and during PEDV and PDCoV outbreaks. Insulated isothermal PCR (iiPCR) on the portable POCKIT™ device is user friendly for on-site pathogen detection. In the present study, a singleplex PEDV RT-iiPCR, a singleplex PDCoV RT-iiPCR, and a duplex PEDV/PDCoV real-time RT-PCR (rRT-PCR) commercial reagents targeting the M gene were compared to an N gene-based PEDV rRT-PCR and an M gene-based PDCoV rRT-PCR that were previously published and used as reference PCRs. All PCR assays were highly specific and did not cross react with other porcine enteric pathogens. Analytical sensitivities of the PEDV RT-iiPCR, PDCoV RT-iiPCR and duplex PEDV/PDCoV rRT-PCR were determined using in vitro transcribed RNA as well as viral RNA extracted from ten-fold serial dilutions of PEDV and PDCoV cell culture isolates. Performance of each PCR assay was further evaluated using 170 clinical samples (86 fecal swabs, 24 feces, 19 intestines, and 41 oral fluids). Compared to the reference PEDV rRT-PCR, the sensitivity, specificity and accuracy of the PEDV RT-iiPCR were 97.73%, 98.78%, and 98.24%, respectively, and those of the duplex PEDV/PDCoV rRT-PCR were 98.86%, 96.34%, and 97.65%, respectively. Compared to the reference PDCoV rRT-PCR, the sensitivity, specificity and accuracy of the PDCoV RT-iiPCR were 100%, 100%, and 100%, respectively, and those of the PEDV/PDCoV duplex rRT-PCR were 96.34%, 100%, and 98.24%, respectively. Overall, all three new PCR assays were comparable to the reference rRT-PCRs for detection of PEDV and/or PDCoV. The PEDV and PDCoV RT-iiPCRs are potentially useful tools for on-site detection and the duplex PEDV/PDCoV rRT-PCR provides a convenient method to simultaneously detect the two viruses and differentiate PEDV from PDCoV.

Impact of Mated Female Nonproductive Days in Breeding Herd after Porcine Epidemic Diarrhea Virus Outbreak.

Porcine epidemic diarrhea virus (PEDV) is an important pathogen that has a significant economic impact on the swine industry by imposing a high rate of mortality in suckling piglets. However, limited information on the productivity values of gilts and sows infected with PEDV is available. Here, we evaluate the productivity index in gilts and sows during the 1-year period before (19 January 2013 to 18 January 2014) and after (19 January 2014 to 18 January 2015) a PEDV outbreak from a 2000-sow breeding herd in Taiwan. The farrowing rate (FR), return rate (RR), total pigs born per litter (TB), pigs born alive per litter (BA), weaning pigs per litter (WPL), pre-weaning mortality, percentage of sows mated by 7 days after weaning, weaning to first service interval (WFSI), mated female nonproductive days (NPDs), replacement rate of sows and sow culling rate were compared using productive records. The FR (-9.6%), RR (+9.8%), TB (-1.6), BA (-1.1), WPL (-1.1), sows mated by 7 days after weaning (-6.9%), WFSI (+0.8 days), NPDs (+6.9 days) and sow culling rate (+7.2%) were significantly different between the 1-year pre-PEDV outbreak period and the post-PEDV outbreak period. Impacts of the PEDV infection on the reproductive performance were more severe in pregnant gilts than in sows. In conclusion, these findings indicate that the outbreak of PEDV caused an increase in the rate of NPDs in breeding herds.