The efficacy of a modified live virus vaccine Fostera® PRRS against heterologous strains of porcine reproductive and respiratory syndrome virus: A meta-analysis.

Porcine reproductive and respiratory syndrome virus (PRRSV) is currently one of the most economically important health challenges in the global swine industry. The primary aim of this study was to evaluate the overall efficacy of a modified live virus vaccine Fostera® PRRS (F-PRRS) compared to no vaccination as reported in published studies, using meta-analytic techniques. Additionally, we aimed to evaluate the potential impact of age at vaccination and F-PRRS cross-protection against different genetically distanced PRRS strains. In total, 20 papers fulfilled the predefined inclusion criteria. Vaccinated pigs had on average 38.52 g/d higher daily weight gain and a 65% lower mortality (relative risk = 0.35) compared to non-vaccinates. F-PRRS reduced the maximum macroscopic lung lesion score on average by 16.82% points and the maximum viral load in serum by 1.36 log10 PRRSV RNA copies. Vaccination at 1 day and 21 days of age was similarly effective, and the pathogenic PRRS strain(s) used for challenge or being endemic in field studies (PRRSV-1, PRRSV-2, or PRRSV-1 & -2) did not significantly influence the outcomes. Our findings confirm the effectiveness of F-PRRS against heterologous PRRSV infection.

A comparison of three sampling approaches for detecting PRRSV in suckling piglets.

Determining whether porcine reproductive and respiratory syndrome virus (PRRSV) is circulating within a breeding herd is a longstanding surveillance challenge. Most commonly, piglets in farrowing rooms are sampled to infer the PRRSV status of the sow herd, with sample size based on the expectation of hypergeometric distribution and piglet selection based on simple random sampling (SRS), i.e., randomly selecting individuals from a population in a manner that all individuals have equal chance of being selected. Conceptually straightforward, the assumptions upon which it is based (homogeneous population and independence of individuals) rarely hold in modern swine facilities. Alternative approaches for sample selection include two-stage stratified sampling (2SS), i.e., randomly selecting litters (first stratum) and randomly selecting piglets (second stratum) within selected litters, and risk-based sampling (RBS), i.e., selecting litters with a higher risk of having viremic piglets, and randomly selecting pigs within those litters. The objectives of this study were to 1) characterize the pattern of distribution of PRRSV-viremic piglets in farrowing rooms and 2) compare the efficiency of SRS, 2SS, and RBS for the detection of PRRSV-viremic piglets. In 12 sow farms, serum samples were collected from all 4510 piglets in 422 litters housed in 23 farrowing rooms and tested for PRRSV RNA. At the population level, the distribution of PRRSV-viremic pigs was analyzed for population homogeneity and spatial clustering. At the litter level, litter size and sow parity were evaluated as risk factors. A non-homogeneous distribution of PRRSV-viremic piglets was observed in nearly all farrowing rooms (15/16), and spatial clustering detected on 11 occasions (11/16). Simulated sampling based on farrowing room data determined that 2SS required 1-to-25 fewer samples than SRS to detect ≥ 1 viremic piglet in 13 of 16 rooms and the same number of samples in 3 rooms. RBS required 1-to-7 fewer samples than 2SS to detect ≥ 1 viremic piglet in 7 of 16 rooms, the same number of samples in 6 rooms, and 1 more sample in 3 rooms. Notably, SRS was less efficient than either 2SS or RBS in detecting PRRSV-viremic piglets in farrowing rooms, regardless of the confidence level. It may be concluded that the core assumptions upon which most current surveillance methods are based do not hold in modern farrowing room facilities. Simulation-based sample size tables for SRS and 2SS are provided.

Finding PRRSV in sow herds: Family oral fluids vs. serum samples from due-to-wean pigs.

The aim of this study was to compare the detection of porcine reproductive and respiratory syndrome virus (PRRSV) in due-to-wean litters in commercial swine breeding herds using family oral fluids (FOF) vs. individual piglet serum samples. FOF and piglet serum samples were collected in 199 due-to-wean litters on six farms containing 2177 piglets. All samples were individually tested for PRRSV RNA by RT-rtPCR. A litter was considered PRRSV-positive when PRRSV RNA was detected in ≥ 1 piglet serum sample or the FOF sample. Mixed effect logistic regression with farm as a random effect was used 1) to evaluate the probability of obtaining a PRRSV RNA positive FOF as a function of the proportion of viremic piglets in a litter and 2) the effect of litter size and parity on the probability that a litter would test PRRSV RNA positive in FOF. A Bayesian prevalence estimation under misclassification (BayesPEM) analysis was used to calculate the PRRSV prevalence and 95 % credible interval given the condition that all samples (FOF and serum) tested negative. In total, 34 of 199 litters (17.1 %) contained ≥ 1 viremic piglet(s), and 28 of 199 litters (14.1 %) were FOF positive. When all piglet serum samples within a litter tested negative, 1 of 165 FOF (0.6 %) tested PRRSV RNA positive. The probability of a PCR-positive FOF sample from litters with 10 %, 20 %, 30 %, 40 %, and 50 % within-litter PRRSV prevalence was 3.5 %, 35.1 %, 88.8 %, 99.2 %, and >99.9 %, respectively. The odds of a PCR-positive FOF in a first parity litter were 3.36 times (95 % CI: 2.10-5.38) that of a parity ≥ 2 litter. The odds of a positive FOF result in a litter with ≤ 11 piglets were 9.90 times (95 % CI: 4.62-21.22) that of a litter with > 11 piglets. FOF was shown to be an efficacious sample type for PRRSV detection in farrowing rooms. A risk-based approach for litter selection combined with FOF collection can be used to improve on-farm PRRSV detection with a limited sample size, compared to sampling multiple individual pigs. Finally, the BayesPEM analysis showed that PRRSV may still be present in breeding herds when all samples (serum and FOF) test PRRSV RNA negative, i.e., negative surveillance results should be interpreted with caution.

Lung consolidation caused by Mycoplasma hyopneumoniae has a negative effect on productive performance and economic revenue in finishing pigs.

This study aimed to measure the impact of productivity and the consequent economic losses related to lung lesions caused by M. hyopneumoniae. Five-hundred 75 days-old pigs were selected and weighed at the beginning and at the end of the finishing phase to assess the average daily gain (ADG). These animals were evaluated at the slaughter, and samples were collected for laboratory analysis to confirm the presence of M. hyopneumoniae DNA. The lungs of each pig were examined and classified into groups based on the extension of macroscopic lung lesions. Four-hundred eighty-six lungs were examined and 68.5% (n = 333) had macroscopic lung lesions. All pigs with lesions were positive for M. hyopneumoniae in qPCR. Linear mixed regression models (proc Glimmix) were performed on SAS to estimate the effect of macroscopic lung lesion scores on the ADG of finishing pigs. All pairwise comparisons among lesion score groups were performed using p < 0.05. For each increase of one percent in the lesion area, there was a decrease of 1.8 g in the daily weight gain. All the groups had a numerically lower ADG when compared to Group 1 (no lesions). The economic analysis was performed by simulation on Excel to estimate and compare the financial performance of the different lung lesion score groups. The negative correlation found between the group with no lung lesions and the group with more than 15.1% of lesions, showed a statistical difference in ADG, which could mean an opportunity to gain up to $ 6.55 per pig at slaughter. The presence of lesions causes the animals to decrease their productive potential, causing financial loss and generating impacts on the production system.

Vaginal microbiota diverges in sows with low and high reproductive performance after porcine reproductive and respiratory syndrome vaccination.

Previous studies have demonstrated evidence for a relationship between the vaginal microbiome and reproductive performance, suggesting the vaginal microbiota may serve as a tool to predict farrowing outcomes in commercial pigs. In this study, we compared the vaginal microbiome in sows with low and high farrowing performance and used it to classify animals with contrasting reproductive outcomes in commercial sows following immune challenge with porcine respiratory and reproductive syndrome (PRRS) vaccination. Eighteen microbes were differentially abundant (q-value < 0.05) between the Low and High farrowing performance groups. Among them, Campylobacter, Bacteroides, Porphyromonas, Lachnospiraceae unclassified, Prevotella, and Phascolarctobacterium were also selected in the discriminant and linear regression analyses, and could be used as potential biomarkers for reproductive outcomes. The correct classification rate in the two groups was 100%. In conclusion, this study demonstrates that vaginal microbiota collected after PRRS vaccination could be potentially used to classify sows into having low or high farrowing performance in commercial herds.

Collecting oral fluid samples from due-to-wean litters.

Oral fluids are a common diagnostic sample in group-housed nursery, grow-finish, and adult swine. Although oral fluids from due-to-wean litters could be a valuable tool in monitoring pathogens and predicting the health status of pig populations post-weaning, it is generally not done because of inconsistent success in sample collection. The objective of this study was to determine the optimum procedure for collecting oral fluid samples from due-to-wean litters. Successful collection of oral fluids from due-to-wean litters using "Litter Oral Fluid" (LOF) or "Family Oral Fluid" (FOF) sampling techniques were compared in 4 phases involving 920 attempts to collect oral fluids. Phase 1 testing showed that prior exposure to a rope improved the success rates of both LOF (33.4%) and FOF (16.4%) techniques. Phase 2 determined that longer access to the rope (4 h vs 30 min) did not improve the success rate for either LOF or FOF. Phase 3 evaluated the effect of attractants and found that one (Baby Pig Restart®) improved the success rate when used with the FOF technique. Phase 4 compared the success rates of "optimized LOF" (litters previously trained) vs "optimized FOF" (litter previously trained and rope treated with Baby Pig Restart®) vs standard FOF. No difference was found between the FOF-based techniques, but both were superior to the "optimized LOF" technique. Thus, FOF-based procedures provided a significantly higher probability of collecting oral fluids from due-to-wean litters (mean success rate 84.9%, range 70% to 92%) when compared to LOF-based methods (mean success rate 24.1%, range 16.5% to 32.2%).

Antibodies against Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae and influenza virus and their relationships with risk factors, clinical signs and lung lesions in pig farms with one-site production systems in Brazil.

A study was conducted on 21 pig herds using one-site production system in the southeast region of Brazil to assess the relationships among serological results for primary pathogens involved in respiratory diseases (Actinobacillus pleuropneumoniae, App; Mycoplasma hyopneumoniae, Mhyo; and swine influenza virus, SIV), cough index, pneumonia index, pleuritis and herd characteristics. The prevalence of antibodies against Mhyo and SIV increased throughout the raising phases, with the highest prevalence in slaughtered pigs (> 40%), while pigs in 65% (14/21) of nurseries demonstrated marked seroprevalence of App that decreased until the day of slaughter. Pleuritis and pulmonary consolidations were recorded in 9.0 and 72.4%, respectively, of the 908 evaluated lungs. Histopathological analysis of the lung lesions revealed suppurative bronchopneumonia in almost half of the lungs (48.9%). Regression analyses were conducted to identify risk factors associated with the cough index; pleuritis; pulmonary consolidation; and App, Mhyo and SIV serological results. All-in-all-out management in nursery buildings reduced the seroprevalence of Mhyo in herds. App seroprevalence was associated with pleuritis, and the presence of cough episodes in growing pigs was associated with SIV seropositivity in nursery pigs.

Implementation of PRRSV status classification system in swine breeding herds from a large integrated group in Spain.

BACKGROUND: Porcine Reproductive and Respiratory Syndrome (PRRS) is an endemic swine disease causing significant productive and economic losses. Knowledge of PRRS epidemiology is crucial to develop control strategies against this disease. In that regard, classifying farms according to PRRS virus (PRRSV) shedding and exposure, and understanding key drivers of change in status over time, provides great applied knowledge for developing disease control programs. In most European countries, PRRSV monitoring is performed most frequently at the individual farm level although criteria selected for monitoring varies among different regions and farms. The aim of this study was to implement a systematic monitoring program for PRRSV in Spanish sow farms. Breeding herds were classified according to a standardized PRRSV infection status using sampling programs and terminology currently adopted in the United States (US), which allowed an evaluation of PRRSV epidemiology in a large integrated Spanish group during a one-year study period (February 2017-March 2018). RESULTS: Fifteen farms achieved a stable PRRSV status after the first 4 consecutive samplings and 20 farms were classified as unstable. One of the farms maintained a stable status throughout the duration of the whole monitoring period.Among the 20 farms classified as unstable at the beginning of the monitoring protocol, 9 farms (45%) never reached the stable status and 11 farms (55%) reached stable status afterwards during the monitoring study period.From PRRSV PCR positive pools, there were 47 different PRRSV nucleotide sequences from 24 different farms. More than one PRRSV sequence was obtained from 15 farms. In the farms with more than one sequence detected, we observed recirculation of the same PRRSV field strain in 7 farms and introduction of a different PRRSV strain in 5 farms and both events in 3 farms. CONCLUSIONS: Systematic monitoring for PRRSV in breeding herds established a basis of knowledge of PRRSV epidemiology at the farm level and provided key data to classify farms according to PRRSV exposure and shedding status. These data allow further evaluation of the impact of the PRRSV farm status on production and economic performance in breeding herds and additional investigation of factors related to PRRSV epidemiology.

Assessment of abattoir based monitoring of PRRSV using oral fluids.

Various porcine reproductive and respiratory syndrome virus (PRRSV) regional elimination projects have been implemented in the U.S., but none have yet succeeded. In part, this reflects the need for efficient methods to monitor over time the progress of PRRSV status of participating herds. This study assessed the feasibility of monitoring PRRSV using oral fluids collected at the abattoir. A total of 36 pig lots were included in the study. On-farm oral fluid (n = 10) and serum (n = 10) collected within two days of shipment to the abattoir were used to establish the reference PRRSV status of the population. Oral fluids (n = 3 per lot) were successfully collected from 32 lots (89%) at the lairage. Three veterinary diagnostic laboratories (VDLs) tested the sera (VDL1 and VDL3: n = 316, VDL2: n = 315) and oral fluids (VDL1 and VDL3: n = 319, VDL2: n = 320) for PRRSV antibodies (ELISA) and RNA (rRT-PCR). Environmental samples (n = 64, 32 before and 32 after pigs were placed in lairage) were tested for PRRSV RNA at one VDL. All oral fluids (farm and abattoir) tested positive for PRRSV antibody at all VDLs. PRRSV positivity frequency on serum ranged from 92.4% to 94.6% among VDLs, with an overall agreement of 97.6%. RNA was detected on 1.3% to 1.9%, 8.1% to 17.7%, and 8.3% to 17.7% of sera, on-farm and abattoir oral fluids, respectively. Between-VDLs rRT-PCR agreement on sera and oral fluids (farm and abattoir) ranged from 97.8% to 99.0%, and 79.0% to 81.2%, respectively. Between-locations agreement of oral fluids varied from 31.3% to 50% depending on the VDL. This study reported the application of swine oral fluids collected at the abattoir for monitoring PRRSV, and describes the between-VDL agreement for PRRS testing of serum and oral fluid field samples.

Detection of atypical porcine pestivirus in Brazil in the central nervous system of suckling piglets with congenital tremor.

Atypical porcine pestivirus (APPV) has been detected in piglets with congenital tremor (CT) from three different continents including North America, Europe and Asia. Thirteen piglets from four farms in two different states in Brazil with CT were sampled. Viral RNA was detected by quantitative real-time PCR in the cerebellum or cerebellum and spinal cord in the 100% of the piglets with CT, and APPV was not detected in any tissue sample from clinically non-affected piglets with the exception of the cerebellum of one piglet from Farm A. Piglets with CT had an odds ratio of 99.0 (95% CI 3.4, 2823.8; p = .0072) compared to piglets without CT to test positive for APPV by qRT-PCR. A subset of positive samples was selected for sequencing of the NS3 gene. Phylogenetic analysis revealed that Brazilian sequences of the NS3 formed an independent cluster and had the highest sequence identity with a sequence from the United States. This is the first identification of APPV infection in piglets with CT in South America.

Monitoring breeding herd production data to detect PRRSV outbreaks.

Porcine reproductive and respiratory syndrome virus (PRRSv) causes substantial economic impact due to significant losses in productivity. Thus, measuring changes in farm productivity before and after PRRS infection enables quantifying the production and economic impact of outbreaks. This study assessed the application of exponentially weighted moving average (EWMA), a statistical process control method, on selected production data (number of abortions, pre-weaning mortality rate and prenatal losses) to supplement PRRS surveillance programs by detecting significant deviations on productivity in a production system with 55,000 sows in 14 breed-to-wean herds in Minnesota, U.S.A. Weekly data from diagnostic monitoring program (available through the Morrison's Swine Health Monitoring Project) implemented on the same herds was used as reference for PRRS status. The time-to-detect, percentage of early detection of PRRSv-associated productivity deviations, and relative sensitivity and specificity of the production data monitoring system were determined relative to the MSHMP. The time-to-detect deviations on productivity associated with PRRS outbreaks using the EWMA method was -4 to -1 weeks (interquartile range) for the number of abortions, 0-0 for preweaning mortality and -1 to 3 weeks for prenatal losses compared to the date it was reported in the MSHMP database. Overall, the models had high relative sensitivity (range 85.7-100%) and specificity (range 98.5%-99.6%) when comparing to the changes in PRRS status reported in the MSHMP database. In summary, the use of systematic data monitoring showed a high concordance compared to the MSHMP-reported outbreaks indicating that on-farm staff and veterinary oversight were efficient to detect PRRSv, but can be more efficient if they were monitoring closely the frequency of abortions. The systematic monitoring of production indicators using EWMA offers opportunity to standardize and semi-automate the detection of deviations on productivity associated with PRRS infection, offering opportunity to early detect outbreaks and/or to quantify the production losses attributed to PRRS infection.

Effect of immunologic solutions on sows and gilts on time to stability, and production losses in breeding herds infected with 1-7-4 PRRSv.

Porcine reproductive and respiratory syndrome virus (PRRSv) is an economically significant swine pathogen causing production losses in the global swine industry. Clinical impact depends on many factors including the virus itself. One method to sub-type PRRSv is using restriction fragment length polymorphism (RFLP). The RFLP pattern 1-7-4 emerged within the United States swine industry in 2014 and has become prevalent since then. This was a field study that prospectively followed 1-7-4-infected breeding herds (n=107) and compared time to stability (TTS), time to baseline production (TTBP) and total loss per 1000 sows between herds using modified-live virus vaccine (MLV) on sows and gilts (MLV-MLV), MLV on sows and MLV in addition to field virus exposure on gilts (MLV-MLV/FVE) or not deliberately exposing sows or gilts to PRRSv (Natural-Natural). Analyses were done in SAS 9.4 and results were adjusted by selected co-variates (duration of herd closure, number of previous PRRSv outbreaks of last 3 years, weaning frequency/week, gilt development unit location, herd size and production system). Survival analysis was conducted on TTS and TTBP and regression analysis on total loss. Herds in the Natural-Natural group achieved TTS and TTBP before other herds. Herds in the MLV-MLV/FVE had the longest TTS and TTBP. The total loss was numerically least in MLV-MLV herds (1194 pigs/1000 sows) compared to MLV/MLV-FVE (1810/1000 sows) and Natural-Natural (2671/1000 sows). This study provided additional information to assist veterinarians deciding between methods of exposure to manage PRRSv infection from breeding herds.

Systematic Epidemiological Investigations of Cases of Senecavirus A in US Swine Breeding Herds.

Epidemiological investigations were conducted on a case series of six Senecavirus A (SVA)-affected breeding herds in the United States to determine potential routes of introduction and enhance the swine industry's knowledge of SVA's clinical presentation and spread. Each SVA-affected herd was evaluated using a standard form to ensure that all relevant data were collected. The form was used to guide a detailed discussion about the clinical presentation of SVA and risk events that occurred in the 4 weeks prior to the first observation of clinical signs with the herd veterinarian and farm personnel. Each event was then subjectively assigned a risk level of low, medium or high likelihood for SVA introduction by the investigation team. The clinical presentation of SVA varied by case. All SVA-affected herds (six of six) reported increases in pre-weaning mortality and sow anorexia. Vesicular lesions were observed in four of six herds, and mild-to-moderate neonatal diarrhoea was observed in three of six herds. No gross anatomic or histologic lesions were observed in neonatal pigs that tested positive for SVA via PCR. Multiple potential routes of introduction were identified. Events subjectively rated as high risk for SVA introduction were on-farm employee entry (six of six), carcass disposal (four of six), cull sow removal (three of six) and breeding replacement entry (two of six). Non-swine domestic animals, rodents, other visitors, repairs outside swine barns, feed delivery, weaned pig removal and semen entry were assigned a high risk level in one of six herds. Cases occurred in breeding herds of all sizes with variable biosecurity in both swine dense and swine sparse areas.

Neonatal Mortality, Vesicular Lesions and Lameness Associated with Senecavirus A in a U.S. Sow Farm.

A 300-sow farrow-to-finish swine operation in the United States experienced a sudden and severe increase in mortality in neonatal piglets with high morbidity followed by vesicular lesions on the snout and feet of adult females and males. Affected live piglets were submitted for diagnostic investigation. Samples tested polymerase chain reaction (PCR) negative for foot-and-mouth disease virus, porcine delta coronavirus, porcine epidemic diarrhoea virus, porcine rotavirus types A, B and C, transmissible gastroenteritis virus, and porcine reproductive and respiratory syndrome virus. Senecavirus A (SV-A) formerly known as Seneca Valley virus was detected by real-time reverse-transcription polymerase chain reaction (rRT-PCR) from serum, skin and faeces of piglets and from serum and faeces of sows. SV-A was isolated in cell culture from piglet samples. SV-A VP1 gene region sequencing from piglet tissues was also successful. A biosecurity and disease entry evaluation was conducted and identified potential biosecurity risks factors for the entry of new pathogens into the operation. This is the first case report in the United States associating SV-A with a clinical course of severe but transient neonatal morbidity and mortality followed by vesicular lesions in breeding stock animals. Veterinarians and animal caretakers must remain vigilant for vesicular foreign animal diseases and report suspicious clinical signs and lesions to state animal health authorities for diagnostic testing and further investigation.

Identification and Complete Genome of Seneca Valley Virus in Vesicular Fluid and Sera of Pigs Affected with Idiopathic Vesicular Disease, Brazil.

Numerous, ongoing outbreaks in Brazilian swine herds have been characterized by vesicular lesions in sows and acute losses of neonatal piglets. The complete genome of Seneca Valley virus (SVV) was identified in vesicular fluid and sera of sows, providing evidence of association between SVV and vesicular disease and viraemia in affected animals.

Comparison of time to PRRSv-stability and production losses between two exposure programs to control PRRSv in sow herds.

To control and eliminate porcine reproductive and respiratory syndrome virus (PRRSv) from breeding herds, some veterinarians adopt a strategy called load-close-expose which consists of interrupting replacement pig introduction for several months and exposing the pigs to a replicating PRRSv. This was a prospective quasi-experiment that followed 61 breeding herds acutely infected with PRRSv that adopted one of two exposure programs: modified-live virus (MLV) vaccine or live-resident virus inoculation (LVI). Treatment groups (load-close-expose with MLV or LVI) were compared for: (a) time-to-PRRSv stability (TTS), defined as time in weeks it took to produce PRRSv negative pigs at weaning; (b) the time-to-baseline production (TTBP), defined using statistical process control methods to represent time to recover to the number of pigs weaned per week that herds had prior to PRRSv-detection; and (c) the total production loss in terms of number of pigs weaned per week. TTS and TTBP were compared between treatments using survival analysis. Day 1 of the program was considered to be the day that treatment was administered. Sampling at herds consisted of bleeding 30 due-to-wean piglets on a monthly basis. Serum was tested for PRRSv RNA by RT-PCR. Herds in which PRRSv was not detected over a 90-day period were classified as reaching stability. Multivariate analysis using proportional hazards regression was performed adjusting the effect of treatment on TTBP and TTS to 'severity of PRRSv infection', 'number of whole-herd exposures', 'days from PRRSv-detection to intervention', 'prior PRRSv-infection status' and 'veterinary clinic associated with the herd'. Total loss was compared between groups using multivariate regression analysis adjusted by selected covariates. The median TTS among participating herds was 26.6 weeks (25th to 75th percentile, 21.6-33.0 weeks). The overall TTBP was 16.5 weeks (range 0-29 weeks). The magnitude of production losses following whole-herd exposure averaged 2217 pigs not weaned/1000 sows and was correlated with TTBP. Herds in the MLV group recovered production sooner and had less total loss than herds in the LVI group. TTBP and TTS were significantly shorter and the total loss was significantly less in herds assisted by a specific veterinary clinic and herds that were infected with PRRSv in the 3 years prior to the study. This study provided new metrics to assist veterinarians to decide between methods of exposure to control and eliminate PRRSv from breeding herds.