Determination of the frequency of individuals with broadly cross-reactive neutralizing antibodies against PRRSV in the sow population under field conditions.

BACKGROUND: Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) is a significant swine pathogen, yet the immune response components contributing to protection remain incompletely understood. Broadly reactive neutralizing antibodies (bNAs) may play a crucial role in preventing reinfections by heterologous viruses, although their occurrence is considered low under both field and experimental conditions. This study aimed to assess the frequency of sows exhibiting bNAs against PRRSV under field conditions and to analyze the epidemiological factors influencing the occurrence of these elite neutralizers. Blood samples were collected from breeding sows across eleven unrelated pig farms, with samples categorized by parity. Serum obtained was utilized in virus neutralization assays (VNs) against six PRRSV field isolates and two MLV strains. RESULTS: Approximately 7% of the sows exhibited neutralization activity against all viruses in the panel, with a geometric mean of the titer (GMT) of NAs at or exceeding 4 log2. Exclusion of the PRRSV-2 isolate from the panel increased the proportion of elite neutralizers to around 15%. Farm-specific analysis revealed significant variations in both GMT of NAs and proportion of elite neutralizers. PRRSV unstable farms and those with a PRRS outbreak in the last 12 months displayed higher GMT of NAs compared to stable farms without recent outbreaks. The GMT of NAs showed a gradual, albeit moderate, increase with the parity of the sows. Parity's impact on bNA response was consistently observed in stable farms but not necessarily in unstable farms or those with recent outbreaks. Finally, the results indicated that vaccinated animals had higher NA titers against the vaccine virus used in the farm than against field viruses. CONCLUSION: bNAs against heterologous isolates induced by PRRSV infection under field conditions are generally low, often falling below titers necessary for protection against reproductive failure. However, a subset of sows (approximately 15%) can be considered elite neutralizers, efficiently recognizing various PRRSV strains. Repeated exposures to PRRSV play a crucial role in eliciting these bNAs, with a higher frequency observed in unstable farms and those with recent outbreaks. In stable farms, parity only marginally influences bNA titers, highlighting its limited role compared to the impact of PRRSV exposure history.

Perception about the Major Health Challenges in Different Swine Production Stages in Spain.

One of the main challenges for the sustainability and productivity of the Spanish swine industry is health instability, resulting in significant economic losses. Information on the main swine diseases which affect the Spanish pig industry could help in optimizing the efforts within control programs. This study determined the frequency of occurrence of the main diseases in Spain and the main control tool used, based on perceptions from veterinarians and consultants in a specific survey. Results showed that Streptococcus (S.) suis, E. coli, and coccidia are the most frequent pathogens in the gestation and lactation phase, whereas the most important were Porcine Reproductive and Respiratory Syndrome virus (PRRSV). In the nursery phase, the most frequent were S. suis, E. coli, and PRRSV, the latter being the most important for the participants. Finally, in the fattening phase, PRRSV and Actinobacillus pleuropneumoniae were the most frequent and important pathogen, respectively. Statistical differences among responses were detected with respect to the location and the gestation and lactation phases by farm size. Regarding the tools used for controlling the diseases, vaccination was the main strategy in all production phases, except in the fattening period, in which antibiotherapy was the most common response from the participants. Finally, the improvement of management practices was the most proposed tool, suggesting its importance within control programs.

Frequency of PCV-2 viremia in nursery piglets from a Spanish swine integration system in 2020 and 2022 considering PRRSV infection status.

BACKGROUND: Porcine circovirus 2 (PCV-2) poses a significant economic threat for the swine industry, causing a range of diseases collectively referred to as porcine circovirus diseases (PCVDs). Despite PCV-2 vaccine effectiveness, the need for monitoring infectious pressure remains. PCV-2 coinfection with other pathogens like porcine reproductive and respiratory syndrome virus (PRRSV) can exacerbate disease severity and lead to PCV-2-systemic disease cases. Monitoring both PRRSV and PCV-2 in co-infected farms is crucial for an effective management and vaccination programs. The present cross-sectional study aimed to determine PCV-2 antibody levels in piglets at weaning and PCV-2 and PRRSV viremia in pooled serum samples at weaning (vaccination age) and at 6 and 9 weeks of age from a Spanish swine integration system in 2020 (48 farms) and in 2022 (28 out of the 48 analysed previously). RESULTS: The frequency of PCV-2 detection in pools of piglet sera was 2.1% (2020) and 7.1% (2022) at vaccination age but increased at the end of the nursery period (10.4% in 2020 and 39.3% in 2022) in both years. Co-infections between PCV-2 and PRRSV were detected in a significant proportion of PRRSV positive farms (15% in 2020, and 60% in 2022). PCV-2 antibody levels (ELISA S/P ratios) at weaning were lower in PCV-2 qPCR positive farms at different sampling time-points (0.361 in 2020 and 0.378 in 2022) compared to PCV-2 qPCR negative ones (0.587 in 2020 and 0.541 in 2022). The 28 farms tested both years were classified in four different epidemiological scenarios depending on their PCV-2 virological status. Those PCV-2 qPCR negative farms in 2020 that turned to be positive in 2022 had a statistically significant increase of PRRSV RT-qPCR detection and a PCV-2 antibody levels reduction, facts that were not observed in the rest of the scenarios. CONCLUSION: This epidemiological study in farms from the same integration system determined the occurrence, in 2020 and in 2022, of PCV-2 and PRRSV infections in piglets during the nursery period by using pooled serum samples.

Environmental detection of Mycoplasma hyopneumoniae in breed-to-wean farms.

There is a need to develop cost-effective and non-invasive approaches to sample large populations to evaluate the disease status of breeding herds. In this study we assessed the detection of the M. hyopneumoniae genetic material in environmental surfaces and air of farrowing rooms, and skin (udder, snout and vagina) of lactating sows at weaning, in farms having different M. hyopneumoniae infection status (negative, positive sub-clinically infected and positive clinically affected). Mycoplasma hyopneumoniae was detected in air, air deposition particles, dam and stall surfaces of the positive clinically affected herd. Mycoplasma hyopneumoniae could only be detected in dam and stall surfaces in sub-clinically infected herds. Mycoplasma hyopneumoniae was not detected in all samples collected in the negative herd. The cycle threshold of the positive PCR samples were not statistically different between sample types or farms. However, a significant difference (p < 0.05) was observed in the percentage of positive samples between the positive clinically affected farm and the rest. Likewise, M. hyopneumoniae was detected in the environment and surfaces at weaning in positive breeding herds. Further testing and validation is recommended for environmental and surface samples before they can be employed as part of the M. hyopneumoniae diagnostic process. In addition, results from this study highlight potential sources of M. hyopneumoniae infection for piglets in breeding herds, especially during an outbreak.

Impact of maternally derived immunity on immune responses elicited by piglet early vaccination against the most common pathogens involved in porcine respiratory disease complex.

BACKGROUND: Newborn piglets can trigger an elementary immune response, but the acquirement of specific antibodies and/or cellular immunity against pathogens before they get infected post-natally is paramount to preserve their health. This is especially important for the pathogens involved in porcine respiratory disease complex (PRDC) as they are widespread, fairly resistant at environment, and genetically variable; moreover, some of them can cause intrauterine/early life infections. MAIN BODY: Piglet protection can be achieved by either passive transfer of maternal derived immunity (MDI) and/or actively through vaccination. However, vaccinating piglets in the presence of remaining MDI might interfere with vaccine efficacy. Hence, the purpose of this work is to critically review the putative interference that MDI may exert on vaccine efficacy against PRDC pathogens. This knowledge is crucial to design a proper vaccination schedule. CONCLUSION: MDI transferred from sows to offspring could potentially interfere with the development of an active humoral immune response. However, no conclusive interference has been shown regarding performance parameters based on the existing published literature.

Mycoplasma hyopneumoniae variability: Current trends and proposed terminology for genomic classification.

Mycoplasma hyopneumoniae (M. hyopneumoniae) is the aetiologic agent of enzootic pneumonia in swine, a prevalent chronic respiratory disease worldwide. Mycoplasma hyopneumoniae is a small, self-replicating microorganism that possesses several characteristics allowing for limited biosynthetic abilities, resulting in the fastidious, host-specific growth and unique pathogenic properties of this microorganism. Variation across several isolates of M. hyopneumoniae has been described at antigenic, proteomic, transcriptomic, pathogenic and genomic levels. The microorganism possesses a minimal number of genes that regulate the transcription process. Post-translational modifications (PTM) occur frequently in a wide range of functional proteins. The PTM by which M. hyopneumoniae regulates its surface topography could play key roles in cell adhesion, evasion and/or modulation of the host immune system. The clinical outcome of M. hyopneumoniae infections is determined by different factors, such as housing conditions, management practices, co-infections and also by virulence differences among M. hyopneumoniae isolates. Factors contributing to adherence and colonization as well as the capacity to modulate inflammatory and immune responses might be crucial. Different components of the cell membrane (i.e. proteins, glycoproteins and lipoproteins) may serve as adhesins and/or be toxic for the respiratory tract cells. Mechanisms leading to virulence are complex and more research is needed to identify markers for virulence. The utilization of typing methods and complete or partial-gene sequencing for M. hyopneumoniae characterization has increased in diagnostic laboratories as control and elimination strategies for this microorganism are attempted worldwide. A commonly employed molecular typing method for M. hyopneumoniae is Multiple-Locus Variable number tandem repeat Analysis (MLVA). The agreement of a shared terminology and classification for the various techniques, specifically MLVA, has not been described, which makes inferences across the literature unsuitable. Therefore, molecular trends for M. hyopneumoniae have been outlined and a common terminology and classification based on Variable Number Tandem Repeats (VNTR) types has been proposed.

Characterization of Mycoplasma hyopneumoniae strains in vaccinated and non-vaccinated pigs from Spanish slaughterhouses.

This study aimed to describe Mycoplasma hyopneumoniae (M. hyopneumoniae) genetic variability in vaccinated (V) and non-vaccinated (NV) slaughtered pigs showing cranio-ventral pulmonary consolidation (CVPC). Ten V and 10 NV fattening farms with respiratory problems associated to M. hyopneumoniae were selected. Lung lesions of one batch per farm were scored at slaughterhouse and the enzootic pneumonia (EP)-index was calculated. Moreover, three lungs showing the most extensive CVPC per farm were sampled and tested for M. hyopneumoniae detection by real-time (rt)-PCR. Positive samples with cycle threshold ≤30 were selected to be genotyped by sequencing of four loci (P97, P146, H1 and H5). Typing profiles (TP) were assigned considering four or two (P97, P146) loci. Five commercial vaccines for M. hyopneumoniae (VS) and two reference strains (RF) were also genotyped. The EP-index (mean ± SD) in NV farms (3.8 ± 1.9) was not significantly different from V ones (2.2 ± 1.3). From the 60 selected lungs, 46 (76.7%) were M. hyopneumoniae positive by rt-PCR (25/30 and 21/30 from NV and V farms, respectively), and 43 (93.5%) of those were successfully genotyped. A total of 24 different TP(12 in V and 12 in NV farms) or 17 TP(9 in V and 9 in NV farms, being one TP in both farm types) were identified by analyzing four or two loci, respectively. One to three TP per farm were detected, being different from VS and RF. Interestingly, farms with same breeding origin had the same TP using two loci, but such link was not found using four loci. Therefore, high inter-farm and limited intra-farm M. hyopneumoniae genetic variability were detected, but variability depended on the number of studied loci.

Comparison of vaccination protocols against Mycoplasma hyopneumoniae during the gilt acclimation period.

This study evaluated different gilt vaccination protocols against Mycoplasma (M.) hyopneumoniae at acclimation and their effect on the genetic diversity. A total of 180 M. hyopneumoniae naïve gilts were selected 1 week post-entry (wpe) at the acclimation barn in a clinically affected M. hyopneumoniae farm. Gilts were distributed according to the M. hyopneumoniae antibodies levels into three different vaccination schedules: A) four doses of a M. hyopneumoniae commercial vaccine at 2, 4, 6 and 8 wpe; B) two vaccine doses at 2 and 6 wpe and PBS at 4 and 8 wpe; and C) four PBS doses at the same wpe. Detection of M. hyopneumoniae (rt-PCR) and antibodies (ELISA) were assessed in gilts at 1, 14, 27 and 34 wpe and in 6 of their piglets at weaning. Rt-PCR positive gilts were detected at 14 wpe, being the proportion significantly lower in groups A and B (3/120, 3%) than C (27/60, 45%). Seroconversion was detected at 14 wpe, showing significant differences in percentage of inhibition (PI) between groups A (median 4.9, range 3.1-19.9) and B (5.5, 3.7-13.5), and C (14.3, 3.3-53.2). Gilts remained seropositive over the study and significant differences in PI were detected between groups A and B versus C. All piglets were rt-PCR negative, but the proportion of seropositive piglets coming from vaccinated gilts was significantly higher than the non-vaccinated group. M. hyopneumoniae characterization showed high variability. Hence, gilt vaccination with 2 or 4 doses significantly decreased the pathogen infectious pressure, variability, and provided high antibody levels to gilts and their offspring.

Acclimation strategies in gilts to control Mycoplasma hyopneumoniae infection.

Mycoplasma hyopneumoniae (M. hyopneumoniae) is the primary causative agent of enzootic pneumonia (EP), one of the most economically important infectious disease for the swine industry worldwide. M. hyopneumoniae transmission occurs mainly by direct contact (nose-to-nose) between infected to susceptible pigs as well as from infected dams to their offspring (sow-to-piglet). Since disease severity has been correlated with M. hyopneumoniae prevalence at weaning in some studies, and gilts are considered the main bacterial shedders, an effective gilt acclimation program should help controlling M. hyopneumoniae in swine farms. The present review summarizes the different M. hyopneumoniae monitoring strategies of incoming gilts and recipient herd and proposes a farm classification according to their health statuses. The medication and vaccination programs against M. hyopneumoniae most used in replacement gilts are reviewed as well. Gilt replacement acclimation against M. hyopneumoniae in Europe and North America indicates that vaccination is the main strategy used, but there is a current trend in US to deliberately expose gilts to the pathogen.

Survey on Mycoplasma hyopneumoniae gilt acclimation practices in Europe.

Gilts are considered to play a key role in Mycoplasma hyopneumoniae (M. hyopneumoniae) transmission and control. An effective gilt acclimation program should ideally reduce M. hyopneumoniae shedding at first farrowing, decreasing pre-weaning colonization prevalence and potential respiratory problems in fatteners. However, information on gilt acclimation practices is scarce in Europe. The aim of this study was to identify current acclimation strategies for M. hyopneumoniae in Europe using a questionnaire designed to assess 15 questions focused on gilt replacement status, acclimation strategies and methods used to ascertain its effect. A total of 321 questionnaires (representing 321 farms) were voluntarily completed by 108 veterinarians (from 18 European countries). From these farms, 280 out of 321 (87.2%) were aware of the health status of gilts on arrival. From these 280 farms, 161 (57.5%) introduced M. hyopneumoniae positive replacements. In addition, 249 out of 321 (77.6%) farms applied an acclimation process using different strategies, being M. hyopneumoniae vaccination (145 out of 249, 58.2%) and the combination of vaccine and exposure to sows selected for slaughter (53 out of 249, 21.3%) the most commonly used. Notwithstanding, only 53 out of 224 (23.6%) farms, knowing the M. hyopneumoniae initial status and performing acclimation strategies against it, verified the effect of the acclimation by ELISA (22 out of 53, 41.5%), PCR (4 out of 53, 7.5%) or both (27 out of 53, 50.9%). This study showed that three fourths of the farms represented in this European survey have M. hyopneumoniae acclimation strategies for gilts, and one fifth of them verify to some extent the effect of the process. Taking into account that the assessment of acclimation efficacy could help in optimizing replacement gilt introduction into the breeding herd, it seems these practices for M. hyopneumoniae are still poorly developed in Europe.