Infectious agents associated with respiratory diseases in 125 farrow-to-finish pig herds: a cross-sectional study

Mycoplasma hyopneumoniae - an unusual cause of fibrinous pericarditis with pericardial tamponade in pre-weaned piglets

M. hyopneumoniae is an atypical bacterium that is frequently associated with porcine enzootic pneumonia, but uncommonly identified as a cause of pericarditis and myocarditis leading to pericardial tamponade. The present report describes the rare case of M. hyopneumoniae causing fibrinous pericarditis and pericardial tamponade in pre-weaned crossbred piglets (n = 7). The piglets showed the predominant lesions of pericardial effusions with tamponade, fibrinous pericarditis, pleural effusions, heavy non-collapsible lungs with multifocal reddish areas on parenchyma, and enlarged lymph nodes. Microscopically, sub-acute fibrinous pericarditis, pleuritis, brocho-interstitial pneumonia with lymphoid depletion in the lymphoid organs were the consistent lesions observed in the piglets. The piglets showed the strong immunoreactivity to M. hyopneumoniae antigens in the infiltrating mononuclear cells, cardiomyocytes, and purkinje fibers of heart, bronchioles, and alveolar lining epithelium of lungs, and lymphocytes of the depleted lymphoid follicles of the lymph nodes. The absence of immunoreactivity to M. hyorhinis in the heart ruled out the cross specificity and confirmed the involvement of M. hyopneumoniae with the cardiac pathologies. Further, M. hyopneumoniae was confirmed in heart, pericardium, and lungs of the piglets by PCR suggesting the role of M. hyopneumoniae with the cardiac lesions. The absence of any other possible etiologies (bacteria/and virus) in the heart tissues further confirms M. hyopneumoniae as a cause of cardiac lesions. Among various viruses screened, lungs, lymph nodes, and liver of the piglets showed the genomic detection of porcine circovirus 2 along with strong cytoplasmic immunolabeling of viral antigens in lungs and lymph nodes. This indicates that co-infection of M. hyopneumoniae and porcine circovirus 2 might be playing a synergistic role by potentiating each other in causing severe pathologies involving lungs and heart. This paper highlights that M. hyopneumoniae should be considered in the differential diagnosis of pneumonia complicated by pericardial effusion leading to complication of pericardial tamponade and should be part of the routine workup for pericarditis of unknown etiology for the effective control and management of piglet mortality. Moreover, the presence of immunosuppressive disease like porcine circovirus 2 has also to be considered as the predisposing factor for the development of fibrinous pericarditis.

Efficacy and safety of intradermal vaccination against porcine circovirus type 2 and Mycoplasma hyopneumoniae under combined exposure field conditions

BACKGROUND

Porcine circovirus 2 (PCV2) and Mycoplasma hyopneumoniae (M hyo) are two of the most important swine pathogens with variable clinical presence in swine farms globally, affecting health and performance of pigs under field conditions. The primary objective of this study was to assess the efficacy of a ready to use intradermal (ID) vaccine (Porcilis PCV M Hyo ID, MSD Animal Health, The Netherlands) against PCV2 associated disease and M hyo associated enzootic pneumonia under practical (field) conditions. In addition, the safety of the test product was clinically assessed, as the study animals were examined for general and local side effects after vaccination. A total of 678 animals in a Greek farrow to finish farm were equally divided in two trial groups (test and control group). Test group animals received the test vaccine at the age of three weeks, while control group animals remained unvaccinated. Parameters regarding health [lung lesion score (LLS) and pleurisy scoring, PCV2 viraemia and shedding] and performance [body weight (BW), average daily weight gain (ADWG)] were recorded and evaluated.

RESULTS

Vaccination improved the ADWG during both the finishing period (improvement by 34 g; p < 0.0001), and the overall period (increase by 24 g; p < 0.0001). Moreover, reduced mean LLS values (p < 0.0001), as well as reduced percentage of animals with pleurisy (p = 0.0082) and a decrease in PCV2 viraemia (p < 0.0001) and viral shedding (p = 0.0181) were observed in vaccinated animals when compared with the unvaccinated controls. As regards safety, a slight local skin reaction at the site of vaccination was detected and in two pigs a mild systemic reaction was reported with full recovery.

CONCLUSIONS

Findings suggested that the test vaccine is safe and effective against both PCV2 and M hyo associated diseases in vivo, thus it's use as part of a vaccination programme under field conditions is expected to improve respective health and performance parameters in pigs.

Serovar and multilocus sequence typing analysis of Pasteurella multocida from diseased pigs in Taiwan

BACKGROUND

Pasteurella multocida causes progressive atrophic rhinitis and suppurative bronchopneumonia in pigs, which results in severe economic losses in swine industry. This study aimed to determine the serovar, genotype and prevalence of toxA virulence gene of Pasteurella multocida isolates collected in Taiwan. A total of 164 Pasteurella multocida isolates from 161 diseased pigs were characterized by serotyping, multilocus sequence typing (MLST), antimicrobial susceptibility testing, and the presence of virulence gene (toxA) and antibiotic resistance gene (floR).

RESULTS

The majority of Pasteurella multocida strains were serovar D:L6 (48.2%; 79/164) followed by A:L6 (28.7%; 47/164) and A:L3 (19.5%; 32/164). More than 80% of strains carrying toxA gene belonged to serovar A:L6 (82.6%; 19/23). The MLST data showed five sequence types (STs), where multi-host ST10 was the most dominant. Most Pasteurella multocida strains of multi-host ST10 were serovar A:L6 (93.9%; 31/33), which suggested that STs were highly associated with specific serovars. Most of the floR-carrying Pasteurella multocida strains belonged to serovar D:L6 with significantly high resistance to some antimicrobial agents, especially florfenicol.

CONCLUSIONS

This study demonstrated that serovar D:L6 and multi-host ST10 was the most prevalent Pasteurella multocida strain in Taiwan. A:L6 accounted for the majority of toxA-positive strains and the presence of floR gene may be responsible for the antimicrobial resistance to florfenicol.

Improvement in the Usability of Meat Inspection Findings for Swine Herd Health Management

Data from post-mortem inspections conducted using official controls on the meat production of slaughtered pigs are generally considered valuable for identifying herd health issues and ensuring meat safety. However, several studies highlighted that a multi-stage assessment of lung changes would provide more useful information on animal health than the implemented binary (yes/no) recording. For this purpose, a new scheme was developed and subsequently used by trained official veterinarians at four slaughterhouses in Austria. Implementation of the multi-stage assessment was carried out in parallel with the conventional assessment, and data collected from both schemes were analyzed and compared to evaluate effectiveness. The analysis of the data (n = 20,345) showed that the most common alteration was low-grade (28.4%), followed by moderate-grade (11.3%,) and then high-grade pneumonia (5.2%). In the case of pleurisy, 88.9% of the carcasses showed no alterations of the pleura, and 11.1% had pathological changes (low-grade pleurisy = 4.7%, moderate-grade pleurisy = 2.7%, high-grade pleurisy = 3.7%). Analysis of the results showed a strong heterogeneity of the frequency of alterations between the batches reflecting various underlying animal health issues. Among the influencing factors, the origin of the pigs had the greatest influence. The project demonstrated that the new evaluation can be carried out easily with no extra time effort once staff are trained and the technological platform for reporting is adapted. The more detailed information ensures more useful feedback is provided to the farmers and supervising veterinarians, thereby ensuing animal welfare and contributing to sustainable, improved animal husbandry.

Scoring of swine lung images: a comparison between a computer vision system and human evaluators

Cranioventral pulmonary consolidation (CVPC) is a common lesion observed in the lungs of slaughtered pigs, often associated with Mycoplasma (M.) hyopneumoniae infection. There is a need to implement simple, fast, and valid CVPC scoring methods. Therefore, this study aimed to compare CVPC scores provided by a computer vision system (CVS; AI DIAGNOS) from lung images obtained at slaughter, with scores assigned by human evaluators. In addition, intra- and inter-evaluator variability were assessed and compared to intra-CVS variability. A total of 1050 dorsal view images of swine lungs were analyzed. Total lung lesion score, lesion score per lung lobe, and percentage of affected lung area were employed as outcomes for the evaluation. The CVS showed moderate accuracy (62-71%) in discriminating between non-lesioned and lesioned lung lobes in all but the diaphragmatic lobes. A low multiclass classification accuracy at the lung lobe level (24-36%) was observed. A moderate to high inter-evaluator variability was noticed depending on the lung lobe, as shown by the intraclass correlation coefficient (ICC: 0.29-0.6). The intra-evaluator variability was low and similar among the different outcomes and lung lobes, although the observed ICC slightly differed among evaluators. In contrast, the CVS scoring was identical per lobe per image. The results of this study suggest that the CVS AI DIAGNOS could be used as an alternative to the manual scoring of CVPC during slaughter inspections due to its accuracy in binary classification and its perfect consistency in the scoring.

Impact of porcine respiratory disease complex on carcass weight and meatiness: quantitative insights from a mixed-model analysis

BACKGROUND

Porcine respiratory disease complex (PRDC) significantly impacts the swine industry worldwide, leading to economic losses due to poor growth performance, reduced feed efficiency, higher medication costs, and adversely affecting pig welfare by causing clinical symptoms such as fever, cough, loss of appetite, lethargy, and dyspnea. Cranio-ventral pulmonary consolidation (CVPC) and pleuritis are the most frequent macroscopic lung lesions observed in PRDC and are indicators of decreased animal welfare. This study aimed to quantify the effects of CVPC and pleurisy on carcass weight, meatiness, and average daily carcass weight gain (ADCWG) in fattening pigs, thereby assessing their impact on both production and welfare. A total of 679 slaughtered pigs from seven batches (farms) were evaluated for lung lesions at slaughter. We employed a mixed-model analysis to assess the correlation between lung lesions and production parameters across the farms.

RESULTS

The mean prevalence of lesions was 23.86% for CVPC and 15.46% for pleurisy, indicating a significant presence of respiratory disease affecting animal welfare. Pigs with severe lung lesions (≥ 15.1%) exhibited significantly lower ADCWG compared to pigs without lesions (0.951 kg/day vs. 0.997 kg/day, p = 0.024), reflecting reduced growth performance and welfare. The mixed-effects model revealed that lesions in the right apical lobe and dorso-caudal pleurisy were associated with significant reductions in carcass weight (- 2.77 kg and - 2.29 kg, respectively) and carcass meat (- 1.76 kg and - 1.43 kg, respectively). An economic analysis under average market price conditions demonstrated that severe lung lesions could lead to financial losses of up to 11.53 EUR per 100 kg of meat, emphasizing the economic impact of compromised welfare due to respiratory diseases.

CONCLUSIONS

This study provides quantitative evidence of the negative impact of CVPC and pleurisy on carcass weight and meatiness in fattening pigs. The findings underscore the importance of effective respiratory disease management in swine production, highlighting potential areas for targeted interventions to improve animal health and economic outcomes.

The developing pig respiratory microbiome harbors strains antagonistic to common respiratory pathogens

In the global efforts to combat antimicrobial resistance and reduce antimicrobial use in pig production, there is a continuous search for methods to prevent and/or treat infections. Within this scope, we explored the relationship between the developing piglet nasal microbiome and (zoonotic) bacterial pathogens from birth until 10 weeks of life. The nasal microbiome of 54 pigs was longitudinally studied over 16 timepoints on 9 farms in 3 European countries (Germany, Ireland, and the Netherlands) using amplicon sequencing targeting the V3-V4 16S rRNA region as well as the tuf gene for its staphylococcal discrimination power. The piglets' age, the farm, and the litter affected the nasal microbiome, with piglets' age explaining 19% of the variation in microbial composition between samples. Stabilization of the microbiome occurred around 2 weeks post-weaning. Notably, while opportunistic pathogens were ubiquitously present, they did not cause disease. The piglet nasal microbiome often carried species associated with gut, skin, or vagina, which suggests that contact with the vaginal and fecal microbiomes shapes the piglet nasal microbiome. We identified bacterial co-abundance groups of species that were present in the nasal microbiomes in all three countries over time. Anti-correlation between these species and known bacterial pathogens identified species that might be exploited for pathogen reduction. Further experimental evidence is required to confirm these findings. Overall, this study advances our understanding of the piglet nasal microbiome, the factors influencing it, and its longitudinal development, providing insights into its role in health and disease.

IMPORTANCE

Our study on the nasal microbiota development in piglets across farms in three European countries found that the microbiomes developed similarly in all locations. Additionally, we observed that the colonization of porcine pathogens was either positively or negatively associated with the presence of other bacterial species. These findings enhance our knowledge of co-colonizing species in the nasal cavity and the identified microbial interactions that can be explored for the development of interventions to control pathogens in porcine husbandry.

Reverse zoonotic transmission of human seasonal influenza to a pig herd in Sweden

In January 2023, a Swedish piglet-producing farm with 2800 sows in production (SIP) was diagnosed with IAV (Influenza A virus) and the isolates were shown to cluster with the human seasonal influenza (2022/2023). In December 2022, employees with flu like symptoms tended to the pigs and a few weeks later, respiratory signs appeared in different age groups; sows in farrowing units were anorectic and pyrectic. Lung and nasal swabs were tested positive for IAV and other respiratory infectious agents. Blanket vaccination against H1N1pdm09 of sows and gilts was initiated but discontinued for sows after 2 treatments. Biosecurity measures aiming to reduce the spread of virus were implemented. However, the compliance to follow the protocol was moderate.Combining immunity and strict sanitary measures is crucial to control virus circulation. As the farmer discontinued sow vaccination and just partly increased biosecurity, this may have contributed to ongoing virus circulation and clinical signs in pigs, even 5 months post-diagnosis. Although H1N1pdm09 already had been found in the herd in 2017, there were no clinical signs or diagnostic results indicating continuous circulation of this or other IAV strains afterwards. However, this cannot be entirely excluded. Swine IAVs pose a risk of reintroduction into the human population, highlighting the importance of vaccination of farm workers against seasonal influenza.

Impact of swine influenza A virus on porcine reproductive and respiratory syndrome virus infection in alveolar macrophages

Porcine respiratory disease complex represents a major challenge for the swine industry, with swine influenza A virus (swIAV) and porcine reproductive and respiratory syndrome virus (PRRSV) being major contributors. Epidemiological studies have confirmed the co-circulation of these viruses in pig herds, making swIAV-PRRSV co-infections expected. A couple of in vivo co-infection studies have reported replication interferences between these two viruses. Herein, using a reductionist in vitro model, we investigated the potential mechanisms of these in vivo interferences. We first examined the impact of swIAV on porcine alveolar macrophages (AMs) and its effects on AMs co-infection by PRRSV. This was done either in monoculture or in co-culture with respiratory tracheal epithelial cells to represent the complexity of the interactions between the viruses and their respective target cells (epithelial cells for swIAV and AMs for PRRSV). AMs were obtained either from conventional or specific pathogen-free (SPF) pigs. SwIAV replication was abortive in AMs, inducing cell death at high multiplicity of infections. In AMs from three out of four conventional animals, swIAV showed no impact on PRRSV replication. However, inhibition of PRRSV multiplication was observed in AMs from one animal, accompanied by an early increase in the expression of interferon (IFN)-I and IFN-stimulated genes. In AMs from six SPF pigs, swIAV inhibited PRRSV replication in all animals, with an early induction of antiviral genes. Co-culture experiments involving tracheal epithelial cells and AMs from either SPF or conventional pigs all showed swIAV-induced inhibition of PRRSV replication, together with early induction of antiviral genes. These findings highlight the complex interactions between swIAV and PRRSV in porcine AMs, and would suggest a role of host factors, such as sanitary status, in modulating viral propagation. Our co-culture experiments demonstrated that swIAV inhibits PRRSV replication more effectively in the presence of respiratory tracheal epithelial cells, suggesting a synergistic antiviral response between AMs and epithelial cells, consistent with in vivo experiments.

The use of oral fluids and sock samples for monitoring key pathogens in pig populations for surveillance purposes

Despite the prevalence of co-infections and the association of over 50 viral and 46 bacterial pathogens with pig diseases, little is known about their simultaneous occurrence, particularly in commercial pig farming environments where health programs are in place. To address this knowledge gap, this study aimed to evaluate the pathogen threshold of respiratory and enteric pathogens in pig herds using the Pork MultiPath™ (PMP1 and PMP2, respiratory and enteric respectively) technology, which detects multiple pathogens simultaneously in a single reaction with high sensitivity and specificity. In this study the most prevalent respiratory pathogens, Mycoplasma hyrohinis, Pasteurella multocida, and Haemophilus parasuis detected by PMP1 were effectively controlled during the nursery stage through strategic treatment with tiamulin. Even though the major respiratory incidences were reduced, the recorded coughing and sneezing rates were associated with the levels of H. parasuis and M. hyrohinis, which were set at 1356 and 1275 copies/reaction, respectively. In addition, one of the identified co-infection patterns indicated a strong relationship between the occurrence of H. parasuis and M. hyorhinis at the sample and pen levels, highlighting the high likelihood of detecting these two pathogens together. Testing with enteric panel PMP2 revealed that the most frequently detected virulence factors during the early nursery stage were Escherichia coli genes for toxins - ST1, ST2, and fimbriae - F4 and F18. Moreover, a co-infection with Rotavirus B and C was often observed during the nursery stage, and a strong positive correlation between these two markers has been identified. Additionally, the levels of several markers, namely E. coli F4, F5, F18, LT, ST1, and ST2, have been associated with a higher likelihood of sickness in pig populations. In addition, the onset of Brachyspira pilosicoli during the nursery and grower stages was found to be associated with an increased risk of diarrhoea, with a set threshold at around 500 copies/reaction. Although simultaneous detection of multiple pathogens is not yet widely used in the pig industry, it offers a significant advantage in capturing the diversity and interactions of co-infections. Testing pooled samples with Pork MultiPath™ is cost-effective and practical to regularly monitor the health status of pig populations.

Pathological analysis and etiological assessment of pulmonary lesions and its association with pleurisy in slaughtered pigs

The intensification of pig farming has posed significant challenges in managing and preventing sanitary problems, particularly diseases of the respiratory complex. Monitoring at slaughter is an important control tool and cannot be overstated. Hence, this study aimed at characterizing both macroscopical and microscopical lesions and identifying the Actinobacillus pleuropneumoniae (APP), Mycoplasma hyopneumoniae (Mhyo), and Pasteurella multocida (PM) associated with pleurisy in swine. For this, a selected slaughterhouse in São Paulo State underwent a thorough examination of carcasses on the slaughter line, followed by lung sampling. The carcasses and lungs underwent macroscopical examination and were classified according to the score of pleurisy and lung samples were allocated into five groups, being: G0: score 0 - no lesions; G1: score 1; G2: score 2; G3: score 3; and G4: score 4. In total, 217 lung fragments were collected, for the histopathological evaluation and detection of the following respiratory pathogens: APP, Mhyo, and PM by qPCR. The results demonstrated that Mhyo and APP were the most prevalent etiological agents (single and co-identification) in lung samples, in different scores of pleurisies, while bronchopneumonia and bronchus-associated lymphoid tissue (BALT) hyperplasia lesions were the most frequent histopathological findings. Positive correlations were found between the quantification of APP DNA with 1) the score of pleurisy (R=0.254); 2) with the score of lung consolidation in all lung lobes (R=0.181 to R=0.329); and 3) with the score of lung consolidation in the entire lung (R=0.389). The study brings relevant information regarding the main bacterial pathogens associated with pleurisy in pigs and helps with understanding the relationship between the abovementioned pathogens and their impact on the respiratory health of pigs.

Feasibility of Near-Infrared Spectroscopy in the Classification of Pig Lung Lesions

Respiratory diseases significantly affect intensive pig farming, causing production losses and increased antimicrobial use. Accurate classification of lung lesions is crucial for effective diagnostics and disease management. The integration of non-destructive and rapid techniques would be beneficial to enhance overall efficiency in addressing these challenges. This study investigates the potential of near-infrared (NIR) spectroscopy in classifying pig lung tissues. The NIR spectra (908-1676 nm) of 101 lungs from weaned pigs were analyzed using a portable instrument and subjected to multivariate analysis. Two distinct discriminant models were developed to differentiate normal (N), congested (C), and pathological (P) lung tissues, as well as catarrhal bronchopneumonia (CBP), fibrinous pleuropneumonia (FPP), and interstitial pneumonia (IP) patterns. Overall, the model tailored for discriminating among pathological lesions demonstrated superior classification performances. Major challenges arose in categorizing C lungs, which exhibited a misclassification rate of 30% with N and P tissues, and FPP samples, with 30% incorrectly recognized as CBP samples. Conversely, IP and CBP lungs were all identified with accuracy, precision, and sensitivity higher than 90%. In conclusion, this study provides a promising proof of concept for using NIR spectroscopy to recognize and categorize pig lungs with different pathological lesions, offering prospects for efficient diagnostic strategies.

Susceptibility trends of swine respiratory pathogens from 2019 to 2022 to antimicrobials commonly used in Spain

BACKGROUND

Antimicrobial resistance is one of the most important health challenges in humans and animals. Antibiotic susceptibility determination is used to select the most suitable drug to treat animals according to its success probability following the European legislation in force for these drugs. We have studied the antibiotic susceptibility pattern (ASP) of Actinobacillus pleuropneumoniae (APP) and Pasteurella multocida (PM) isolates, collected during the period 2019-2022 in Spain. ASP was measured by determining minimum inhibitory concentration using standardized laboratory methods and its temporal trend was determined by logistic regression analysis of non-susceptible/susceptible isolates using clinical breakpoints.

RESULTS

It was not observed any significant temporal trends for susceptibility of Actinobacillus pleuropneumoniae to ceftiofur, florfenicol, sulfamethoxazole/trimethoprim, tulathromycin and tildipirosin during the study period (p > 0.05). Contrarily, a significant temporal trend (p < 0.05) was observed for quinolones (enrofloxacin and marbofloxacin), tetracyclines (doxycycline and oxyteracycline), amoxicillin, tiamulin and tilmicosin. On the other hand, it was not observed any significant temporal trends for susceptibility of Pasteurella multocida to quinolones (enrofloxacin and marbofloxacin), amoxicillin, ceftiofur, florfenicol and macrolides (tildipirosin, tulathromycin and tilmicosin) during the study period (p > 0.05). Contrarily, a significant temporal trend (p < 0.05) was observed for tetracyclines (oxyteracycline), tiamulin and sulfamethoxazole/trimethoprim.

CONCLUSIONS

In general terms, pig pathogens (APP and PM) involved in respiratory diseases analysed herein appeared to remain susceptible or tended to increase susceptibility to antimicrobials over the study period (2019-2022), but our data clearly showed a different pattern in the evolution of antimicrobial susceptibility for each combination of drug and microorganism. Our results highlight that the evolution of antimicrobial susceptibility must be studied in a case-by-case situation where generalization for drug families and bacteria is not possible even for bacteria located in the same ecological niche.

The economic impact of endemic respiratory disease in pigs and related interventions - a systematic review

BACKGROUND

Understanding the financial consequences of endemically prevalent pathogens within the porcine respiratory disease complex (PRDC) and the effects of interventions assists decision-making regarding disease prevention and control. The aim of this systematic review was to identify what economic studies have been carried out on infectious endemic respiratory disease in pigs, what methods are being used, and, when feasible, to identify the economic impacts of PRDC pathogens and the costs and benefits of interventions.

RESULTS

By following the PRISMA method, a total of 58 studies were deemed eligible for the purpose of this systematic review. Twenty-six studies used data derived from European countries, 18 from the US, 6 from Asia, 4 from Oceania, and 4 from other countries, i.e., Canada, Mexico, and Brazil. Main findings from selected publications were: (1) The studies mainly considered endemic scenarios on commercial fattening farms; (2) The porcine reproductive and respiratory syndrome virus was by far the most studied pathogen, followed by Mycoplasma hyopneumoniae, but the absence or presence of other endemic respiratory pathogens was often not verified or accounted for; (3) Most studies calculated the economic impact using primary production data, whereas twelve studies modelled the impact using secondary data only; (4) Seven different economic methods were applied across studies; (5) A large variation exists in the cost and revenue components considered in calculations, with feed costs and reduced carcass value included the most often; (6) The reported median economic impact of one or several co-existing respiratory pathogen(s) ranged from €1.70 to €8.90 per nursery pig, €2.30 to €15.35 per fattening pig, and €100 to €323 per sow per year; and (7) Vaccination was the most studied intervention, and the outcomes of all but three intervention-focused studies were neutral or positive.

CONCLUSION

The outcomes and discussion from this systematic review provide insight into the studies, their methods, the advantages and limitations of the existing research, and the reported impacts from the endemic respiratory disease complex for pig production systems worldwide. Future research should improve the consistency and comparability of economic assessments by ensuring the inclusion of high impact cost and revenue components and expressing results similarly.

Seroprevalence of Swine Influenza A Virus (swIAV) Infections in Commercial Farrow-to-Finish Pig Farms in Greece

Swine influenza is a highly contagious respiratory disease caused by influenza A virus infection. Pigs play an important role in the overall epidemiology of influenza because of their ability to transmit influenza viruses of avian and human origin, which plays a potential role in the emergence of zoonotic strains with pandemic potential. The aim of our study was to assess the seroprevalence of Swine Influenza Viruses (swIAVs) in commercial pig farms in Greece. A total of 1416 blood samples were collected from breeding animals (gilts and sows) and pigs aged 3 weeks to market age from 40 different swIAV vaccinated and unvaccinated commercial farrow-to-finish pig farms. For the detection of anti-SIV antibodies, sera were analyzed using an indirect ELISA kit CIVTEST SUIS INFLUENZA®, Hipra (Amer, Spain). Of the total 1416 animals tested, 498 were seropositive, indicating that the virus circulates in both vaccinated (54% seroprevalence) and unvaccinated Greek pig farms (23% seroprevalence). In addition, maternally derived antibody (MDA) levels were lower in pigs at 4 and 7 weeks of age in unvaccinated farms than in vaccinated farms. In conclusion, our results underscore the importance of vaccination as an effective tool for the prevention of swIAV infections in commercial farrow-to-finish pig farms.

Complex interplay between PRRSV-1 genetic diversity, coinfections and antimicrobial use influences performance parameters in post-weaning pigs

Porcine reproductive and respiratory syndrome (PRRS) is one of the main diseases of pigs, leading to large economic losses in swine production worldwide. PRRSV high mutation rate and low cross-protection between strains make PRRS control challenging. Through a semi-longitudinal approach, we analysed the relationships among performance parameters, PRRSV-1 genetic diversity, coinfections and antimicrobial use (AMU) in pig nurseries. We collected data over the course of five years in five PRRS-positive nurseries belonging to an Italian multisite operation, for a total of 86 batches and over 200,000 weaners involved. The farm experienced a severe PRRS outbreak in the farrowing unit at the onset of the study, but despite adopting vaccination of all sows, batch-level losses in nurseries in the following years remained constantly high (mean±SE: 11.3 ± 0.5 %). Consistently with previous studies, our phylogenetic analysis of ORF 7 sequences highlighted the peculiarity of strains circulating in Italy. Greater genetic distances between the strain circulating in a weaners' batch and strains from the farrowing unit and the previous batch were associated with increased mortality (p < 0.0001). All the respiratory and enteric coinfections contributed to an increase in losses (all p < 0.026), with secondary infections by Streptococcus suis and enteric bacteria also inducing an increase in AMU (both p < 0.041). Our findings highlight that relying solely on sows' vaccination is insufficient to contain PRRS losses, and the implementation of rigorous biosecurity measures is pivotal to limit PRRSV circulation among pig flows and consequently minimise the risk of exposure to genetically diverse strains that would increase production costs.

Porcine circovirus type 2 and porcine reproductive and respiratory syndrome virus alone or associated are frequent intralesional detected viruses in porcine respiratory disease complex cases in Northern Italy

Methods

This study aimed to examine the pathological impact of Porcine Circovirus type 2 (PCV2) and Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) through histological and immunohistochemical analysis of 79 cases of Porcine Respiratory Disease Complex (PRDC) collected from 22 farms in Northern Italy. Lung tissue and several lymphoid organ samples were deployed to associate PCV2-positive stain with Circovirus-associated Diseases (PCVD).

Results

The most common lung lesion observed was interstitial pneumonia, alone or combined with bronchopneumonia. By immunohistochemistry, 44 lungs (55.7%) tested positive for PCV2, 34 (43.0%) for PRRSV, 16 (20.3%) for both viruses and in 17 cases (21.5%) neither virus was detected. Twenty-eight out of 44 (63.6%) PCV2-positive cases had lymphoid depletion or granulomatous inflammation in at least one of the lymphoid tissues examined; thus, they were classified as PCV2 Systemic Diseases (PCV2-SD). In the remaining 16 out of 44 cases (36.4%), PCV2-positive lung lesions were associated with hyperplastic or normal lymphoid tissues, which showed PCV2-positive centrofollicular dendritic cells in at least one of the lymphoid tissues examined. Therefore, these cases were classified as PRDC/PCV2-positive. In the PCV2-positive animals, 42.9% of the PCV2-SD cases (12/28) showed immunohistochemistry (IHC) positivity for PRRSV in the lung tissue, while 25.0% of PRDC/PCV2-positive cases (4/16) showed double positivity for PCV2 and PRRSV.

Discussion

In light of the caseload presented in this study, characterized by the high proportion of PCV2-SD cases alongside the overall respiratory symptomatology, it is imperative to emphasize the crucial role of a comprehensive sampling protocol. This is critical to avoid underestimating the harm caused by PCV2 in farms, particularly with respect to the systemic form of the disease. PCV2 and PRRSV remain the primary infections associated with PRDC in Italy that can significantly impact farm health and co-infections in the field can worsen the pathology, thus the selection of appropriate preventive measures is critical.

A Recombinant Chimera Vaccine Composed of LTB and Mycoplasma hyopneumoniae Antigens P97R1, mhp390 and P46 Elicits Cellular Immunologic Response in Mice

Mycoplasma hyopneumoniae is the etiological agent of porcine enzootic pneumonia (EP), leading to a mild and chronic pneumonia in swine. Relative control has been attained through active vaccination programs, but porcine enzootic pneumonia remains a significant economic challenge in the swine industry. Cellular immunity plays a key role in the prevention and control of porcine enzootic pneumonia. Therefore, the development of a more efficient vaccine that confers a strong immunity against M. hyopneumoniae is necessary. In this study, a multi-antigen chimera (L9m6) was constructed by combining the heat-labile enterotoxin B subunit (LTB) with three antigens of M. hyopneumoniae (P97R1, mhp390, and P46), and its immunogenic and antigenic properties were assessed in a murine model. In addition, we compared the effect of individual administration and multiple-fusion of these antigens. The chimeric multi-fusion vaccine induced significant cellular immune responses and high production of IgG and IgM antibodies against M. hyopneumoniae. Collectively, our data suggested that rL9m6 chimera exhibits potential as a viable vaccine candidate for the prevention and control of porcine enzootic pneumonia.

Comparing Visual-Only and Visual-Palpation Post-Mortem Lung Scoring Systems in Slaughtering Pigs

Respiratory diseases continue to pose significant challenges in pig production, and the assessment of lung lesions at the abattoir can provide valuable data for epidemiological investigations and disease surveillance. The evaluation of lung lesions at slaughter is a relatively simple, fast, and straightforward process but variations arising from different abattoirs, observers, and scoring methods can introduce uncertainty; moreover, the presence of multiple scoring systems complicates the comparisons of different studies, and currently, there are limited studies that compare these systems among each other. The objective of this study was to compare validated, simplified, and standardized schemes for assessing surface-related lung lesions in slaughtered pigs and analyze their reliability under field conditions. This study was conducted in a high-throughput abattoir in Italy, where two different scoring methods (Madec and Blaha) were benchmarked using 637 plucks. Statistical analysis revealed a good agreement between the two methods when severe or medium lesions were observed; however, their ability to accurately identify healthy lungs and minor injuries diverged significantly. These findings demonstrate that the Blaha method is more suitable for routine surveillance of swine respiratory diseases, whereas the Madec method can give more detailed and reliable results for the respiratory and welfare status of the animals at the farm level.

Association between Enzootic Pneumonia-like Lung Lesions and Carcass Quality and Meat pH Value in Slaughter Pigs

Although the prevalence of respiratory diseases in slaughter pigs ranges from 19% to 74% and continues to be an important concern for swine herds worldwide, only a few studies have investigated the relationship between respiratory disease and pork quality. The general aim of this study was to investigate associations between the prevalence and severity of enzootic pneumonia-like lesions in Polish slaughter pigs on different carcass and meat-quality characteristics at the animal and herd levels. The average prevalence of bronchopneumonic lungs with different degrees of lesions was 94.57%. The majority of lesions indicated the acute stage of enzootic pneumonia. Our results indicate a statistically significant interaction between the mean weight of carcasses depending on the extent of the lesions (p = 0.04) at the animal level. The correlation between meatiness and severity of lung lesions was r = -0.25 (p = 0.00). The correlation between the extent of lung lesions and pH₄₅ value was r = -0.17 (p = 0.005) on the animal level and r = -0.63 (p = 0.017) at the herd level. This implies that lung lesions in slaughter pigs negatively influence not only animal health and welfare, but also carcass quality.

Simultaneous co-infection with swine influenza A and porcine reproductive and respiratory syndrome viruses potentiates adaptive immune responses

Porcine respiratory disease is multifactorial and most commonly involves pathogen co-infections. Major contributors include swine influenza A (swIAV) and porcine reproductive and respiratory syndrome (PRRSV) viruses. Experimental co-infection studies with these two viruses have shown that clinical outcomes can be exacerbated, but how innate and adaptive immune responses contribute to pathogenesis and pathogen control has not been thoroughly evaluated. We investigated immune responses following experimental simultaneous co-infection of pigs with swIAV H3N2 and PRRSV-2. Our results indicated that clinical disease was not significantly exacerbated, and swIAV H3N2 viral load was reduced in the lung of the co-infected animals. PRRSV-2/swIAV H3N2 co-infection did not impair the development of virus-specific adaptive immune responses. swIAV H3N2-specific IgG serum titers and PRRSV-2-specific CD8β⁺ T-cell responses in blood were enhanced. Higher proportions of polyfunctional CD8β⁺ T-cell subset in both blood and lung washes were found in PRRSV-2/swIAV H3N2 co-infected animals compared to the single-infected groups. Our findings provide evidence that systemic and local host immune responses are not negatively affected by simultaneous swIAV H3N2/PRRSV-2 co-infection, raising questions as to the mechanisms involved in disease modulation.

Associations between Pleurisy and the Main Bacterial Pathogens of the Porcine Respiratory Diseases Complex (PRDC)

Porcine Respiratory Diseases Complex (PRDC) is a multifactorial disease that involves several bacterial pathogens, including Mycoplasma hyopneumoniae (M. hyopneumoniae), Actinobacillus pleuropneumoniae (A. pleuropneumoniae), Pasteurella multocida (P. multocida), Glaesserella parasuis (G. parasuis), and Streptococcus suis (S. suis). In pigs, the infection may cause lesions such pleurisy, which can lead to carcass condemnation. Hence, 1015 carcasses were selected from three different commercial pig farms, where the respiratory conditions were evaluated using slaughterhouse pleurisy evaluation system (SPES) and classified into five groups. In total, 106 pleural and lung fragments were collected for qPCR testing to identify the five abovementioned pathogens. A moderate correlation between the severity of the lesions and the presence of P. multocida (R = 0.38) and A. pleuropneumoniae (R = 0.28) was observed. Concerning the lung samples, the severity of the lesions was moderately correlated with the presence of P. multocida (R = 0.43) and M. hyopneumoniae (R = 0.35). Moreover, there was a strong correlation between the presence of P. multocida and M.hyopneumoniae in the pleura (R = 0.82). Finally, this approach may be a useful tool to identify and quantify causative agents of PRDC using qPCR, providing a comprehensive evaluation of its relevance, strength, and potential application in the field as a surveillance tool for veterinarians.

Evaluation of early single dose vaccination on swine influenza A virus transmission in piglets: From experimental data to mechanistic modelling

Swine influenza A virus (swIAV) is a major pathogen affecting pigs with a huge economic impact and potentially zoonotic. Epidemiological studies in endemically infected farms permitted to identify critical factors favoring on-farm persistence, among which maternally-derived antibodies (MDAs). Vaccination is commonly practiced in breeding herds and might be used for immunization of growing pigs at weaning. Althoughinterference between MDAs and vaccination was reported in young piglets, its impact on swIAV transmission was not yet quantified. To this aim, this study reports on a transmission experiment in piglets with or without MDAs, vaccinated with a single dose injection at four weeks of age, and challenged 17 days post-vaccination. To transpose small-scale experiments to real-life situation, estimated parameters were used in a simulation tool to assess their influence at the herd level. Based on a thorough follow-up of the infection chain during the experiment, the transmission of the swIAV challenge strain was highly dependent on the MDA status of the pigs when vaccinated. MDA-positive vaccinated animals showed a direct transmission rate 3.6-fold higher than the one obtained in vaccinated animals without MDAs, estimated to 1.2. Vaccination nevertheless reduced significantly the contribution of airborne transmission when compared with previous estimates obtained in unvaccinated animals. The integration of parameter estimates in a large-scale simulation model, representing a typical farrow-to-finish pig herd, evidenced an extended persistence of viral spread when vaccination of sows and single dose vaccination of piglets was hypothesized. When extinction was quasi-systematic at year 5 post-introduction in the absence of sow vaccination but with single dose early vaccination of piglets, the extinction probability fell down to 33% when batch-to-batch vaccination was implemented both in breeding herd and weaned piglets. These results shed light on a potential adverse effect of single dose vaccination in MDA-positive piglets, which might lead to longer persistence of the SwIAV at the herd level.

Co-infections of respiratory pathogens and gastrointestinal parasites in smallholder pig production systems in Uganda

A cross-sectional study was conducted to identify factors for infections of pigs with key respiratory pathogens: porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PPRSv), Mycoplasma hyopneumoniae (M. hyo), Actinobacillus pleuropneumoniae (App), and gastrointestinal (GI) parasites in Uganda. A structured questionnaire was used to collect data on management practices associated with infections. Ninety (90) farms and 259 pigs were sampled. Sera were screened against 4 pathogens using commercial ELISA tests. The Baerman's method was used to identify parasite species in faecal samples. Logistic regression was done to identify risk factors for infections. Results showed individual animal seroprevalence of PCV2 was 6.9% (95% CI 3.7-11.1), PRRSv 13.8% (95% CI 8.8-19.6), M. hyo 6.4% (95% CI 3.5-10.5), and App 30.4% (95% CI 24.8-36.5). The prevalence of Ascaris spp. was 12.7% (95% CI 8.6-16.8), Strongyles spp was 16.2% (95% CI 11.7-20.7), and Eimeria spp. was 56.4% (95% CI 50.3-62.4). Pigs infested with Ascaris spp. were more likely to test positive to PCV2, odds ratio (OR) 1.86 (CI 1.31-2.60; p = 0.0002). For M. hyo, infection with Strongyles spp. was a risk factor (OR 12.9, p < 0.001). Pigs that had Strongyles and Ascaris spp. Infections (ORs 3.5 and 3.4, p < 0.001 respectively) were likely to have co-infections. The model showed that use of cement, elevated floor, and limiting contacts with outside pigs were protective while using mud and helminth infestations increased risks of co-infections. This study provided evidence that improved housing and biosecurity are critical in reducing pathogen incidence in herds.

Genetic diversity of Mycoplasma hyopneumoniae in finishing pigs in Minas Gerais

ABSTRACT: Mycoplasma hyopneumoniae is one of the most challenging respiratory pathogens involved with swine pneumonia worldwide, responsible for a chronic infection with high morbidity, which predisposes secondary bacterial infections in growing and finishing pigs. Advances in diagnostic techniques allowed identification of genetic characteristics associated with high antigenic and proteomic variability among bacterial strains. This study aimed to evaluate the genetic diversity of M. hyopneumoniae strains in lungs with pneumonic lesions obtained from 52 pig farms located in Minas Gerais, one of the largest swine production states in Brazil. Genotyping was performed using multilocus variable number of tandem repeat (VNTR) analysis (MLVA), targeting two loci encoding P97 and P146 adhesins VNTR. The results showed that this agent is widely disseminated in pig farms and there is a high polymorphism of M. hyopneumoniae variants circulating in the state of Minas Gerais. Different M. hyopneumoniae genotypes are randomly distributed in several regions of the state, with no specific geographic population structure pattern. M. hyopneumoniae association with viral agents was sporadic (3.17% with Influenza A and 1.9% with PCV2).

Review on the methodology to assess respiratory tract lesions in pigs and their production impact

Porcine respiratory disease is one of the most important health problems in pig production worldwide. Cranioventral pulmonary consolidation (CVPC) and pleurisy are the two most common lesions in the respiratory tract of slaughtered pigs. The present review paper discusses pathogens involved in the lesions, lesion prevalence, scoring systems, advantages and disadvantages of slaughterhouse examination, and the impact of CVPC and pleurisy on performance, carcass, and meat quality. Cranioventral pulmonary consolidation and pleurisy in slaughter pigs are characteristic for infections with Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae, respectively, although other pathogens may cause similar lesions and/or be involved in their development. The overall prevalence of CVPC and pleurisy in slaughter pigs are still high, being the prevalence of CVPC generally higher than that of chronic pleurisy. The advantages and disadvantages of slaughterhouse examination are discussed in relation to practical aspects, the assessment of lesions, the number and representativeness of the examined animals and the interpretation and value of the results for the stakeholders. The main scoring methods for CVPC and pleurisy are shortly reviewed. In general, scoring methods can be applied rapidly and easily, although significant variation due to abattoir and observer remains. Artificial intelligence-based technologies that automatically score lesions and facilitate processing of data may aid solving these problems. Cranioventral pulmonary consolidation and pleurisy have a major negative impact on pig performance, and the effects increase the extension of the lesions and/or presence of multiple lesions. The performance losses caused by these lesions, however, vary significantly between studies and farms, possibly due to differences in study population and used methodology. Both lesions also have a negative impact on different carcass and meat quality parameters, leading to increased risk for poor processing and storage of the carcasses. Monitoring lung lesions of slaughter pigs should be optimized and implemented routinely; however, it is recommended to complement this information with farm data and laboratory results for specific pathogens.

Evaluation of Intradermal PRRSV MLV Vaccination of Suckling Piglets on Health and Performance Parameters under Field Conditions

Porcine reproductive and respiratory syndrome virus (PRRSV) causes respiratory disease in weaning and growing pigs. A vaccination against PRRSV is one of the most important control measures. This trial aimed to evaluate the effect of the intradermal (ID) administration of a PRRSV-1 modified live virus (MLV) vaccine in comparison to the intramuscular (IM) administration on the piglets’ health and performance. A total of 187 suckling piglets of a PRRSV-positive commercial farrow-to-finish farm were assigned to four groups: group A—PRRSV ID, group B—PRRSV IM, group C—control ID, and group D—control IM. At 2 weeks of age, all the study piglets were either vaccinated with a PRRSV-1 MLV vaccine or injected with the vaccine adjuvant (controls). The collected blood serum samples were tested by ELISA and qRT-PCR. The side effects, body weight (BW), average daily gain (ADG), mortality rate, and lung and pleurisy lesions scores (LLS, PLS) were also recorded. The ELISA results indicated that the vaccination induced an important seroconversion at 4 and 7 weeks. Significant differences in the qRT-PCR results were noticed only at 10 weeks in group A vs. group C (p < 0.01) and group B vs. group C (p < 0.05). High viral loads, as evidenced by the qRT-PCR Ct values, were noticed in animals of both non-vaccinated groups at 7, 10, and 13 weeks. An ID vaccination has a positive impact on the BW at the piglets’ slaughter, while both an ID and IM vaccination had a positive impact on the ADG. The mortality rate was lower in vaccinated groups at the finishing stage. The LLS and PLS were significantly lower in the vaccinated groups. In conclusion, our study demonstrated that the ID vaccination of suckling piglets with a PRRSV-1 MLV vaccine has a positive effect on the piglets’ health and performance, including an improved BW and a lower LLS and PLS index at their slaughter, as well as a decreased mortality rate at the growing/finishing stage.

Porcine respiratory disease complex: Dynamics of polymicrobial infections and management strategies after the introduction of the African swine fever

A few decades ago, porcine respiratory disease complex (PRDC) exerted a major economic impact on the global swine industry, particularly due to the adoption of intensive farming by the latter during the 1980's. Since then, the emerging of porcine reproductive and respiratory syndrome virus (PRRSV) and of porcine circovirus type 2 (PCV2) as major immunosuppressive viruses led to an interaction with other endemic pathogens (e.g., Mycoplasma hyopneumoniae, Actinobacillus pleuropneumoniae, Streptococcus suis, etc.) in swine farms, thereby exacerbating the endemic clinical diseases. We herein, review and discuss various dynamic polymicrobial infections among selected swine pathogens. Traditional biosecurity management strategies through multisite production, parity segregation, batch production, the adoption of all-in all-out production systems, specific vaccination and medication protocols for the prevention and control (or even eradication) of swine diseases are also recommended. After the introduction of the African swine fever (ASF), particularly in Asian countries, new normal management strategies minimizing pig contact by employing automatic feeding systems, artificial intelligence, and robotic farming and reducing the numbers of vaccines are suggested. Re-emergence of existing swine pathogens such as PRRSV or PCV2, or elimination of some pathogens may occur after the ASF-induced depopulation. ASF-associated repopulating strategies are, therefore, essential for the establishment of food security. The "repopulate swine farm" policy and the strict biosecurity management (without the use of ASF vaccines) are, herein, discussed for the sustainable management of small-to-medium pig farms, as these happen to be the most potential sources of an ASF re-occurrence. Finally, the ASF disruption has caused the swine industry to rapidly transform itself. Artificial intelligence and smart farming have gained tremendous attention as promising tools capable of resolving challenges in intensive swine farming and enhancing the farms' productivity and efficiency without compromising the strict biosecurity required during the ongoing ASF era.

Polymerase chain reaction-based detection of coinfecting DNA viruses in Vietnamese pigs in 2017 and 2021

Background and Aim: Many studies have reported on the phenomenon of co-infections involving two or more pathogens (bacteria or viruses) over the past few years. However, very few studies on this issue were conducted in Vietnam. Therefore, this study aimed to determine the circulation of single and multiple porcine parvovirus (PPV) (e.g., PPV1, PPV2, PPV3, and PPV4), porcine bocavirus (PBoV), and torque teno virus (TTV) (TTV1 and TTV2) infections in Vietnamese pigs. Materials and Methods: A total of 174 porcine circovirus 2-positive samples from pigs (n = 86 for 2017 and n = 88 for 2021), including from the sera and internal organs, across 11 provinces were examined by polymerase chain reaction. Results: This study demonstrated the wide distribution of DNA viruses among pig farms in Vietnam in 2021, with the detection rate for PPV ranging from 3.4% to 27.3% among PPV1-PPV4. Moreover, the detection rates of TTV genotypes were confirmed to be 14.8% (TTV1) and 63.6% (TTV2), respectively, and the positive rate of PBoV was 65.9%. The most frequent combinations were double and triple infections. Double infection was found in 16/86 (18.6%) in 2017 and 26/88 (29.5%) in 2021, while triple infection was found at 19/86 (22.1%) in 2017 and 26/88 (29.5%) in 2021. The incidence of simultaneous detection of more than three viruses was low. Conclusion: These results provide at least partial information about the occurrence of three viruses, including PPV (including PPV1 to 4), PBoV, and TTV (TTV1 and TTV2), in pigs. Determination of particular viruses in pigs will help to prevent the porcine respiratory disease complex caused by DNA viruses in Vietnamese pigs in the future.

Investigation and analysis of etiology associated with porcine respiratory disease complex in China from 2017 to 2021

Porcine respiratory diseases complex (PRDC) is a highly serious threat to the pig industry. In the present study, we investigated and analyzed the etiology associated with PRDC and explored the role of viruses in respiratory bacterial infections. From 2017 to 2021, clinical samples were collected from 1,307 pigs with typical respiratory symptoms in 269 farms in China and screened for pathogens related to PRDC by PCR and bacterial isolation. The results indicated that PRRSV (41.16%, 95%CI: 38.49~43.83%), PCV2 (21.58%,95%CI: 19.35~23.81%), S. suis (63.50%, 95%CI: 60.89~66.11%), and G. parasuis (28.54%, 95%CI: 26.09~30.99%) were the most commonly detected pathogens in pigs with PRDC in China. The dominant epidemic serotypes (serogroups) of S. suis, G. parasuis, and P. multocida were serotype 2, serotype 1, and capsular serogroups D, respectively. Pigs of different ages exhibited different susceptibilities to these pathogens, e.g., PRRSV, PCV2, and G. parasuis had the highest detection rates in nursery pigs, whereas fattening pigs had the highest detection rates of P. multocida and A. pleuropneumoniae. Among the 1,307 pigs, the detection rates of S. suis, G. parasuis, P. multocida, and B. bronchiseptica were higher in virus-positive pigs, especially G. parasuis and P. multocida were significantly (p < 0.01) higher than in virus-negative pigs. In addition, a strong positive correlation was found between coinfection by PRRSV and G. parasuis (OR = 2.33, 95%CI: 1.12~2.14), PRRSV and P. multocida (OR = 1.55, 95%CI: 1.12~2.14), PCV2 and P. multocida (OR = 2.27, 95%CI: 1.33~3.87), PRRSV-PCV2 and S. suis (OR = 1.83, 95%CI: 1.29~2.60), PRRSV-PCV2 and G. parasuis (OR = 3.39, 95%CI: 2.42~4.74), and PRRSV-PCV2 and P. multocida (OR = 2.09, 95%CI: 1.46~3.00). In summary, PRRSV, PCV2, S. suis, and G. parasuis were the major pathogens in pigs with PRDC, and coinfections of two or more PRDC-related pathogens with strong positive correlations were common in China, such as PRRSV and G. parasuis, PRRSV and P. multocida, PCV2 and P. multocida, and also PRRSV-PCV2 and G. parasuis and PRRSV-PCV2 and P. multocida.

Characteristics of Mycoplasma hyopneumoniae Strain ES-2 Isolated From Chinese Native Black Pig Lungs

Mycoplasma hyopneumoniae is the primary pathogen of swine enzootic pneumonia and causes great economic losses to the swine industry worldwide. In China, M. hyopneumoniae seriously hinders the healthy development of the native black pigs. To prevent and treat porcine respiratory disease caused by M. hyopneumoniae, the characteristics of M. hyopneumoniae strain ES-2 isolated from Chinese native black pig lungs with gross lesions at post-mortem were studied for the first time in this study. Strain ES-2 cell was round or oval cells and most sensitive to kanamycin. The diameters of most strain ES-2 cells ranged from 0.4 to 1.0 μm with maximum viability of 1010 CCU/ml. Experimental challenge of animals with strain ES-2 showed respiratory disease could be reproduced, with pneumonic lung lesions evident. Comparative genomics analysis identified that 2 genes are specific to pathogenic M. hyopneumoniae strains, which may be predicted to be a molecular marker. These findings suggest that the study on the characteristics of M. hyopneumoniae strain ES-2 will guide the rapid and accurate drug use in the clinic, and develop a theoretical foundation for accurately diagnosing and treating the infection caused by pathogenic M. hyopneumoniae.

A total infectome approach to understand the etiology of infectious disease in pigs

BACKGROUND

The global pork industry is continuously affected by infectious diseases that can result in large-scale mortality, trade restrictions, and major reductions in production. Nevertheless, the cause of many infectious diseases in pigs remains unclear, largely because commonly used diagnostic tools fail to capture the full diversity of potential pathogens and because pathogen co-infection is common.

RESULTS

We used a meta-transcriptomic approach to systematically characterize the pathogens in 136 clinical cases representing different disease syndromes in pigs, as well as in 12 non-diseased controls. This enabled us to simultaneously determine the diversity, abundance, genomic information, and detailed epidemiological history of a wide range of potential pathogens. We identified 34 species of RNA viruses, nine species of DNA viruses, seven species of bacteria, and three species of fungi, including two novel divergent members of the genus Pneumocystis. While most of these pathogens were only apparent in diseased animals or were at higher abundance in diseased animals than in healthy animals, others were present in healthy controls, suggesting opportunistic infections. Importantly, most of the cases examined here were characterized by co-infection with more than two species of viral, bacterial, or fungal pathogens, some with highly correlated occurrence and abundance levels. Examination of clinical signs and necropsy results in the context of relevant pathogens revealed that a multiple-pathogen model was better associated with the data than a single-pathogen model was.

CONCLUSIONS

Our data demonstrate that most of the pig diseases examined were better explained by the presence of multiple rather than single pathogens and that infection with one pathogen can facilitate infection or increase the prevalence/abundance of another. Consequently, it is generally preferable to consider the cause of a disease based on a panel of co-infecting pathogens rather than on individual infectious agents. Video abstract.

Lungworms (Metastrongylus spp.) demonstrated in domestic pigs with respiratory disease: was there a clinical relevance?

Background

An outdoor pig herd was affected by severe respiratory disease in one out of three pastures. At necropsy, Mycoplasma hyopneumoniae and Pasteurella multocida were detected in the lungs, as well as the lung worm Metastrongylus apri. The life cycle of Metastrongylus spp. includes earthworms as intermediate hosts, and since domestic pigs mainly are reared indoors, lungworm infections have not been diagnosed in domestic pigs in Sweden for decades, not even in pigs reared outdoors. Therefore, this disease outbreak was scrutinised from the view of validating the impact of Metastrongylus spp.

Results

At the time of the disease outbreak, neither eggs of Metastrongylus spp., Trichuris suis nor Ascaris suum were detected in faeces of pigs aged ten weeks. In contrast, five-months-old pigs at the pasture with respiratory disease shed up to 3800 eggs per gram (Epg) of Ascaris suum and up to 1100 Epg of Trichuris suis, whereas eggs of these parasites were not demonstrated in healthy pigs aged six months at another pasture. Low numbers of eggs from Metastrongylus spp. (< 150 Epg) were seen in faecal samples from both these age categories. At slaughter, seven weeks later, ten normal weighted pigs in the preceding healthy batch were compared with ten normal weighted and five small pigs from the affected batch. Healing Mycoplasma-like pneumonic lesions were seen in all groups. All small pigs shed eggs of Ascaris suum in the faeces, compared to around 50% of the larger pigs. Metastrongylus spp. were demonstrated in 13 of the 25 pigs (52%), representing all groups included.

Conclusion

As Metastrongylus spp. were demonstrated regardless of health status, and also in another healthy outdoor herd, the impact of Metastrongylus spp. on the outbreak of respiratory disease was depreciated. Instead, a possible association with a high burden of Ascaris suum was suggested to have preceded the severe outbreak with respiratory disease in the affected herd. Further, it was concluded that Metastrongylus spp. will escape detection at routine meat inspections made at slaughterhouses, and as they appeared to generally not induce clinical signs of respiratory disease Metastrongylus spp. may be more common in outdoor production than previously believed.

Cross-sectional study on the in-herd prevalence of Mycoplasma hyopneumoniae at different stages of pig production

BACKGROUND

A cross-sectional study was carried out to assess the prevalence of Mycoplasma hyopneumoniae infections before vaccination in 3-week-old piglets and to gain information about infection dynamics.

METHODS

In 13 German and three Austrian farms with a known history of enzootic pneumonia, 790 piglets and 158 sows were sampled (blood samples, tracheobronchial swabs [TBS] [piglets], laryngeal swabs [LS] [sows]), and 525 pen-based oral fluids (OFs) were collected in growing and fattening pigs. Laboratory diagnostics included enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (PCR) analyses.

RESULTS

Antibodies to M. hyopneumoniae were present in 87.5 per cent of all herds. Seroprevalence ranged from 0.0 to 100.0 per cent and 0.0 to 88.0 per cent in sows and piglets, respectively. M. hyopneumoniae-deoxyribonucleic acid (DNA) was present in 3.8 and 0.4 per cent of LS and TBS, respectively. Gilts had a 10.9 times higher chance being M. hyopneumoniae PCR-positive than older sows. In 75.0 per cent of all farms, M. hyopneumoniae-DNA was present in OFs. Detection rate was significantly higher in OFs of 20-week-old than in younger pigs (p < 0.001).

CONCLUSION

Results indicate that M. hyopneumoniae infections of the lower respiratory tract in piglets are rare but highlight the role of gilts in maintaining infection in the herd. Collecting OFs seems promising for surveillance, if coughing occurs simultaneously.

Assessment of Lung Disease in Finishing Pigs at Slaughter: Pulmonary Lesions and Implications on Productivity Parameters

Simple Summary

Examination of lung lesions at slaughterhouses provides important information regarding swine respiratory disease presence in farms worldwide. This study evaluated pulmonary lesions in pigs at slaughter and assessed their effect on productive parameters. We observed a high occurrence (73.1%) of lung lesions in a cohort of 108 pigs; these lesions were associated with primary bacterial disease or a combination of bacterial and viral pathogens. The animals with more severe lesions had lower weight gain, remained at the farm longer, and were exposed to reinfection. Through laboratory tests, we demonstrated coinfections between Mycoplasma hyopneumoniae, porcine circovirus type 2, and porcine reproductive and respiratory syndrome virus in affected lungs. We suggest that pigs that do not reach the desired weight at slaughter age should be sent to slaughter regardless, thus avoiding economic losses due to suboptimal productive parameters and aggravated respiratory disease by reinfection.

Abstract

Swine respiratory disease is associated with productive losses. We evaluated the prevalence of lung lesions with an emphasis on Mycoplasma hyopneumoniae (Mh), porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV), as well as the impact on productive parameters in 108 finishing pigs at slaughter. Pathologic, immunohistochemical (IHC) and serologic analyses were performed. Pneumonic processes were observed in 73.1% of the animals. They mainly consisted of cranioventral bronchopneumonia (CBP) (46.3%) and pleuritis (17.6%). Microscopically, bronchointerstitial pneumonia (67.4%) was common and was occasionally combined (27.9%) with interstitial pneumonia (IP). Mh and PCV2-antigens were detected in bronchointerstitial pneumonia (70.7%) and IP cases (33.3%). There were low titers against Mh (18%) and high titers against PRRSV (100%) and PCV2 (65%). Animals with CBP remained at the farm longer; those with >10% of lung parenchyma involvement were sent later (208.8 days old) and had a lower average carcass weight (74.1 kg) and a lower daily weight gain (500.8 gr/day) compared with animals without lesions (567.2 gr/day, 77.7 kg, 200.8 days old). We suggest that animals that do not reach the weight at slaughter should be sent to slaughter regardless to avoid further negative impacts of respiratory disease in productive parameters.

The epidemiology of swine influenza

Globally swine influenza is one of the most important diseases of the pig industry, with various subtypes of swine influenza virus co-circulating in the field. Swine influenza can not only cause large economic losses for the pig industry but can also lead to epidemics or pandemics in the human population. We provide an overview of the pathogenic characteristics of the disease, diagnosis, risk factors for the occurrence on pig farms, impact on pigs and humans and methods to control it. This review is designed to promote understanding of the epidemiology of swine influenza which will benefit the control of the disease in both pigs and humans.

The Role of Pathology in the Diagnosis of Swine Respiratory Disease

The definition “porcine respiratory disease complex” (PRDC) is used to indicate the current approach for presenting respiratory pathology in modern pig farming. PRDC includes pneumonias with variable pictures, mixed with both aerogenous and hematogenous forms with variable etiology, often multimicrobial, and influenced by environmental and management factors. The notion that many etiological agents of swine respiratory pathology are ubiquitous in the airways is commonly understood; however, their isolation or identification is not always associable with the current pathology. In this complex context, lung lesions registered at slaughterhouse or during necropsy, and supplemented by histological investigations, must be considered as powerful tools for assigning a prominent role to etiologic agents. In recent years, the goal of colocalizing causative agents with the lesions they produce has been frequently applied, and valid examples in routine diagnostics are those that indicate pulmonary involvement during porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) infections.

Successive Inoculations of Pigs with Porcine Reproductive and Respiratory Syndrome Virus 1 (PRRSV-1) and Swine H1N2 Influenza Virus Suggest a Mutual Interference between the Two Viral Infections

Porcine reproductive and respiratory syndrome virus (PRRSV) and swine influenza A virus (swIAV) are major pathogens of the porcine respiratory disease complex, but little is known on their interaction in super-infected pigs. In this study, we investigated clinical, virological and immunological outcomes of successive infections with PRRSV-1 and H1N2 swIAV. Twenty-four specific pathogen-free piglets were distributed into four groups and inoculated either with PRRSV at study day (SD) 0, or with swIAV at SD8, or with PRRSV and swIAV one week apart at SD0 and SD8, respectively, or mock-inoculated. In PRRSV/swIAV group, the clinical signs usually observed after swIAV infection were attenuated while higher levels of anti-swIAV antibodies were measured in lungs. Concurrently, PRRSV multiplication in lungs was significantly affected by swIAV infection, whereas the cell-mediated immune response specific to PRRSV was detected earlier in blood, as compared to PRRSV group. Moreover, levels of interferon (IFN)-α measured from SD9 in the blood of super-infected pigs were lower than those measured in the swIAV group, but higher than in the PRRSV group at the same time. Correlation analyses suggested an important role of IFN-α in the two-way interference highlighted between both viral infections.

Correlations between lung pneumonic lesions and serologic status for key respiratory pathogens in slaughtered pigs in northern Uganda

Background

A cross-sectional study of slaughtered pigs was conducted in Lira district, Uganda, to (1) determine the prevalence and severity of pneumonia and (2) establish relationships between pneumonia types and the serological status for key respiratory pathogens. Using enzyme-linked immunosorbent assays (ELISAs), sera were screened for antibodies against Mycoplasma hyopneumoniae (M. hyo), Actinobacillus pleuropneumoniae (App), porcine reproductive and respiratory syndrome virus (PRRSv) and porcine circovirus type 2 (PCV2). Postmortem, lungs were grossly scored for pneumonia types and pneumonic lesions. Pneumonia types were characterized as catarrhal purulent bronchopneumonia (CPBP), pleuropneumonia (PLP) and pleuritis. The percent of lung surface affected by pneumonia was determined by estimating the affected surface area of each lung lobe. Each lobe was assigned scores based on the approximate volume represented and the total percentage of lung surface affected obtained as a sum of individual lobe scores. Metastrongylus spp. helminth infection was determined by examining lungs for gross presence or absence. RStudio was used for data analysis and presentation. Wilcoxon rank sum tests were used to compare median pneumonia lesion scores and serostatus for each studied pathogen. An ordinal logistic regression model was fitted to evaluate the odds of multiple pneumonia, with pathogen serostatus and Metastrongylus spp. infection as predictors.

Results

One hundred sixty-seven (n = 167) lungs were examined for pneumonic lesions. The prevalences of CPBP, PLP and pleuritis were 29.9% (95% CI 22.9–36.9), 74.2% (95% CI 67.5–80.9) and 17.3% (95% CI 22.4–36.3), respectively. The true prevalence of PCV2 was 9.7% (95% CI 4.5–16.8), that of PRRSv was 7.5% (95% CI 2.7–14.2), that of M. hyo was 11.5% (95% CI 7.2–18.0), that of App was 25.1% (95% CI 18.5–38.0), and that of Metastrongylus spp. was 29.3% (95% CI 22.9–36.6). The odds of multiple pneumonia forms increased in pigs with multiple pathogens (ORs 2.6, p = 0.01) and Metastrongylus spp. infestation (OR 2.5, p = 0.003), suggesting synergistic effects of coinfections in the induction of lesions.

Conclusions

This study revealed a high prevalence and severity of pneumonic lesions in slaughtered pigs. It provides baseline information and evidence for the magnitude of pneumonia associated with the studied pathogens and justifies future studies on their potential economic impacts on Ugandan pigs.

Changes in the Nasal Microbiota of Pigs Following Single or Co-Infection with Porcine Reproductive and Respiratory Syndrome and Swine Influenza A Viruses

Host-microbiota interactions are important in shaping immune responses that have the potential to influence the outcome of pathogen infection. However, most studies have focused on the gut microbiota and its possible association with disease outcome, while the role of the nasal microbiota and respiratory pathogen infection has been less well studied. Here we examined changes in the composition of the nasal microbiota of pigs following experimental infection with porcine reproductive and respiratory syndrome virus 2 (PRRSV-2), swine influenza A H3N2 virus (H3N2) or both viruses. DNA extracted from nasal swabs were subjected to 16S rRNA sequencing to study the composition of the nasal microbiota. Bacterial richness fluctuated in all groups, with a slight reduction in pigs singly infected with PRRSV-2 and H3N2 during the first 5 days of infection compared to uninfected controls. In contrast, nasal bacterial richness remained relatively stable after PRRSV-2/H3N2 co-infection. PRRSV-2 and H3N2, alone or in combination differentially altered the abundance and distribution of bacterial families. Single and co-infection with PRRSV-2 or H3N2 was associated with the expansion of the Neisseriaceae family. A positive correlation between H3N2 viral load and the relative abundance of the Neisseriaceae was observed. However, further mechanistic studies are required to understand the significance of the changes in specific bacterial families following these viral infections.

Seasonal Variation in Prevalence of Mycoplasma hyopneumoniae and Other Respiratory Pathogens in Peri-Weaned, Post-Weaned, and Fattening Pigs with Clinical Signs of Respiratory Diseases in Belgian and Dutch Pig Herds, Using a Tracheobronchial Swab Sampling Technique, and Their Associations with Local Weather Conditions

Besides Mycoplasma hyopneumoniae (M. hyopneumoniae), many other viruses and bacteria can concurrently be present in pigs. These pathogens can provoke clinical signs, known as porcine respiratory disease complex (PRDC). A sampling technique on live animals, namely tracheobronchial swab (TBS) sampling, was applied to detect different PRDC pathogens in pigs using PCR. The objective was to determine prevalence of different PRDC pathogens and their variations during different seasons, including correlations with local weather conditions. A total of 974 pig farms and 22,266 pigs were sampled using TBS over a 5-year period. TBS samples were analyzed using mPCR and results were categorized and analyzed according to the season of sampling and local weather data. In samples of peri-weaned and post-weaned piglets, influenza A virus in swine (IAV-S), porcine reproductive and respiratory syndrome virus-European strain (PRRSV1), and M. hyopneumoniae were found as predominant pathogens. In fattening pigs, M. hyopneumoniae, porcine circovirus type 2 (PCV-2) and PRRSV1 were predominant pathogens. Pathogen prevalence in post-weaned and finishing pigs was highest during winter, except for IAV-S and A. pleuropneumoniae, which were more prevalent during autumn. Associations between prevalence of several PRDC pathogens, i.e., M. hyopneumoniae, PCV-2 and PRRSV, and specific weather conditions could be demonstrated. In conclusion, the present study showed that many respiratory pathogens are present during the peri-weaning, post-weaning, and fattening periods, which may complicate the clinical picture of respiratory diseases. Interactions between PRDC pathogens and local weather conditions over the 5-year study period were demonstrated.

Effectiveness of two intramuscular combined vaccines for the control of Mycoplasma hyopneumoniae and porcine circovirus type 2 in growing pigs: a randomized field trial

Background

Mycoplasma hyopneumoniae and Porcine circovirus type 2 are two economically important pathogens affecting growing pigs. Control and prevention of both diseases can be accomplished by vaccination, together with biosecurity and good management practices. Many commercial vaccines are available. The aim of this study was to assess the efficacy of Hyogen® and Circovac® administered mixed at weaning and to compare this protocol with a competitor ready-to-use (RTU) vaccine.

Case presentation

A randomised field trial was designed in a commercial farrow-to-finish farm located in France. A total of 641 pigs born from 54 different sows were included in this study. Piglets at weaning were allocated into three groups: the first one vaccinated with Hyogen® and Circovac® combined (group A), the second one vaccinated with a competitor RTU vaccine (group B) and the last one unvaccinated. Only minor local reactions for both vaccination groups could be observed which revealed a good safety of both protocols. Both vaccination schemes in this trial didn’t improve wean-to-slaughter growth performances but significantly reduced lung lesions, lung fissures and pleurisy at slaughter, produced a seroconversion for both M. hyopneumoniae and PCV-2 and significantly reduced the PCV-2 viral load in blood. When we compared groups A and B, we observed no significant differences in growth performances, mortality, clinical signs, percentages of affected lungs at slaughter, lung fissures and pleurisy, and no difference in pathogens detection. However, two statistical differences were observed between both vaccines: the mean lung lesion score and the percentage of extensive lung lesions were lower in group A. This is consistent with lower M. hyopneumoniae loads in the lower respiratory tract in pigs from group A but this difference was not statistically significant.

Conclusions

Results reported in this case study must be considered with caution since it was done in only one farm. In this trial, Hyogen® and Circovac® mixed together under field conditions offered a successful protection of growing pigs and significantly decreased the extension of lung lesions during a natural field challenge when compared with a competitor RTU vaccine.

Attenuation of Mycoplasma hyopneumoniae Strain ES-2 and Comparative Genomic Analysis of ES-2 and Its Attenuated Form ES-2L

Mycoplasma hyopneumoniae causes swine respiratory disease worldwide. Due to the difficulty of isolating and cultivating M. hyopneumoniae, very few attenuated strains have been successfully isolated, which hampers the development of attenuated vaccines. In order to produce an attenuated M. hyopneumoniae strain, we used the highly virulent M. hyopneumoniae strain ES-2, which was serially passaged in vitro 200 times to produce the attenuated strain ES-2L, and its virulence was evidenced to be low in an animal experiment. In order to elucidate the mechanisms underlying virulence attenuation, we performed whole-genome sequencing of both strains and conducted comparative genomic analyses of strain ES-2 and its attenuated form ES-2L. Strain ES-2L showed three large fragment deletion regions including a total of 18 deleted genes, compared with strain ES-2. Analysis of single-nucleotide polymorphisms (SNPs) and indels indicated that 22 dels were located in 19 predicted coding sequences. In addition to these indels, 348 single-nucleotide variations (SNVs) were identified between strains ES-2L and ES-2. These SNVs mapped to 99 genes where they appeared to induce amino acid substitutions and translation stops. The deleted genes and SNVs may be associated with decreased virulence of strain ES-2L. Our work provides a foundation for further examining virulence factors of M. hyopneumoniae and for the development of attenuated vaccines.

Anatomical Site, Typing, Virulence Gene Profiling, Antimicrobial Susceptibility and Resistance Genes of Streptococcus suis Isolates Recovered from Pigs in Spain

A set of 207 Streptococcus suis isolates were collected from ten autonomous communities from Spain in 2019 to 2020 from pigs with meningitis, pneumonic lungs, arthritic joints or other swollen viscera, to a lesser extent. Thirteen capsular types were detected being the most prevalent serotype 2 (21.7%), followed by serotypes 1 (21.3%), 9 (19.3%) and 3 (6.3%). Serotypes 2 and 9 were recovered mainly from the central nervous system (CNS), while serotype 1 was isolated mostly from swollen joints and serotype 3 from the lungs. Twenty-five isolates (12.1%) could not be typed. The most prevalent pathotype was epf + mrp + sly + luxS (49 isolates, 23.8%), and it was related mainly to serotypes 1 and 2. Serotypes 1–3 and 9 were significantly associated with anatomical sites of isolation and virulence factors, serotype 9 (CNS) and serotypes 3 and 9 (lungs) being associated with virulence profiles without the epf gene. S. suis isolates showed globally high antimicrobial resistances, but ampicillin followed by spectinomycin and tiamulin resulted in the highest activities, while the greatest resistances were detected for sulphadimethoxine, tetracyclines, neomycin, clindamycin and macrolides. A total of 87.4% isolates were positive to the tetO gene, 62.4% to the ermB gene and 25.2% to the fexA gene, while 14.6% were positive to all three genes simultaneously. A significative association between isolate resistances to tetracyclines and macrolides and the resistance genes tested was established, except for phenicol resistance and the fexA gene. A set of 14 multiresistance patterns were obtained according to the number of antimicrobials to which the isolates were resistant, the resistances to 12 or more agents being the most prevalent ones. A remarkable amount of multiresistance profiles could be seen among the S. suis serotype 9 isolates.

Estimation of the prevalence of respiratory diseases in pigs in north-eastern Poland: Survey of pulmonary lesions in pigs at a slaughterhouse

A total of 29 520 animals, from 164 batches of pigs belonging to an identical number of herds, were involved in the study. The considered population of pigs were limited to the region of north-eastern Poland involving six voivodeships. From each herd, samples of blood were collected to evaluate the antibody titres to Mycoplasma hyopneumoniae, porcine reproductive and respiratory syndrome virus, Aujeszky's disease virus and swine influenza virus. At an abattoir, the lung lesions of each batch were scored and the enzootic pneumonia-like lesion average value was calculated. Lesions, indicative of enzootic pneumonia, were found in 57.8% of the lungs. For all lungs, the enzootic pneumonia-like lesion average value was 1.74, ranging from 0.42 to 3.56 among the 164 batches. In the examined pig population, 57.8% were considered suffering from swine respiratory disease, the majority of the affected pigs came from the Podlaskie (21.7%) and Greater Poland (17.25%) voivodeships. In the most affected voivodeships, 88.37% and 85.16% of the farms were considered as disease-susceptible for Greater Poland and Podlaskie, respectively. The findings indicate that, in pigs in north-eastern Poland, the major pathogens causing pneumonia-like lesions are Mycoplasma hyopneumoniae (68.9%) and porcine reproductive and respiratory syndrome virus (44%).

Co-infection analysis of bacterial and viral respiratory pathogens from clinically healthy swine in Eastern China

Porcine respiratory disease complex (PRDC) is one of the most challenging health concerns for pig production worldwide. The aim of the present study was to determine the prevalence of pathogens associated with PRDC, including porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) and bacterial agents, such as Streptococcussuis, Haemophilus parasuis and Actinobacillus pleuropneumoniae, in clinically healthy pigs in Eastern China. Molecular detection revealed positive single‐pathogen detection rates of 59.9%, 27.2%, 52.3%, 33.2% and 0.4% for PCV2, PRRSV, S. suis, H. parasuis and A. pleuropneumoniae, respectively. Co‐infection with more than one pathogen was frequently detected in these samples, with PCV2/S. suis, H. parasuis and PCV2/H. parasuis mixed infection rates of 35.4%, 33.2% and 21.6%, respectively, and PCV2/S. suis/H. parasuis and PRRSV/PCV2/S. suis co‐infection rates of 21.6% and 6.2%, respectively. These results suggest that mixed infections are prevalent among PRDC cases in swine, which may pose a greater threat to the health of herds compared with single‐pathogen infections.

The Airway Pathobiome in Complex Respiratory Diseases: A Perspective in Domestic Animals

Respiratory infections in domestic animals are a major issue for veterinary and livestock industry. Pathogens in the respiratory tract share their habitat with a myriad of commensal microorganisms. Increasing evidence points towards a respiratory pathobiome concept, integrating the dysbiotic bacterial communities, the host and the environment in a new understanding of respiratory disease etiology. During the infection, the airway microbiota likely regulates and is regulated by pathogens through diverse mechanisms, thereby acting either as a gatekeeper that provides resistance to pathogen colonization or enhancing their prevalence and bacterial co-infectivity, which often results in disease exacerbation. Insight into the complex interplay taking place in the respiratory tract between the pathogens, microbiota, the host and its environment during infection in domestic animals is a research field in its infancy in which most studies are focused on infections from enteric pathogens and gut microbiota. However, its understanding may improve pathogen control and reduce the severity of microbial-related diseases, including those with zoonotic potential.

[The porcine respiratory disease complex (PRDC) - a clinical review]

The porcine respiratory disease complex describes a clinical condition that often manifests as treatment-resistant respiratory disease of growing to finishing pigs. Its multifactorial etiology includes infectious and non-infectious factors. Besides management and hygiene conditions, particularly viral and bacterial pathogens contribute to the development and course of PRDC. The porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), influenza A virus (IAV) and Mycoplasma (M.) hyopneunoniae are considered as the major pathogens involved in PRDC. The clinical outcome and necropsy findings may differ depending on the involvement of the different pathogens. The complex nature of the PRDC impedes the diagnostic and preventive measures on affected farms. The present review provides insight into the pathomorphology, pathogenesis and inter-pathogen-interactions and aims to support practitioners in implementing purposeful diagnostic and preventive measures.

Review of the speculative role of co-infections in Streptococcus suis-associated diseases in pigs

Streptococcus suis is one of the most important bacterial swine pathogens affecting post-weaned piglets, causing mainly meningitis, arthritis and sudden death. It not only results in severe economic losses but also raises concerns over animal welfare and antimicrobial resistance and remains an important zoonotic agent in some countries. The definition and diagnosis of S. suis-associated diseases can be complex. Should S. suis be considered a primary or secondary pathogen? The situation is further complicated when referring to respiratory disease, since the pathogen has historically been considered as a secondary pathogen within the porcine respiratory disease complex (PRDC). Is S. suis a respiratory or strictly systemic pathogen? S. suis is a normal inhabitant of the upper respiratory tract, and the presence of potentially virulent strains alone does not guarantee the appearance of clinical signs. Within this unclear context, it has been largely proposed that co-infection with some viral and bacterial pathogens can significantly influence the severity of S. suis-associated diseases and may be the key to understanding how the infection behaves in the field. In this review, we critically addressed studies reporting an epidemiological link (mixed infections or presence of more than one pathogen at the same time), as well as in vitro and in vivo studies of co-infection of S. suis with other pathogens and discussed their limitations and possibilities for improvement and proposed recommendations for future studies.