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

Gut microbiome perturbation and its correlation with tylosin pharmacokinetics in healthy and infected pigs

Tylosin, an antibiotic with a long history in treating respiratory bacterial infections, has unknown effects on the gut microbiota of healthy and infected pigs. The study aimed to investigate the effect of a therapeutic dose of tylosin on swine gut microbiota and explored the relationship between this effect and tylosin pharmacokinetics (PK). We also assessed whether changes in gut microbiota after tylosin administration differ between healthy animals (n = 7) and animals intranasally co-infected (n = 7) with Actinobacillus pleuropneumoniae and Pasteurella multocida. Both groups were intramuscularly administered with tylosin (20 mg/kg). The 16S rRNA gene analyses revealed a significantly lower species richness and diversity, after tylosin treatment, in the infected than the healthy pigs, with infected pigs having lower levels of Bacteroidetes and Firmicutes and higher levels of Proteobacteria. Greater tylosin exposure (greater area under curve (AUC) and maximum plasma concentration (Cmax), and slower elimination (longer terminal half-life, T1/2) were observed in healthy than infected pigs. Relative abundance of Lactobacillus, Oscillibacter, Prevotella, and Sporobacter was positively and significantly correlated with AUC and Cmax, whereas the abundance of Acinetobacter, Alishewanella, and Pseudomonas was positively and significantly correlated with T1/2 and mean residence time (MRT) of tylosin. Our findings, for the first time, demonstrated significant changes in swine gut microbiota after a single therapeutic dose of tylosin was administered, whereas the effect of these changes on tylosin PK was not evident.

Comparative Pharmacokinetics of Gentamicin C1, C1a and C2 in Healthy and Infected Piglets

Gentamicin, an aminoglycoside antibiotic, is a mixture of therapeutically active C1, C1a, C2 and other minor components. Despite its decades-long use in pigs and other species, its intramuscular (IM) pharmacokinetics/pharmacodynamics (PKs/PDs) are unknown in piglets. Furthermore, the PKs of many drugs differ between healthy and sick animals. Therefore, we investigated the PKs of gentamicin after a single IM dose (10 mg/kg) in healthy piglets and piglets that were intranasally co-infected with Actinobacillus pleuropneumoniae and Pasteurella multocida (PM). The plasma concentrations were measured using validated liquid chromatography/mass spectrometry. The gentamicin exposure was 36% lower based on the area under the plasma concentration-time curve and 16% lower based on the maximum plasma concentration (Cmax) in the infected piglets compared to the healthy piglets, while it was eliminated faster (shorter half-life and larger clearance) in the infected piglets compared to the healthy piglets. The clearance and volume of distribution were the highest for the C1 component. C1, C1a and C2 accounted for 22-25%, 33-37% and 40-42% of the total gentamicin exposure, respectively. The PK/PD target for the efficacy of aminoglycosides (Cmax/minimum inhibitory concentration (MIC) > 10) could be exceeded for PM, with a greater magnitude in the healthy piglets. We suggest integrating this PK information with antibiotic susceptibility data for other bacteria to make informed antibiotic and dosage regimen selections against piglet infections.

Optimizing tylosin dosage for co-infection of Actinobacillus pleuropneumoniae and Pasteurella multocida in pigs using pharmacokinetic/pharmacodynamic modeling

Formulating a therapeutic strategy that can effectively combat concurrent infections of Actinobacillus pleuropneumoniae (A. pleuropneumoniae) and Pasteurella multocida (P. multocida) can be challenging. This study aimed to 1) establish minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), time kill curve, and post-antibiotic effect (PAE) of tylosin against A. pleuropneumoniae and P. multocida pig isolates and employ the MIC data for the development of epidemiological cutoff (ECOFF) values; 2) estimate the pharmacokinetics (PKs) of tylosin following its intramuscular (IM) administration (20 mg/kg) in healthy and infected pigs; and 3) establish a PK-pharmacodynamic (PD) integrated model and predict optimal dosing regimens and PK/PD cutoff values for tylosin in healthy and infected pigs. The MIC of tylosin against both 89 and 363 isolates of A. pleuropneumoniae and P. multocida strains spread widely, ranging from 1 to 256 μg/mL and from 0.5 to 128 μg/mL, respectively. According to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) ECOFFinder analysis ECOFF value (≤64 µg/mL), 97.75% (87 strains) of the A. pleuropnumoniae isolates were wild-type, whereas with the same ECOFF value (≤64 µg/mL), 99.72% (363 strains) of the P. multicoda isolates were considered wild-type to tylosin. Area under the concentration time curve (AUC), T1/2, and Cmax values were significantly greater in healthy pigs than those in infected pigs (13.33 h × μg/mL, 1.99 h, and 5.79 μg/mL vs. 10.46 h × μg/mL, 1.83 h, and 3.59 μg/mL, respectively) (p < 0.05). In healthy pigs, AUC24 h/MIC values for the bacteriostatic activity were 0.98 and 1.10 h; for the bactericidal activity, AUC24 h/MIC values were 1.97 and 1.99 h for A. pleuropneumoniae and P. multocida, respectively. In infected pigs, AUC24 h/MIC values for the bacteriostatic activity were 1.03 and 1.12 h; for bactericidal activity, AUC24 h/MIC values were 2.54 and 2.36 h for A. pleuropneumoniae and P. multocida, respectively. Monte Carlo simulation lead to a 2 μg/mL calculated PK/PD cutoff. Managing co-infections can present challenges, as it often demands the administration of multiple antibiotics to address diverse pathogens. However, using tylosin, which effectively targets both A. pleuropneumoniae and P. multocida in pigs, may enhance the control of bacterial burden. By employing an optimized dosage of 11.94-15.37 mg/kg and 25.17-27.79 mg/kg of tylosin can result in achieving bacteriostatic and bactericidal effects in 90% of co-infected pigs.

Viral and Bacterial Profiles in Endemic Influenza A Virus Infected Swine Herds Using Nanopore Metagenomic Sequencing on Tracheobronchial Swabs

Swine influenza A virus (swIAV) plays an important role in porcine respiratory infections. In addition to its ability to cause severe disease by itself, it is important in the multietiological porcine respiratory disease complex. Still, to date, no comprehensive diagnostics with which to study polymicrobial infections in detail have been offered. Hence, veterinary practitioners rely on monospecific and costly diagnostics, such as Reverse Transcription quantitative PCR (RT-qPCR), antigen detection, and serology. This prevents the proper understanding of the entire disease context, thereby hampering effective preventive and therapeutic actions. A new, nanopore-based, metagenomic diagnostic platform was applied to study viral and bacterial profiles across 4 age groups on 25 endemic swIAV-infected German farms with respiratory distress in the nursery. Farms were screened for swIAV using RT-qPCR on nasal and tracheobronchial swabs (TBS). TBS samples were pooled per age, prior to metagenomic characterization. The resulting data showed a correlation between the swIAV loads and the normalized reads, supporting a (semi-)quantitative interpretation of the metagenomic data. Interestingly, an in-depth characterization using beta diversity and PERMANOVA analyses allowed for the observation of an age-dependent interplay of known microbial agents. Also, lesser-known microbes, such as porcine polyoma, parainfluenza, and hemagglutinating encephalomyelitis viruses, were observed. Analyses of swIAV incidence and clinical signs showed differing microbial communities, highlighting age-specific observations of various microbes in porcine respiratory disease. In conclusion, nanopore metagenomics were shown to enable a panoramic view on viral and bacterial profiles as well as putative pathogen dynamics in endemic swIAV-infected herds. The results also highlighted the need for better insights into lesser studied agents that are potentially associated with porcine respiratory disease. IMPORTANCE To date, no comprehensive diagnostics for the study of polymicrobial infections that are associated with porcine respiratory disease have been offered. This precludes the proper understanding of the entire disease landscape, thereby hampering effective preventive and therapeutic actions. Compared to the often-costly diagnostic procedures that are applied for the diagnostics of porcine respiratory disease nowadays, a third-generation nanopore sequencing diagnostics workflow presents a cost-efficient and informative tool. This approach offers a panoramic view of microbial agents and contributes to the in-depth observation and characterization of viral and bacterial profiles within the respiratory disease context. While these data allow for the study of age-associated, swIAV-associated, and clinical symptom-associated observations, it also suggests that more effort should be put toward the investigation of coinfections and lesser-known pathogens (e.g., PHEV and PPIV), along with their potential roles in porcine respiratory disease. Overall, this approach will allow veterinary practitioners to tailor treatment and/or management changes on farms in a quicker, more complete, and cost-efficient way.

Metagenomic Approach Reveals the Second Subtype of PRRSV-1 in a Pathogen Spectrum during a Clinical Outbreak with High Mortality in Western Siberia, Russia

Porcine reproductive and respiratory syndrome virus (PRRSV) has a significant economic impact on pig farming worldwide by causing reproductive problems and affecting the respiratory systems of swine. In Eastern Europe, PRRSV-1 strains are characterized by high genetic variability, and pathogenicity differs among all known subtypes. This case study describes the detection of a wide pathogen spectrum, including the second subtype PRRSV-1, with a high mortality rate among nursery piglets (23.8%). This study was conducted at a farrow-to-finish farm in the Western Siberia region of Russia. Clinical symptoms included apathy, sneezing, and an elevation in body temperature, and during the autopsy, degenerative lesions in different tissues were observed. Moreover, 1.5 percent of the affected animals displayed clinical signs of the central nervous system and were characterized by polyserositis. Nasal swabs from diseased piglets and various tissue swabs from deceased animals were studied. For diagnostics, the nanopore sequencing method was applied. All the samples tested positive for PRRSV, and a more detailed analysis defined it as a second subtype of PRRSV-1. The results, along with the clinical picture, showed a complex disease etiology with the dominant role of PRRSV-1 and were informative about the high pathogenicity of the subtype in question under field conditions.

Clinical Efficacy of Two Novel, Differentially Administered (IM, ID) Vaccines against Mycoplasma hyopneumoniae and PCV2 in Swine under Field Conditions

Enzootic pneumonia (EP) of pigs is caused by Mycoplasma hyopneumoniae (M.hp.), which is, together with the porcine circovirus type 2 (PCV2), among the most prominent inducers of the porcine respiratory disease complex (PRDC). Therefore, vaccination of piglets against M.hp. and PCV2 is crucial in the fight against pulmonary infections. In this field study, we tested the clinical efficacy of two novel vaccines, one delivered IM (Hyogen^® + Circovac^®) and the other ID (MHyo-Sphere^®PCV ID), on a fattening farm in Lower Austria with a history of still ongoing EP. Average daily weight gain, coughing/sneezing index, losses due to morbidity/mortality, and lung scoring data at slaughter by means of CLP (Ceva Lung Program) were recorded for three consecutive fattening cohorts to achieve a powerful number of animals, one half each vaccinated with the IM vaccine and the other half with the ID vaccine (n = 659 in total). No statistically significant differences could be observed between the two vaccination groups for the parameters investigated, but the total median EP score, which categorizes pulmonary lesions due to infection by M.hp. with a theoretical range of 0-28, was lowered from initially 1.9 to 1.0, indicating that both vaccines proved very suitable measures in the fight against EP.

Mycoplasma hyopneumoniae Infection Activates the NOD1 Signaling Pathway to Modulate Inflammation

Mycoplasma hyopneumoniae is a highly contagious pathogen causing porcine enzootic pneumonia, which elicits prolonged inflammatory response modulated by pattern recognition receptors (PRRs). Although significant advances have been achieved in understanding the Toll-Like receptors that recognize M. hyopneumoniae, the role of nucleotide-binding oligomerization domain 1 (NOD1) in M. hyopneumoniae infected cells remains poorly understood. This study revealed that M. hyopneumoniae activates the NOD1-RIP2 pathway and is co-localized with host NOD1 during infection. siRNA knockdown of NOD1 significantly impaired the TRIF and MYD88 pathway and blocked the activation of TNF-α. In contrast, NOD1 overexpression significantly suppressed M. hyopneumoniae proliferation. Furthermore, we for the first time investigated the interaction between M. hyopneumoniae mhp390 and NOD1 receptor, and the results suggested that mhp390 and NOD1 are possibly involved in the recognition of M. hyopneumoniae. These findings may improve our understanding of the interaction between PRRs and M. hyopneumoniae and the function of NOD1 in host defense against M. hyopneumoniae infection.

Genetic Diversity and Epidemic Types of Porcine Reproductive and Respiratory Syndrome (PRRS) Virus in Japan from 2018 to 2020

To clarify the genetic diversity of the porcine reproductive and respiratory syndrome virus (PRRSV) in Japan in recent years, we determined the nucleotide sequence of open reading frame 5 of 2482 PRRSV sequences obtained from samples collected from pigs between January 2018 and December 2020. As a result of molecular phylogenetic analysis, Cluster II represented the largest proportion (44.9−50.6%) throughout the study period, followed by Cluster IV (34.0−40.8%), Cluster III (7.8−12.1%), Cluster I (3.1−6.7%), and Cluster V (0.1−0.2%). The relative distributions between Clusters varied between geographic regions and between years: in 2018, Cluster II was the most prevalent in all regions. In 2019, Cluster II was dominant in the Hokkaido and Tohoku regions, while in other regions Cluster IV was dominant. In 2020, Cluster IV was dominant in the Kanto/Tosan and Kyushu/Okinawa regions, whilst in other regions Cluster II was predominant. Compared with a previous study, the proportions of genome sequences classified in Clusters II and IV significantly increased (p = 0.042 and 0.018, respectively) and those classified in Cluster III significantly decreased (p < 0.01). The widespread use of live attenuated vaccines using strains that belong to Cluster II might have accounted for these changes in the relative distribution between Clusters.

[Performance parameters and pathogen detection in pig groups differently vaccinated with respect to Porcine Circovirus Type 2 and Mycoplasma hyopneumoniae]

OBJECTIVE

Respiratory diseases, mostly multifactorial, cause problems in pig farms worldwide. Next to infectious agents, such as Porcine Circovirus Type 2 (PCV2) and Mycoplasma hyopneumoniae (M. hyopneumoniae) management, housing, and environmental factors are decisive for the development of disease. In a conventional, closed swine farm in Lower Saxony, Germany, which did not vaccinate against PCV2, the effect of an implementation of PCV2 vaccination (Suvaxyn^® Circo + MH RTU) onto animal health was evaluated. In addition, the effect of this combination vaccine was assessed in comparison to simultaneous administration of mono-vaccines against PCV2 and M. hyopneumoniae. MATERIAL AND METHOD: In a two-phase trial, 524 (phase 1) or 521 (phase 2) clinically healthy piglets were included at the first week of life. In the first phase, performance parameters were compared in animals vaccinated against M. hyopneumoniae only (group A) or vaccinated against PCV2 and M. hyopneumoniae (group B). In phase 2, vaccination against PCV2 and M. hyopneumoniae with different vaccines were compared (groups C and D). Performance parameters included lifetime animal losses, daily weight gains during suckling, weaning and fattening, and randomly sampled pathogen loads in serum (PCV2) or tracheobronchial secretions (M. hyopneumoniae). In addition, an assessment of the lungs was performed after slaughter.

RESULTS

In the first phase, it was shown that the group vaccinated against PCV2 (Group B: Suvaxyn^® Circo + MH RTU) had higher daily growth rates during the fattening period (+ 37 g, p = 0.012) as well as during the complete period (+ 16 g, p = 0.013) in comparison to the group without PCV2 vaccination (Group A). In group A a significantly higher proportion of animals showed a PCV2 viremia. In the second phase, it was shown that group D was not inferior to the established vaccination regiment of group C. In fattening pigs in week 22 of life, detection rates for M. hyopneumoniae in tracheobronchial secretions were in the range of 27-80 % irrespective of the vaccination group.

CONCLUSION

Vaccination against PCV2 leads to improved animal health and higher daily weight gains.

CLINICAL RELEVANCE

The combined vaccine studied here provides farmers and veterinarians with an additional option for the improvement of animal health in pig production.