Detection of Mycoplasma hyopneumoniae in piglet processing fluids

Concentrations of selected immunological parameters in the serum and processing fluid of suckling piglets and the serum and colostrum of their mothers

BACKGROUND

Blood sampling from neonatal piglets is related to multiple disadvantages. Therefore, a new, alternative matrix is required to assess piglets' early immune status efficiently. The present study aimed to assess the usefulness of processing fluid for determining selected piglets' immune parameters. 264 pigs - 31 sows, 146 male piglets, and 87 female piglets from commercial indoor farrow-to-finish pig herd were included in this study. 264 serum, 31 colostrum, and 146 processing fluid samples were collected. Serum was collected from all animals, colostrum was collected from sows, and processing fluid was collected from male piglets only. Using commercial ELISA tests, the concentration of various immunoglobulins, cytokines, and acute phase proteins was assessed in each matrix. Statistical analyses were employed to determine differences in the concentration of measured indices between piglets' serum and processing fluid and correlations in the concentration of tested indices between particular sets of matrices.

RESULTS

Statistical analyses did not reveal significant differences in the IgG, IgA, IL-1β, IL-4, IL-6, and IFN-γ concentration between piglets' serum and processing fluid (p > 0.05). A positive correlation (p < 0.05) regarding the concentration of some indices between processing fluid and samples collected from sows was also observed.

CONCLUSIONS

Processing fluid can be considered a promising alternative to blood for assessing some immunological indices in piglets, such as IgG, IgA, IL-1β, IL-4, IL-6, and IFN-γ, and, possibly, in the indirect assessment of some indices in lactating sows, including IgA, IL-1β, IL-4, IL-6, IL-8, IFN-γ, or Pig-MAP.

Considerations in the use of processing fluids for the detection of PRRSV RNA and antibody

Surveillance is mandatory for tracking the progress of porcine reproductive and respiratory syndrome virus (PRRSV) control and elimination efforts in breeding herds. Processing fluids, the fluid recovered from tissues collected at castration and/or tail docking, are used for breeding herd surveillance by large segments of the industry, but the basic diagnostic characteristics of processing fluids are largely undescribed. We undertook 3 studies to address this information gap. In study 1, we found no differences among the PRRSV RT-rtPCR results obtained with 4 commercial RNA extraction kits. In study 2, we found that PRRSV RNA was highly stable in processing fluid samples at -20°C or 4°C, but detrimental effects were observed at ≥22°C within 24 h. In study 3, using a modified PRRSV ELISA at a sample:positive cutoff of ≥0.5, we found excellent discrimination in the detection of PRRSV antibody (IgM, IgA, IgG) in processing fluids from herds of known PRRSV status. Judicious handling of processing fluid samples from sow herds, and the use of methods available in veterinary diagnostic laboratories, can provide a foundation for reliable PRRSV surveillance.

Improving Mycoplasma hyopneumoniae diagnostic capabilities by harnessing the infection dynamics

Mycoplasma hyopneumoniae remains one of the most problematic bacterial pathogens for pig production. Despite an abundance of observational and laboratory testing capabilities for this organism, diagnostic interpretation of test results can be challenging and ambiguous. This is partly explained by the chronic nature of M. hyopneumoniae infection and its tropism for lower respiratory tract epithelium, which affects diagnostic sensitivities associated with sampling location and stage of infection. A thorough knowledge of the available tools for routine M. hyopneumoniae diagnostic testing, together with a detailed understanding of infection dynamics, are essential for optimizing sampling strategies and providing confidence in the diagnostic process. This study reviewed known information on sampling and diagnostic tools for M. hyopneumoniae and summarized literature reports of the dynamics of key infection outcomes, including clinical signs, lung lesions, pathogen detection, and humoral immune responses. Such knowledge could facilitate better understanding of the performance of different diagnostic approaches at various stages of infection.

High Prevalence of Porcine Circovirus 3 in Hungarian Pig Herds: Results of a Systematic Sampling Protocol

Porcine circovirus type 3 (PCV3) is an emerging pathogen that has been reported worldwide in all ages of healthy and clinically ill pigs. The presence of this virus in Hungary has been confirmed in a commercial farm experiencing reproductive failures, but there were no data on the circulation of PCV3 in the country. Here we report the prevalence and the genetic diversity of PCV3 in Hungarian herds. To estimate the prevalence, 1855 serum samples, 176 oral fluid and 97 processing fluid samples were collected in a systematic, cross-sectional method from 20 large scale swineherds and tested by real-time qPCR. PCV3 was present in at least one type of diagnostic matrix in 19 out of the 20 (95%) pig farms. The highest detection rates were observed in the processing fluid samples (61%), but 41% of the oral fluid and 23% of the serum samples were positive. The virus was found in all age groups, and slightly more adult animals were infected than growing pigs, but the viral burden was lower amongst them. Phylogenetic analysis of nine complete genomes, obtained from either the sampled herds or organ samples of PCV3-positive carcasses, showed high nucleotide identity between the detected sequences, which all belonged to the PCV3a genotype. Our results indicate that PCV3 is widespread in Hungary, but in most cases, the virus seems to circulate subclinically, infecting all age groups and production phases without the presence of apparent clinical disease.

Genomic Variability and Post-translational Protein Processing Enhance the Immune Evasion of Mycoplasma hyopneumoniae and Its Interaction With the Porcine Immune System

Mycoplasma hyopneumoniae (M. hyopneumoniae, Mhp) is a geographically widespread and economically devastating pathogen that colonizes ciliated epithelium; the infection of Mhp can damnify the mucociliary functions as well as leading to Mycoplasma pneumonia of swine (MPS). MPS is a chronic respiratory infectious disease with high infectivity, and the mortality can be increased by secondary infections as the host immunity gets down-regulated during Mhp infection. The host immune responses are regarded as the main driving force for the disease development, while MPS is prone to attack repeatedly in farms even with vaccination or other treatments. As one of the smallest microorganisms with limited genome scale and metabolic pathways, Mhp can use several mechanisms to achieve immune evasion effect and derive enough nutrients from its host, indicating that there is a strong interaction between Mhp and porcine organism. In this review, we summarized the immune evasion mechanisms from genomic variability and post-translational protein processing. Besides, Mhp can induce the immune cells apoptosis by reactive oxygen species production, excessive nitric oxide (NO) release and caspase activation, and stimulate the release of cytokines to regulate inflammation. This article seeks to provide some new points to reveal the complicated interaction between the pathogen and host immune system with Mhp as a typical example, further providing some new strategies for the vaccine development against Mhp infection.

Paracellular Pathway-Mediated Mycoplasma hyopneumoniae Migration across Porcine Airway Epithelial Barrier under Air-Liquid Interface Conditions

Mycoplasma hyopneumoniae is an important respiratory pathogen of pigs that causes persistent and secondary infections. However, the mechanisms by which this occurs are unclear. In this study, we established air-liquid interface culture systems for pig bronchial epithelial cells (ALI-PBECs) that were comparable to the conditions in the native bronchus in vivo We used this ALI-PBECs model to study the infection and migration characteristics of M. hyopneumoniae in vitro Based on the results, we confirmed that M. hyopneumoniae was able to adhere to ALI-PBECs and disrupt mucociliary function. Importantly, M. hyopneumoniae could migrate to the basolateral chamber through the paracellular route but not the transcellular pathway, and this was achieved by reversibly disrupting tight junctions (TJs) and increasing the permeability and damaging the integrity of the epithelial barrier. We examined the migration ability of M. hyopneumoniae using an ALI-PBECs model for the first time. The disruption of the epithelial barrier allowed M. hyopneumoniae to migrate to the basolateral chamber through the paracellular route, which may be related to immune evasion, extrapulmonary dissemination, and persistent infection of M. hyopneumoniae.