Impact of diversity of Mycoplasma hyopneumoniae strains on lung lesions in slaughter pigs.

The importance of diversity of Mycoplasma hyopneumoniae (M. hyopneumoniae) strains is not yet fully known. This study investigated the genetic diversity of M. hyopneumoniae strains in ten pig herds, and assessed associations between the presence of different strains of M. hyopneumoniae and lung lesions at slaughter. Within each herd, three batches of slaughter pigs were investigated. At slaughter, from each batch, 20 post mortem bronchoalveolar lavage fluid samples were collected for multiple locus variable-number tandem repeat analysis (MLVA), and lung lesions (Mycoplasma-like lesions, fissures) were examined. Multivariable analyses including potential risk factors for respiratory disease were performed to assess associations between the number of different strains per batch (three categories: one strain, two-six strains, ≥seven strains), and the lung lesions as outcome variables. In total, 135 different M. hyopneumoniae strains were found. The mean (min.-max.) number of different strains per batch were 7 (1-13). Batches with two-six strains or more than six strains had more severe Mycoplasma-like lesions (P = 0.064 and P = 0.012, respectively), a higher prevalence of pneumonia [odds ratio (OR): 1.30, P = 0.33 and OR: 2.08, P = 0.012, respectively], and fissures (OR = 1.35, P = 0.094 and OR = 1.70, P = 0.007, respectively) compared to batches with only one strain. In conclusion, many different M. hyopneumoniae strains were found, and batches of slaughter pigs with different M. hyopneumoniae strains had a higher prevalence and severity of Mycoplasma-like lung lesions at slaughter, implying that reducing the number of different strains may lead to less lung lesions at slaughter and better respiratory health of the pigs.

Effect of sow vaccination against porcine circovirus type 2 (PCV2) on virological profiles in herds with or without PCV2 systemic disease.

We investigated porcine circovirus type 2 (PCV2) virological profiles in herds affected (PCVAD-AH, n = 5) or non-affected (PCVAD-NAH, n = 4) by PCV2-associated diseases (PCVAD), before and after 1 y of PCV2 gilt and sow vaccination. Fresh feces from the floor (5 pens/age/farm) and 5 blood samples (1/pen) were collected at 3, 9, 15, 21 wk. Individual feces and blood samples were collected from 5 gilts and 15 sows. Sampling was repeated 1 y after vaccination. Quantitative PCR on feces, PCV2 antibodies in blood serum and cell-mediated immunity were investigated. Before vaccination, pigs of PCVAD-AH had higher viral load in feces (9 and 15 wk), lower IgG and higher IgM (3 wk) and lower lymphocyte counts (9 and 15 wk) suggesting immunosuppression. Vaccination reduced viral load in growers, increased IgG (3 wk) suggesting improved maternal immunity, reduced IgM (3 wk), increased total antibody titers in sows and increased CD79a cells in the pigs.

Effet de la vaccination des truies contre le circovirus porcin de type 2 (PCV2) sur les profils virologiques des troupeaux atteints ou non de la maladie systémique PCV2. Nous avons fait une enquête sur les profils virologiques du circovirus porcin de type 2 (PCV2) dans les troupeaux affectés (PCVAD-AH, n = 5) ou non affectés (PCVAD-NAH, n = 4) par les maladies associées au PCV2 (MAPCV), 1 an avant et 1 an après la vaccination des cochettes et des truies contre le PCV2. Des fèces fraîches sur le plancher (5 enclos/âge/ferme) et 5 échantillons de sang (1/enclos) ont été prélevés à 3, 9, 15 et 21 semaines. Des fèces individuelles et des échantillons sanguins ont été préIevés auprès de 5 cochettes et de 15 truies. L'échantillonnage a été répété 1 an après la vaccination. La RCP quantitative sur les fèces, les anticorps de PCV2 dans le sérum sanguin et l'immunité à médiation cellulaire ont fait l'objet d'une enquête. Avant la vaccination, les porcs de PCVAD-AH présentaient une charge virale supérieure dans les fèces (à 9 et à 15 semaines), une IgG inférieure et une IgM supérieure (à 3 semaines) ainsi qu'une numération inférieure des lymphocytes (à 9 et à 15 semaines) suggérant l'immunosuppression. La vaccination a réduit la charge virale chez les porcs en croissance, a augmenté les IgG (à 3 semaines) suggérant une immunité maternelle améliorée, a réduit les IgM (à 3 semaines), a augmenté le total des titres d'anticorps chez les truies et a augmenté les cellules CD79a chez les porcs.(Traduit par Isabelle Vallières).

Efficacy of Mycoplasma hyopneumoniae vaccination before and at weaning against experimental challenge infection in pigs.

BACKGROUND: Commercial bacterins are widely used at weaning to control Mycoplasma hyopneumoniae infections in pigs. However, it is not known whether the efficacy of vaccinating against M. hyopneumoniae can be influenced by the weaning process when vaccination is applied at the day of weaning. The present study assessed the efficacy of a single M. hyopneumoniae vaccination (Ingelvac MycoFLEX®) three days before weaning (V1) or at weaning (V2) against experimental challenge infection. Four weeks after vaccination, groups V1 and V2 (n = 20 pigs each) and a non-vaccinated, positive control group (PCG) (n = 20) were endotracheally inoculated with a virulent M. hyopneumoniae field strain. Five pigs were used as a negative control group. All pigs were euthanized 5 weeks after challenge. The main parameters investigated included macroscopic and histopathological lung lesions at necropsy, immunofluorescence (IF) staining and quantitative real-time PCR (qPCR) on broncho-alveolar lavage (BAL) fluid for quantifying M. hyopneumoniae. RESULTS: The average macroscopic lung lesion scores in groups V1, V2 and PCG were 0.54, 0.88 and 1.04, respectively (P > 0.05). The average lymphohistiocytic infiltration scores in groups V1, V2 and PCG were 2.95, 3.16 and 3.61, respectively (P < 0.05). The average IF scores were: V1 = 1.13, V2 = 1.19 and PCG = 1.25 (P > 0.05), the qPCR values were: V1 = 10(2.94), V2 = 10(2.76) and PCG = 10(3.23) (P > 0.05). All pigs of the negative control group remained negative throughout the study. CONCLUSIONS: Both vaccinated groups had lower numbers of macroscopic and histopathological lung lesions, and lower numbers of M. hyopneumoniae organisms in the BAL fluid compared to the PCG. However, no firm conclusions could be made on whether weaning negatively influences the efficacy of M. hyopneumoniae vaccination, since significant differences between the treatment groups were only obtained for the histopathological lung lesions. This could be attributed to the fact that milder macroscopic lung lesions were produced in the inoculated pigs, when compared to previous trials conducted by the same group. Further research under field conditions is warranted to assess possible differences between the two vaccination strategies.

Local and systemic immune responses in pigs intramuscularly injected with an inactivated Mycoplasma hyopneumoniae vaccine.

The immune response induced by intramuscular administration of a commercial inactivated Mycoplasma hyopneumonie whole-cell vaccine (Suvaxyn(®)MH One) was investigated in conventional M. hyopneumoniae-free pigs. The animals were assigned randomly to two groups: non-vaccinated and vaccinated. Pigs in the vaccinated group were injected intramuscularly with the vaccine at 7 days of age, whereas non-vaccinated pigs received physiological saline solution (PBS). Pigs were euthanized and necropsied at 30, 36 and 58 days of age. Blood, bronchoalveolar lavage (BAL) fluid, spleen, lung and bronchial lymph nodes (BLN) were collected. Serum and BAL fluid were tested for the presence of antibodies by ELISA. Monomorphonuclear cells from the peripheral blood and tissues were isolated to quantify the T cell subsets by flow cytometry, and cytokine production by ELIspot and ELISA. Antibodies against M. hyopneumoniae were detected in serum of most vaccinated pigs at 30 days of age. M. hyopneumoniae specific IgG, IgM and IgA were detected in BAL fluid from vaccinated animals, but not from control animals. Significantly higher numbers of IL-12 secreting cells were observed in the lung at day 58 in the vaccinated than in the non-vaccinated group (p<0.05). The number of IL-10 secreting cells from BLN was also higher in the vaccinated group at day 58 (p<0.05). After restimulation in vitro, lymphocytes from BLN and lungs secreted significantly higher levels of IL-12 in the vaccinated group at day 58. These results show that the vaccine induced both systemic and mucosal cellular and humoral immune responses.