Exploratory field study on the effect of Porcine circovirus 2 (PCV2) sow vaccination on serological, virological and reproductive parameters in a PCV2 subclinically infected sow herd.

BACKGROUND: This study sought to evaluate the effect of sow vaccination against Porcine circovirus 2 (PCV2) on reproductive parameters during two consecutive reproductive cycles. The study was performed in a PCV2 subclinical infected breeding herd (PCV2 circulation but absence of major reproductive problems). Ninety-four pregnant sows were primo-immunized with a commercial PCV2 vaccine and ninety-seven were injected with phosphate-buffered saline at 6 and 3 weeks before the first studied farrowing, and then boosted at 2 weeks before the second one. Blood samples were taken throughout the study to assess PCV2 DNA load and antibodies. At farrowing, main reproductive parameters and piglet vitality index were registered. In addition, in those litters with more than three mummified or stillborn piglets, microscopic examination and PCV2 antigen detection in foetal myocardium was done. RESULTS: Vaccinated sows showed significantly higher antibody levels compared to the non-vaccinated counterparts. PCV2 DNA was only detected at farrowing in 2 (4.2%) non-vaccinated sows. Vaccinated sows had 1.3 more live-born piglets per litter at the second cycle than non-vaccinated counterparts. Piglets from vaccinated sows had significantly higher (+ 12.7%) vitality score than the ones born from non-vaccinated sows. No PCV2 compatible lesions neither PCV2 antigen were detected in the tested foetal hearts. CONCLUSIONS: The present study represents a first attempt to demonstrate that PCV2 sow vaccination may have a positive influence on prolificacy and vitality of the offspring in a subclinical infected breeding herd. However, since reproductive outcomes at farm level may be affected by a number of factors, further studies would be needed to confirm this association.

Evaluation of natural porcine circovirus type 2 (PCV2) subclinical infection and seroconversion dynamics in piglets vaccinated at different ages.

This study aimed to determine the porcine circovirus type 2 (PCV2) serological and virological dynamics in piglets vaccinated at different ages in a PCV2 subclinical infection (PCV2-SI) scenario. Six hundred and forty-four 2 week-old healthy piglets were selected and distributed into four treatment groups: vaccination at 3, 6 or 10 weeks of age (3W-VAC, 6W-VAC and 10W-VAC groups, respectively) and unvaccinated pigs (NON-VAC group). Blood (n = 112 pigs) and oral fluid (OF) (n = 40 pens) samples were taken throughout the study to assess PCV2 load, humoral immunity and viral genotyping. Percentage of PCV2-DNA positive sera mainly raised by 10 weeks of age, being maximum at 14 weeks of age, and then started to decrease at 18 and 25 weeks of age. Specifically, PCV2 vaccination at 3 or 6 weeks of age yielded similar results, since they produced an earlier seroconversion and reduced, at different sampling points, the proportion of viremic animals in comparison to the unvaccinated group. In contrast, PCV2 vaccination at 10 weeks of age only achieved such reduction at 25 weeks of age; in this case, vaccination coincided with the increase of the percentage of viremic pigs in the population. Both serological techniques used in sera and OF offered similar results with a high and statistically significant correlation. In contrast, a higher percentage of PCV2 DNA positivity was detected in OF in comparison with sera. In conclusion, under the present study conditions, the optimal time for PCV2 piglet vaccination was at either 3 or 6 weeks of age.

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).

Interleukin-4, interleukin-5, and interleukin-13 gene expression in cultured mononuclear cells from porcine circovirus type 2-vaccinated pigs after cells were challenged with porcine circovirus type 2 open reading frame 2 antigen.

OBJECTIVE: To characterize the kinetics of interleukin (IL)-4, IL-5, and IL-13 secretion in peripheral blood and lymph node mononuclear cells isolated from porcine circovirus type 2 (PCV2)-vaccinated pigs after cells were challenged with PCV2 open reading frame 2 antigen. ANIMALS: 10 pigs. PROCEDURES: 5 pigs were vaccinated with a PCV2 vaccine and received a booster dose 3 weeks later. They were kept together with a similar group of 5 nonvaccinated pigs that served as controls. One week after the second vaccination, peripheral blood mononuclear cells (PBMCs) and excised retropharyngeal lymph node mononuclear cells (LNMCs) were isolated and cultured. Cells were then challenged by exposure to PCV2 open reading frame 2 and evaluated at 2, 12, 24, and 48 hours to determine the expression of IL-4, IL-5, and IL-13 via quantitative PCR assay. Changes in gene expression were analyzed relative to the results from analysis of the sample at 0 hours (calibrator). RESULTS: All ILs were upregulated differently in LNMCs and PBMCs from vaccinated pigs. Lymph node mononuclear cells from vaccinated animals produced significantly more IL-4 mRNA than did PBMCs at 2, 12, and 48 hours (relative change: 2.8 vs -3.6, 13.0 vs 3.6, and 9.8 vs 1.8, respectively) and more IL-5 mRNA at 2, 12, 24, and 48 hours (relative change: 1. 2 vs -4.8, 2.2 vs 0.2, 3.2 vs -1.9, and 4.0 vs -3.6, respectively). Interleukin-13 mRNA reached its highest concentration at 24 hours but was 11.9-fold higher in PBMCs than in LNMCs. CONCLUSIONS AND CLINICAL RELEVANCE: Results supported the importance of IL-4, IL-5, and IL-13 in pigs, suggesting that PBMCs and LNMCs express cytokines in a tissue-specific manner.

Reproduction in porcine circovirus type 2 (PCV2) seropositive gilts inseminated with PCV2b spiked semen.

BACKGROUND: Since 1999, field evidence of transplacental infection by porcine circovirus type 2 (PCV2) and reproductive failure has been reported in pigs. The objective of this study was to evaluate the clinical and pathological consequences of PCV2 infection in conventional PCV2-seropositive gilts by insemination with PCV2b-spiked semen. RESULTS: Six PCV2 seropositive gilts were inseminated with PCV2b-supplemented semen (infected) and three animals with semen and cell culture medium (controls). Only three out of the six infected animals were pregnant by ultrasonography on day 29 after insemination, while two out of the three controls were pregnant. One control gilt aborted on day 23 after insemination but not due to PVC2. Viraemia was demonstrated in four out of six infected and in one control gilt that became infected with PCV2a. Anti-PCV2 antibody titres showed dynamic variations in the infected group throughout the study. Among infected gilts, the animal with the lowest anti-PCV2 titre (1/100) at the beginning of the experiment and another that reached a similar low value during the experiment showed evident seroconversion over time and had also PCV2 positive foetuses. One placenta displayed mild focal necrosis of the chorionic epithelium positively stained by immunohistochemistry for PCV2 antigen. CONCLUSIONS: PCV2-seropositive gilts can be infected with PCV2 after intrauterine exposure and low maternal antibody titre may increase the probability of a foetal infection.