Descriptive analyses of maternally-derived antibody levels against porcine circovirus 2 (PCV-2) in 3- and 21-day-old piglets from farms of four European countries using different vaccination protocols in sows.

BACKGROUND: Up to now, information on the levels of maternally-derived antibodies (MDA) against PCV-2 in suckling piglets born to sows vaccinated with different strategies is scarce in the literature. In the present observational study, the PCV-2-specific MDA titres from piglets from 109 farms (thirty 3-day-old and thirty 21-day-old piglets per farm) across four different European countries (France n = 30, Germany n = 27, Italy n = 22 and Spain n = 30) using different sow vaccination strategies (during gestation, as a gilt, as a piglet or never) were assessed. RESULTS: In all four countries, mean log PCV-2 MDA titres were higher in 3-day-old piglets than in the 3-week-old ones, being significant in most of all the comparisons performed. Within each country, the highest PCV-2-specific MDA titres were observed in the 3-day-old piglets born to sows vaccinated during gestation. Indeed, in the four countries, more than 60% of this subpopulation (3-day-old piglets from sows vaccinated during pregnancy) had the highest log PCV-2 titres detectable with the ELISA technique used in this study. The lowest MDA titres were more variable. Whereas in France and Germany the lowest titres corresponded to 21-day-old piglets born from sows vaccinated as a piglet, in Italy, they corresponded to 21-day-old piglets derived from sows vaccinated as a gilt and in Spain to 21-day-old piglets born from non-vaccinated sows. In this study, PCV-2-specific MDA titres at 3 and 21 days of age were not affected by sow parity. CONCLUSIONS: Data obtained could be considered as a European global overview of PCV-2-specific MDA titres present in the pre-vaccinated piglet populations in different European countries, with titres tending to be higher in younger piglets, but with values variable among countries and sow vaccination strategies.

Comparison of Mycoplasma hyopneumoniae and porcine circovirus 2 commercial vaccines efficacy when applied separate or combined under experimental conditions.

BACKGROUND: Mycoplasma hyopneumoniae (Mhyo) and Porcine circovirus 2 (PCV-2) are two of the most significant infectious agents causing economic losses in the weaning to slaughter period. Due to their similar vaccination age, the objective of this study was to assess the efficacy of two already existing Mhyo (Hyogen®) and PCV-2 (Circovac®) vaccines when administered separately or combined (RTM) by means of Mhyo or PCV-2 experimental challenges. RESULTS: Seven groups of animals were included in the study, being three of them challenged with PCV-2, three with Mhyo and one composed of non-challenged, non-vaccinated pigs. Within each experimental challenge, non-vaccinated (NV) groups were compared with double vaccinated groups using the commercial products separated (VS) or combined (VC). Both vaccinated groups showed significant differences for most parameters measured regarding PCV-2 (serology, percentage of infected animals and viral load in tissues) and Mhyo (serology and gross lesions) when compared to NV groups. VS and VC offered similar results, being only significantly different the PCV-2 antibody values at different time points (higher in the VS group) of the study, although not at the termination day (21 days post-PCV-2 inoculation). CONCLUSION: The present study expands the knowledge on the possibility of using two separate Mhyo and PCV-2 commercial vaccines as a RTM product, which offered equivalent virological, immunological and pathological outcomes as compared to these vaccines when used by separate.

UV-C irradiation is able to inactivate pathogens found in commercially collected porcine plasma as demonstrated by swine bioassay.

Liquid porcine plasma is an animal origin raw material for the manufacturing process of spray-dried porcine plasma that is used in pig nutrition worldwide. In previous studies we found that the application of ultraviolet light C (UV-C) in liquid plasma that was inoculated with a variety of bacteria or viruses of importance in the swine industry can be considered as redundant safety steps because in general achieve around 4 logs reduction for most of these pathogens. However, the final validation of the UV-C light as safety feature should be conducted with commercial liquid plasma and using the pig bioassay model. As a first objective, the potential infectivity of a raw liquid plasma product collected from an abattoir was tested by means of a swine bioassay. We used Porcine circovirus 2 (PCV-2), a ubiquitous virus that has been systematically detected by PCR in porcine plasma at abattoirs as selection criteria for commercial liquid plasma lot. As a second aim of the study, the effects of different doses of UV-C irradiation on the selected raw liquid plasma were assayed in the animal bioassay. Moreover, other swine infecting agents, including Porcine reproductive and respiratory syndrome virus (PRRSV), were also determined in the original plasma and monitored in the inoculated animals. Pigs negative for PCV-2 and PRRSV genome and antibodies were allotted to one of five groups (6 to 8 pigs/ group) and injected intra-peritoneally with 10 mL of their assigned inoculum at 50 d of age. Negative control pigs (group 1) were injected with PBS. Positive control pigs (group 5) were injected with a PCV-2 inoculum. Groups 2, 3 and 4 were injected with liquid porcine plasma that had been subjected to 0 (raw plasma), 3000 or 9000 J/L UV-C irradiation, respectively. Group 2 pigs (0 J/L UV-C) got infection by PRRSV but no PCV-2 infection or seroconversion. However, one pig from group 2 seroconverted to Rotavirus A (RVA) and Hepatitis E virus (HEV) and three group 2 pigs seroconverted to Porcine parvovirus (PPV). Groups 1, 3 and 4 pigs showed no evidence of infection or seroconversion associated with the tested viruses or any other pathogens found in the liquid plasma before UV-C irradiation. Group 5 pigs developed PCV-2 infectivity as expected. UV-C irradiation of liquid plasma at 3000 and 9000 J/L was effective in preventing PRRSV and other pathogens transmission. Moreover, raw liquid plasma was non-infectious for PCV-2 in naïve pigs.

Retrospective detection of Porcine circovirus 3 (PCV-3) in pig serum samples from Spain.

Porcine circovirus 3 (PCV-3) is an emerging circovirus species that has recently been reported in different countries around the world, suggesting a widespread circulation. In this study, sera samples originating from 654 pigs of different production phases and clinical/pathological conditions, submitted for diagnostic purposes between 1996 and 2017, were randomly selected. Detection of PCV-3 genome in such samples was attempted with a previously described PCR method, and the partial genome sequence was obtained from selected PCV-3-positive samples from different years. Compiled data confirmed that PCV-3 has been circulating in the Spanish pig population since 1996. The overall frequency of PCV-3 PCR-positive samples in the study period was 11.47% (75 of 654). Phylogenetic analysis of twelve PCV-3 partial sequences obtained showed a high nucleotide identity with the already known PCV-3 sequences, with minor variations among years. No significant correlation was found between the detection of PCV-3 and any production phase nor clinical/pathological condition. These results confirm PCV-3 circulation at least since 1996 in the Spanish pig population with a low/moderate frequency. Although the information obtained was limited, PCV-3 did not appear to be linked to any specific pathological condition or age group.

Update on Mycoplasma hyopneumoniae infections in pigs: Knowledge gaps for improved disease control.

Mycoplasma hyopneumoniae (M. hyopneumoniae) is the primary pathogen of enzootic pneumonia, a chronic respiratory disease in pigs. Infections occur worldwide and cause major economic losses to the pig industry. The present paper reviews the current knowledge on M. hyopneumoniae infections, with emphasis on identification and analysis of knowledge gaps for optimizing control of the disease. Close contact between infected and susceptible pigs is the main route of M. hyopneumoniae transmission. Management and housing conditions predisposing for infection or disease are known, but further research is needed to better understand M. hyopneumoniae transmission patterns in modern pig production systems, and to assess the importance of the breeding population for downstream disease control. The organism is primarily found on the mucosal surface of the trachea, bronchi and bronchioles. Different adhesins and lipoproteins are involved in the adherence process. However, a clear picture of the virulence and pathogenicity of M. hyopneumoniae is still missing. The role of glycerol metabolism, myoinositol metabolism and the Mycoplasma Ig binding protein-Mycoplasma Ig protease system should be further investigated for their contribution to virulence. The destruction of the mucociliary apparatus, together with modulating the immune response, enhances the susceptibility of infected pigs to secondary pathogens. Clinical signs and severity of lesions depend on different factors, such as management, environmental conditions and likely also M. hyopneumoniae strain. The potential impact of strain variability on disease severity is not well defined. Diagnostics could be improved by developing tests that may detect virulent strains, by improving sampling in live animals and by designing ELISAs allowing discrimination between infected and vaccinated pigs. The currently available vaccines are often cost-efficient, but the ongoing research on developing new vaccines that confer protective immunity and reduce transmission should be continued, as well as optimization of protocols to eliminate M. hyopneumoniae from pig herds.

Assessment of Mycoplasma hyopneumoniae-induced Pneumonia using Different Lung Lesion Scoring Systems: a Comparative Review.

Mycoplasma hyopneumoniae is the primary aetiological agent of swine enzootic pneumonia (EP) and one of the major contributors to the porcine respiratory disease complex (PRDC). Gross lung lesions in pigs affected by EP consist of cranioventral pulmonary consolidation (CVPC), usually distributed bilaterally in the apical, intermediate, accessory and cranial parts of the diaphragmatic lobes. Several lung scoring methods are currently in place for the evaluation of CVPC. The aims of this study were (1) to review the lung lesion scoring systems used to assess pneumonia associated with M. hyopneumoniae infection, and (2) to evaluate eight of these scoring systems by applying them to the lungs of 76 pigs with experimentally-induced M. hyopneumoniae pneumonia. A significant correlation between all lung lesion scoring systems was observed and the coefficients of determination in a regression analysis were very high between each pair-wise comparison, except for a unique scoring system based on image analysis. A formula of equivalence between lung scoring methods was developed in order to compare the results obtained with these methods. The present review provides a basis for comparison (even retrospectively) of lesions evaluated using different lung scoring systems.

Virological and serological characterization of vaccinated and non-vaccinated piglet subpopulations coming from vaccinated and non-vaccinated sows.

The present study describes the virological and serological profiles of PCV2 vaccinated (V) and non-vaccinated (NV) piglet subpopulations coming from V and NV sows in a PCV2 subclinically infected farm. Four hundred seventy-six piglets born from V or NV sows were further subdivided in a total of four groups: NV sows-NV pigs (NV-NV), NV sows-V pigs (NV-V); V sows-NV pigs (V-NV) and V sows-V pigs (V-V). Seventy-five pigs were randomly selected at the beginning of the trial from each group and they were bled at 4, 8, 12, 16, 21 and 25 weeks of age. All animals included in the trial were weighed at 4 and 25 weeks of age and their average daily weight gain (ADWG) was calculated. Serum samples obtained at different time points were used to assess PCV2 infection (viremia) and the level of antibodies by means of immunoperoxidase monolayer assay (IPMA) against this pathogen. IPMA titers (classified in high, medium or low) and PCR results (positive or negative) were analyzed using a multiple correspondence and K-means cluster analysis. According to these tests, animals included in the study were classified into the following four clusters: (1) 93 piglets that were viremic mainly from 12 to 25 weeks of age and with PCV2 antibody titers increasing over time; (2) 75 piglets with late PCV2 infection and seroconversion (later than 16 weeks of age); (3) 26 piglets with high but decreasing PCV2 antibody titers and low percentages of PCV2 PCR positive serum samples; and (4) 105 piglets with medium and high IPMA titers throughout the trial and sporadic PCR positive samples. The defined subpopulations of piglets were observed in all experimental groups (NV-NV, NV-V, V-NV and V-V) although in variable percentages. Thus, animals from clusters 1 and 2 belonged mainly to the NV-NV and V-NV groups and animals from clusters 3 and 4 were distributed mainly into the NV-V and V-V groups. Finally, the ADWG of pigs belonging to clusters 3 and 4 was significantly higher (p=0.02) than that of pigs belonging to clusters 1 and 2. Within each cluster, no statistically significant differences were found in ADWG between treatment groups.

Effect of porcine circovirus type 2 (PCV2) load in serum on average daily weight gain during the postweaning period.

Porcine circovirus type 2 (PCV2) is a ubiquitous virus that mainly affects nursery and fattening pigs causing systemic disease (PCV2-SD) or subclinical infection. A characteristic sign in both presentations is reduction of average daily weight gain (ADWG). The present study aimed to assess the relationship between PCV2 load in serum and ADWG from 3 (weaning) to 21 weeks of age (slaughter) (ADWG 3-21). Thus, three different boar lines were used to inseminate sows from two PCV2-SD affected farms. One or two pigs per sow were selected (60, 61 and 51 piglets from Pietrain, Pietrain×Large White and Duroc×Large White boar lines, respectively). Pigs were bled at 3, 9, 15 and 21 weeks of age and weighted at 3 and 21 weeks. Area under the curve of the viral load at all sampling times (AUCqPCR 3-21) was calculated for each animal according to standard and real time quantitative PCR results; this variable was categorized as "negative or low" (<10(4.3) PCV2 genome copies/ml of serum), "medium" (≥10(4.3) to ≤10(5.3)) and "high" (>10(5.3)). Data regarding sex, PCV2 antibody titre at weaning and sow parity was also collected. A generalized linear model was performed, obtaining that paternal genetic line and AUCqPCR 3-21 were related to ADWG 3-21. ADWG 3-21 (mean±typical error) for "negative or low", "medium" and "high" AUCqPCR 3-21 was 672±9, 650±12 and 603±16 g/day, respectively, showing significant differences among them. This study describes different ADWG performances in 3 pig populations that suffered from different degrees of PCV2 viraemia.

Comparison of the immunoperoxidase monolayer assay and three commercial ELISAs for detection of antibodies against porcine circovirus type 2.

The aim of this study was to compare and correlate antibody titres against porcine circovirus type 2 (PCV2) in porcine sera (n = 1270) obtained by immunoperoxidase monolayer assay (IPMA) with the results of three commercial ELISAs (designated E1, E2 and E3). The correlation between IPMA and ELISA results was excellent (r(2) ≥ 0.90). Compared to IPMA, E2 had the highest sensitivity (93.0%), followed by E3 (90.1%) and E1 (85.0%); the specificity was 100% for all tests. All three commercial ELISAs had predictive values similar to those of IPMA and could be used to monitor antibody responses against PCV2 infection and/or vaccination.

Humoral response and colostral antibody transfer following 'one-dose' pre-mating vaccination of sows against porcine circovirus type-2.

The objective of this study was to investigate the presence of porcine circovirus type 2 (PCV2) DNA and antibody to the virus in the serum and colostrum of sows vaccinated prior to mating and in their offspring. Seventy-seven sows were randomly distributed into vaccinated (V, n=36) and non-vaccinated (NV, n=41) groups. One week before mating, sows were given a PCV2 vaccine (V group) or PBS (NV group) IM. Blood samples were taken from the sows at fixed time-points and colostrum samples were taken at farrowing. Blood samples were also taken from the piglets of the sows at 4 weeks of age. The results indicated that vaccination prior to mating elicited a strong, homogeneous humoral response and, in consequence, more homogeneous colostral PCV2 antibody concentrations.

Simultaneous porcine circovirus type 2 and Mycoplasma hyopneumoniae co-inoculation does not potentiate disease in conventional pigs.

The aim of this study was to assess the effect of simultaneous experimental inoculation of porcine circovirus type 2 (PCV2; intranasal delivery) and Mycoplasma hyopneumoniae (Mhyo; transtracheal delivery) into conventional, seropositive 6-week-old piglets. Thirty-six male piglets were assigned randomly to four groups: control (n=6), PCV2 (n=6), Mhyo (n=12) and PCV2+Mhyo (n=12). Blood samples and faecal and nasal swabs were collected at 0, 7, 14 and 21 days post inoculation (dpi). No significant clinical signs attributable to PCV2 infection were observed during the experiment. Coughing was recorded in three pigs from the Mhyo group and six from the PCV2+Mhyo group. No significant differences in mean body weight and rectal temperature were observed between the groups. Mild microscopical lesions similar to those reported for post-weaning multisystemic wasting syndrome were observed in two PCV2 pigs and in one PCV2+Mhyo animal. Mhyo-compatible lung lesions were observed in 21/24 pigs inoculated with Mhyo (10 from the Mhyo group and 11 from the PCV2+Mhyo group). PCV2 was detected by in-situ hybridization in 3/12 PCV2 and in 4/12 PCV2+Mhyo animals. No significant differences in PCV2 load (serum and nasal and faecal swabs), duration of viraemia or antibody titre were detected between PCV2-inoculated groups. No significant differences in Mhyo load in nasal swabs, percentage of Mhyo-seropositive pigs and mean lung score was detected between Mhyo-inoculated groups. Under the conditions of the present study, concurrent inoculation of PCV2 and Mhyo did not result in potentiation of clinical signs and lesions attributed to either infection.

Microarray analysis of mediastinal lymph node of pigs naturally affected by postweaning multisystemic wasting syndrome.

Postweaning multisystemic wasting syndrome (PMWS) is one of the pig diseases with major economic impact worldwide. Clinical, pathologic and some immunologic aspects of this disease are relatively well-known, but the molecular mechanisms underlying the pathogenic mechanisms of the disease are still poorly understood. The objective of the present study was to investigate the global transcriptome changes in the mediastinal lymph nodes from pigs naturally affected by PMWS, as well as healthy counterparts, using the Affymetrix Porcine Genechip(®). From 366 transcripts showing significant differential abundance in the PMWS group of pigs relative to healthy animals, 229 showed higher and 137 lower abundance. A relative increased abundance of mRNAs coded by a large set of genes involved in the inflammatory responses (e.g. cytokines, acute phase proteins, and respiratory burst) was observed in PMWS affected pigs. The Gpnmb and Lgals3 genes, which have antagonistic functions in regulation of inflammatory processes, showed high mRNA levels in diseased pigs. The complement system was altered by PMWS, notably by the lower levels of Cr1 mRNA, which might favour both complement deposition and secondary infections by impairing phagocytosis. Decreased mRNA abundance of several genes involved in lymphocyte activation/differentiation, such as Cd79b, Cd19, Cd21 and MybL1, and the high level of Vsig4 mRNA, which can compromise the activation of residing T-cells, pointed towards a defective adaptive immunity. This is the first study on gene expression in pigs naturally affected by PMWS. The present results allowed identifying potential mechanisms underlying the inflammation and lymphocyte depletion in lymphoid tissues by complement mediated damage and immunosuppression, which are key features of PMWS.

Lack of effect of piglet vaccination against Porcine circovirus type 2 (PCV2) on serum viral loads of Torque teno sus virus 2 (TTSuV2).

Anelloviruses are small, non-enveloped viruses with circular single stranded DNA, which infect a number of animal species as well as humans. In pigs, two distinct Torque teno sus virus (TTSuV) species have been described so far, being one of them linked to disease occurrence. Specifically, TTSuV2 loads in serum have been found increased in pigs suffering from postweaning multisystemic wasting syndrome (PMWS). Since this pathological condition is able to be controlled by means of porcine circovirus type 2 (PCV2) vaccination, it was hypothesized the possibility that such vaccination would have an impact on TTSuV2 prevalence and loads. A total of 150 pigs were divided in two study groups. Half of them received a PCV2 commercial vaccine, while the other half remained as non-vaccinated controls. PCV2 infection was monitored at 3-4, 8, 12, 16 and 21 weeks of age by means of an standard PCR, while TTSuV2 loads were determined at 8, 16 and 21 weeks of age by a quantitative PCR. No obvious PMWS clinical signs were observed among studied animals, although PCV2 infection was confirmed in both groups of pigs. Almost all pigs got TTSuV2 infection throughout the study period, independently of the PCV2 vaccination status of animals. Moreover, TTSuV2 load did not show significant differences between different pig groups at each sampling time, but mean viral load increased with age. Taking into account that previous results suggest that TTSuV2 load in serum is increased in the background of PMWS, the present study suggests that this is not the case in a PCV2 subclinical infection scenario. Therefore, vaccination of PCV2 subclinically infected pigs did not modify the outcome of TTSuV2 infection.

Torque teno sus virus 1 and 2 viral loads in postweaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS) affected pigs.

Torque teno viruses (TTV) are small, non-enveloped viruses with a circular single-stranded DNA genome, which are considered non-pathogenic. However, TTVs have been eventually linked to human diseases. TTVs infecting pigs, Torque teno sus virus 1 (TTSuV1) and 2 (TTSuV2), have been recently associated to porcine circovirus diseases (PCVD). To get more insights into such potential disease association, the aim of this study was to quantify TTSuV1 and TTSuV2 viral loads in serum of pigs affected by two PCVDs, postweaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS). Such study was carried out by means of a newly developed real-time quantitative PCR (qPCR) method. Both TTSuVs were highly prevalent among studied pigs. TTSuV2 viral loads were significantly higher in PMWS affected animals, further supporting the previously suggested association between TTSuV2 and PMWS. On the contrary, TTSuV1 prevalence and loads were not related with the studied PCVDs.

Genotypic shift of porcine circovirus type 2 from PCV-2a to PCV-2b in Spain from 1985 to 2008.

Changes in porcine circovirus type 2 (PCV-2) genotypes were evaluated before, during and after outbreaks of post-weaning multisystemic wasting syndrome (PMWS) in (1) a retrospective study using pig sera collected in Spain from 1985 to 2008 and (2) a longitudinal study using pig sera collected from two farms in Spain over periods of 7 and 14 years. In both studies, there was a rapid genotypic shift from PCV-2a to PCV-2b that was related to the peak of PMWS epizootics in Spain and the appearance of PMWS on the two farms studied longitudinally.

Duration of maternally derived antibodies in Toxoplasma gondii naturally infected piglets.

A longitudinal study was performed to analyze the dynamics of Toxoplasma gondii antibodies in naturally infected piglets from 1 to 25 weeks of age. Seventy-three piglets from 20 seronegative sows (modified agglutination test, MAT <1:25) and 20 naturally infected T. gondii seropositive sows (MAT >or=1:25) were analyzed at 1, 3, 6, 9, 12, 15, 18, 22 and 25 weeks of age. Twenty-six of the 73 piglets analyzed (35.6%; CI 95%: 25.5-45.7) were seropositive at some point during the study. Seroprevalence in piglets at 1 and 3 weeks of age was significantly higher in animals born from seropositive sows (P<0.001 and P=0.02, respectively) as an indication of maternally derived antibodies. The longest persistence (up to 6 weeks of age) was observed in piglets whose dam had high T. gondii antibody level (MAT >or=1:500), while persistence of maternally derived antibodies in the piglets born from sows with low antibody titers (maximum 1:50) was shorter and lasted only up to 3 weeks of age, when the piglets were weaned. The risk of horizontal transmission in piglets increased with age and was higher in piglets during the finishing period. The present results indicate that the decline of T. gondii maternally derived antibodies in naturally infected piglets is associated with the titers of their dams.

Serological, pathological and polymerase chain reaction studies on Mycoplasma hyopneumoniae infection in the wild boar.

There are evidences that wild boar and domestic pig populations share the vulnerability to certain pathogens and, in consequence, the risk of pathogen transmission. Based on serological evidences, it is known that Mycoplasma hyopneumoniae (Mhyo) is able to infect the wild boar. However, if this infection causes lesions and disease in this species is still unknown. The objectives of the present study were to assess the seroprevalence to Mhyo, as well as the rates of detection of Mhyo (by nested polymerase chain reaction, nPCR) in upper and lower respiratory tract of the wild boar. Moreover, presence of enzootic pneumonia (EP)-like gross and microscopic lesions in these animals was also assessed. Antibodies against Mhyo were detected in 92 out of 428 (21%) serum samples tested. Moreover, Mhyo DNA was detected by nPCR in 17 out of 85 (20%) nasal swabs and in 12 out of 156 (8%) lung samples. No gross EP-like lesions were observed in any of the studied pigs. Besides, presence of EP-like microscopic lung lesions was observed in 18 out of 63 (29%) animals. Mhyo DNA was detected at lung level in 2 out of these 18 (11%) animals. Presence of EP-like microscopic lesions was significantly related (p<0.05) with Mhyo detection at nasal swab swab but not (p>0.05) with its detection in lung samples; such lesions were also linked (p<0.05) with presence of Metastrongylus spp.-like parasite structures. Results of the present study confirm that Mhyo is able to infect and might be able to cause EP-like microscopic lesions in wild boar but, apparently, with a subclinical impact.

A genetically engineered chimeric vaccine against porcine circovirus type 2 (PCV2) improves clinical, pathological and virological outcomes in postweaning multisystemic wasting syndrome affected farms.

The present study describes the effects of a commercially available genetically engineered chimeric vaccine against porcine circovirus type 2 (PCV2) on clinical, pathological and virological features in three multi-site farms suffering from postweaning multisystemic wasting syndrome (PMWS). The vaccine product was able to reduce clinical signs, PCV2 viral load in lymphoid organs and/or sera, and overall mortality in nurseries and fattening units. This is the first time in which is shown that a PCV2 vaccine is able to decrease specifically PMWS-associated mortality. Another novelty of this study is the assessment of PMWS-like histological lesions in a large number of vaccinated and non-vaccinated pigs under field conditions.

Swine torque teno virus (TTV) infection and excretion dynamics in conventional pig farms.

Torque teno virus (TTV) is a non-enveloped, single-stranded DNA (ssDNA) virus infecting human and non-primate species. Two genogroups of TTV (TTV1 and TTV2) have been described in swine so far. In the present study, TTV1 and TTV2 prevalences in serum, and nasal as well as rectal swabs of 55 randomly selected piglets from seven Spanish multi-site farms, were monitored from 1 to 15 weeks of age. Also, blood from their dams (n=41) were taken at 1 week post-farrowing. Samples were tested by means of two TTV genogroup specific PCRs. Although prevalence of TTV1 and TTV2 in sows was relatively high (54% and 32%, respectively), it was not directly associated to their prevalence in the offspring. Percentage of viremic pigs for both TTV genogroups followed similar dynamics, increasing progressively over time, with the highest rate of detection at 11 weeks of age for TTV1 and at 15 weeks for TTV2. Forty-two (76%) and 33 (60%) of the 55 studied pigs were TTV1 and TTV2 PCR positive in serum, respectively, in more than one sampling time. TTV1 and TTV2 viremia lasted in a number of animals up to 15 and 8 weeks, respectively. Co-infection with both TTV genogroups in serum was detected at all sampling points, but at 1 week of age. On the contrary, there were animals PCR negative to both genogroups in serum at all sampling times but at 15 weeks of age. During the study period, TTV1 and TTV2 nasal shedding increased also over time and faecal excretion was intermittent and of low percentage (<20%). In conclusion, the present study describes for the first time the infection dynamics of TTV1 and TTV2 as well as the nasal and faecal excretion throughout the life of pigs from conventional, multi-site farms. Moreover, results indicate that both swine TTV genogroups are able to establish persistent infections in a number of pigs.

Exploratory study on the transcriptional profile of pigs subclinically infected with porcine circovirus type 2.

The aim of this exploratory work was to use a microarray-based approach to study the global transcriptome profile of caesarean-derived, colostrum-deprived (CDCD) piglets experimentally infected with porcine circovirus type 2 (PCV2). PCV2-inoculated piglets developed a subclinical infection, as confirmed by serology, in situ hybridization and quantitative PCR. Total RNA from mesenteric lymph nodes and lungs was obtained by duplicate from 2 control and 2 PCV2-inoculated piglets and was hybridized to Affymetrix Porcine GeneChip. Among the 24,123 probesets studied, 25 and 33 were found to be significantly differentially expressed (DE) between control and PCV2 groups for mesenteric lymph node and lung, respectively. Most up-regulated genes in PCV2 group were closely related to the immune response, such as cytokines (CCL4L, CXCL9, CXCL11), MHC binding molecules (TCRalpha, CD8alpha), immunoglubulins (IgG) and T cell activation (LCK, KLRK1, RASSF2, GBP2). Quantitative real-time PCR was performed to verify the microarray results. Therefore, from a transcriptional point of view, PCV2-inoculated pigs were apparently able to activate a cell-mediated response and develop PCV2-specific antibodies, which probably led to a subclinical infection. The results from this study indicate that a microarray based approach is a helpful tool in order to better understand the pathogenesis of PCV2 infection.