The first isolation of porcine circovirus type 2e from a Korean pig.

This study describes the first isolation and genetic characterization of the newly emerging porcine circovirus type 2e (PCV2e) from Korean pigs. The PCV2e isolate did not produce a cytopathic effect in PCV-free PK-15 cells; therefore, PCV2e infection was demonstrated by immunohistochemistry with polyclonal PCV2a antibodies and polymerase chain reaction with primers specific for PCV2e. As the infected PCV-free PK-15 cells were passaged, the amount of infectious virus correlated with an increase in the amount of viral DNA (i.e., a decrease in the cycle threshold values. A full genomic analysis of the PCV2e strain SNUVR199711 was performed and showed that the genome is 1,777 nucleotides in length.

Importance of sequential infection order of porcine circovirus type 2 and porcine reproductive and respiratory syndrome virus to divergent clinical outcomes.

This study was designed to investigate the different sequential order of infection for porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV). Thirty-six pigs were randomly assigned to six different treatment groups. The first (hereafter referred to as PRRSV-PCV2) group was inoculated with PRRSV first followed by PCV2d. The second (hereafter referred to as PCV2+PRRSV) group was co-infected with both viruses at the same timepoint (42 days of age). The third (hereafter referred to as PCV2-PRRSV) group was inoculated with PCV2d first followed by PRRSV. A fourth group was only inoculated with PCV2d at 42 days of age, while a fifth group was only inoculated with PRRSV at the same timepoint. The sixth group served as a negative control group. The most important observation discovered that PRRSV only had a potentiation effect on PCV2 in both PRRS-PCV2 and PCV2+PRRSV groups. Both PRRSV-PCV2 and PCV2+PRRSV groups experienced a significant reduction in growth performance compared with control pigs. In addition, PRRSV-PCV2 and PCV2+PRRSV groups exhibited a greater severity in their clinical signs, and/or had higher PCV2 blood and lymphoid viral loads that resulted in a stronger severity of lymphoid lesions compared with PCV2-PRRSV group. Serum TNF-α levels were significantly higher in both PRRS-PCV2 and PCV2+PRRSV groups compared with those in PCV2-PRRS, PCV2, and PRRSV groups. The results of this study demonstrated that divergent clinical outcomes are dependent on the sequential infection order of PCV2 and PRRSV.

Field efficacy of a recombinant toxoid vaccine against Shiga toxin 2e during a naturally occurring edema disease infection.

The objective of this field trial was to determine the efficacy of a recombinant toxoid vaccine against Shiga toxin 2e (Stx2e) in piglets suffering from edema disease (ED). Three farms with confirmed ED cases were selected for the field trials. On each farm, a total of 40 4-day-old pigs were randomly allocated to either the vaccinated or unvaccinated group, with 20 pigs per group (10 males and 10 females). A 1.0-mL dose of the recombinant toxoid vaccine was administered intramuscularly to pigs in the vaccinated groups in accordance with the manufacturer's recommendations at 4 d of age. A single 2.0-mL dose of phosphate-buffered saline was administered to unvaccinated pigs at the same age. Clinical signs of ED were observed in 12 piglets in the unvaccinated groups and 7 unvaccinated pigs died as a result of ED out of the total number of piglets on Farms A, B, and C. Vaccination had a positive effect on pig growth performance compared to that of unvaccinated pigs on 2 of the 3 farms. Seroconversion of neutralizing antibodies against Stx2e occurred in 70% of piglets in the vaccinated group on Farm A, 75% of vaccinated piglets on Farm B, and 55% of vaccinated piglets on Farm C, when detectable antibodies were measured at 17 d post-vaccination (dpv). Detectable antibodies were measured in 85% of vaccinated piglets on Farms A and B and in 90% of these piglets on Farm C at 37 dpv. These field trials determined that the ED recombinant toxoid vaccine successfully reduced clinical signs and mortality, improved average daily weight gain, and resulted in the production of neutralizing antibodies against Stx2e in pigs.

L'objectif de cette étude sur le terrain était de déterminer l'efficacité d'un vaccin à base d'anatoxine recombinante contre la toxine Shiga 2e (Stx2e) chez les porcelets souffrant de la maladie de l'oedème (ED). Trois fermes ayant des cas confirmés de ED ont été sélectionnées pour les études sur le terrain. Dans chaque ferme, un total de 40 porcs âgés de 4 jours ont été répartis au hasard dans le groupe vacciné ou non vacciné, avec 20 porcs par groupe (10 mâles et 10 femelles). Une dose de 1,0 ml du vaccin à base d'anatoxine recombinante a été administrée par voie intramusculaire aux porcs des groupes vaccinés conformément aux recommandations du fabricant à l'âge de 4 jours. Une dose unique de 2,0 ml de solution saline tamponnée au phosphate a été administrée aux porcs non vaccinés au même âge. Des signes cliniques de ED ont été observés chez 12 porcelets des groupes non vaccinés et 7 porcs non vaccinés sont morts des suites d'une maladie de l'oedème sur le nombre total de porcelets des fermes A, B et C. La vaccination a eu un effet positif sur les performances de croissance des porcs par rapport à celles des porcs non vaccinés dans 2 des 3 fermes. La séroconversion des anticorps neutralisants contre Stx2e s'est produite chez 70 % des porcelets du groupe vacciné de la ferme A, 75 % des porcelets vaccinés de la ferme B et 55 % des porcelets vaccinés de la ferme C, lorsque des anticorps détectables ont été mesurés 17 jours après la vaccination (dpv). Des anticorps détectables ont été mesurés chez 85 % des porcelets vaccinés des fermes A et B et chez 90 % de ces porcelets de la ferme C à 37 dpv. Ces études sur le terrain ont déterminé que le vaccin toxoïde recombinant ED réduisait avec succès les signes cliniques et la mortalité, améliorait le gain de poids quotidien moyen et entraînait la production d'anticorps neutralisants contre Stx2e chez les porcs.(Traduit par Docteur Serge Messier).

Comparison of pathogenicity of 4 porcine circovirus type 2 (PCV2) genotypes (2a, 2b, 2d, and 2e) in experimentally infected pigs.

The objective of the current study was to compare the virulence of four porcine circovirus type 2 (PCV2) genotypes (PCV2a, 2b, 2d, and 2e) in pigs. Pigs were inoculated at 42 days of age with one of four PCV2 genotypes, then necropsied at 63 days of age. PCV2 genotype groups were evaluated through a comparison of clinical outcomes, antibody titers, level of PCV2 loads in blood and lymph nodes, and lymphoid lesion severity. Statistical differences did not occur between the evaluated genotype groups. Pigs inoculated with PCV2a, PCV2b, or PCV2d had a significantly (P<0.05) higher levels of PCV2 loads in blood and lymph node compared to pigs inoculated with PCV2e. The results of this study indicated that the PCV2a, PCV2b, and PCV2d are more virulent than PCV2e based on blood and lymphoid viral load of PCV2.

Field evaluation of novel plant-derived porcine circovirus type 2 vaccine related to subclinical infection.

BACKGROUND: The objective of this field trial was to evaluate the efficacy of a new plant-based porcine circovirus type 2a (PCV2a) vaccine. This vaccine was a recombinant capsid subunit PCV2a vaccine based on the Nicotiana benthamiana expression system. METHODS: Three farms were selected for the study based on their history of subclinical PCV2 infection. A total of 40 18-day-old pigs were randomly allocated to either vaccinated or unvaccinated groups (20 pigs per group; 10 = male and 10 = female). Pigs received a 2.0-mL dose of the plant-based PCV2a vaccine intramuscularly at 21 days of age in accordance with the manufacturer's recommendations, whereas unvaccinated pigs were administered a single dose of phosphate buffered-saline at the same age. RESULTS: Vaccination had a positive effect on pig growth performance compared to that of unvaccinated pigs on all three of the farms. Vaccination of pigs with a plant-based PCV2a vaccine induced high levels of neutralizing antibodies titres against PCV2d and PCV2d-specific interferon-γ secreting cells which resulted in the reduction of PCV2d viral load and reduced lymphoid lesions severity. CONCLUSIONS: The results of this field trial demonstrated cross-protection of PCV2d by a plant-based PCV2a vaccine and a positive effect of pig growth performance with vaccination.

Virulence Comparison of Four Porcine Circovirus Type 2 (PCV2) Genotypes (2a, 2b, 2d and 2e) in Pigs Single-Infected with PCV2 and Pigs Dual-Infected with PCV2 and Mycoplasma hyopneumoniae.

The objective of this study was to compare the virulence of four porcine circovirus type 2 (PCV2) genotypes (2a, 2b, 2d and 2e). Pigs were infected with one of these four genotypes. Pigs were also dually infected with Mycoplasma hyopneumoniae and one of the four PCV2 genotypes. Virulence was determined based on the amount of PCV2 loads in the blood and lymph nodes and the severity of lymphoid lesions. Marked differences in virulence were found among the four genotypes. Within the single infection model, PCV2a, PCV2b and PCV2d were more virulent than PCV2e, while significant differences in virulence were not found among the PCV2a, PCV2b and PCV2d groups. Within the dual infection model, PCV2d was more virulent than the other three PCV2 genotypes. Mycoplasma hyopneumoniae potentiated the severity of PCV2-associated lymphoid lesions and increased the amount of PCV2 loads in the blood and lymph nodes, regardless of the PCV2 genotype. By contrast, PCV2 was not able to potentiate the severity of mycoplasmal-induced lung lesions or the level of M. hyopneumoniae laryngeal load. The results of this study demonstrate that PCV2d is of major clinical importance, while PCV2e is of minor clinical importance.

A Comparative Field Evaluation of the Effect of Growth Performance Between Porcine Circovirus Type 2a (PCV2a)- and PCV2b-Based Bivalent Vaccines Containing PCV2 and Mycoplasma hyopneumoniae.

The objective of this study was to compare two different bivalent vaccines containing porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae. One vaccine contained PCV2a and the other contained PCV2b, and both were administered on a farm suffering from subclinical PCV2d infection and enzootic pneumonia. A total of 180 pigs were randomly divided into 3 groups (60 pigs per group; male pigs = 30 and female pigs = 30). Bivalent vaccination significantly improved growth performance in both vaccinated groups as compared to the unvaccinated (UnVac) group. Growth performance measured by body weight and average daily weight gain (ADWG) was not significantly different between the two bivalent-vaccinated groups (VacA and VacB). Both bivalent vaccines elicited high levels of neutralizing antibodies and interferon-γ secreting cells (IFN-γ-SC) against PCV2d, leading to a reduction in the levels of PCV2d blood viral load as compared to unvaccinated animals. Similarly, both bivalent vaccines elicited high levels of IFN-γ-SC against M. hyopneumoniae that reduced the level of M. hyopneumoniae laryngeal viral loads as compared to unvaccinated animals. Significant differences in severity of lung and lymphoid lesions were observed in both vaccinated groups as compared to the UnVac group. These comparative field data demonstrated that both bivalent vaccines are good candidates for controlling subclinical PCV2d infection and enzootic pneumonia in swine farms suffering from an existing infection.

Multiplex polymerase chain reaction for the detection and differentiation of 4 porcine circovirus 2 genotypes (PCV-2a, -2b, -2d, and -2e) in clinical samples.

The objective of this study was to develop multiplex polymerase chain reaction (PCR) for the simultaneous detection of porcine circovirus 2 (PCV-2) and differentiation among 4 PCV-2 genotypes (2a, 2b, 2d, and 2e) in collected clinical lymph node samples. The multiplex PCR detected each of 4 PCV-2 genotypes (2a, 2b, 2d, and 2e) to a dilution of 2 × 101 copies/µL. PCV-2a, PCV-2b, PCV-2d, and PCV-2e were propagated in tissues prior to DNA extraction for use in multiplex PCR for the simultaneous detection and differentiation of 4 PCV-2 genotypes. The designed multiplex PCR effectively detected and differentiated various combinations of multiple infection, such as PCV-2a+2b, PCV-2a+2d, PCV-2b+2d, PCV-2a+2e, and PCV-2a+2b+2d, in clinical lymph node samples. The results of this study demonstrated that multiplex PCR testing of clinical samples developed herein was able to simultaneously detect and differentiate among the 4 PCV-2 genotypes (PCV-2a, 2b, 2d, and 2e).

L'objectif de cette étude était de développer une réaction en chaîne par la polymérase multiplex (PCR) pour la détection simultanée du circovirus porcin 2 (PCV-2) et la différenciation entre quatre génotypes PCV-2 (2a, 2b, 2d et 2e) dans des échantillons cliniques de noeuds lymphatique. La PCR multiplex a détecté chacun des quatre génotypes PCV-2 (2a, 2b, 2d et 2e) à une dilution de 2 × 101 copies/µL. Le PCV-2a, le PCV-2b, le PCV-2d et le PCV-2e ont été propagés dans les tissus avant l'extraction de l'ADN pour être utilisés dans la PCR multiplex pour la détection et la différenciation simultanées de quatre génotypes du PCV-2. La PCR multiplex conçue a efficacement détecté et différencié diverses combinaisons d'infections multiples, telles que PCV-2a+2b, PCV-2a+2d, PCV-2b+2d, PCV-2a+2e et PCV-2a+2b+2d, dans les échantillons cliniques de ganglions lymphatiques. Les résultats de cette étude ont démontré que le test PCR multiplex des échantillons cliniques développés ici était capable de détecter et de différencier simultanément les quatre génotypes PCV-2 (PCV-2a, 2b, 2d et 2e).(Traduit par Docteur Serge Messier).

Non-Inferiority Field Study Comparing the Administrations by Conventional Needle-Syringe and Needle-Free Injectors of a Trivalent Vaccine Containing Porcine Circovirus Types 2a/2b and Mycoplasma hyopneumoniae.

The objective of this study was to assess the clinical, immunological, microbiological, and pathological evaluation of trivalent vaccine containing porcine circovirus types 2a/b (PCV2a/b) and Mycoplasma hyopneumoniae given by two different needle-free injection devices compared with conventional needle-syringe injection in a herd with subclinical PCV2d infection and enzootic pneumonia. A total of 240 21-day-old pigs, which weighed between 5 to 6 kg, were randomly divided into four groups (60 pigs per group, 30 = male and 30 = female per group). Injection site reactions in the pigs were minimal for the two needle-free injection devices and needle-syringe injection. Trivalent vaccination of pigs with two needle-free injection devices was not inferior to conventional needle-syringe injection for growth performance. Trivalent vaccination of pigs with two different needle-free injection devices reduced levels of PCV2d loads in serum and M. hyopneumoniae loads in the larynx equally compared to the conventional needle-syringe injection. The amount of PCV2d load in serum from the needle-free Pulse FX injection device at 49 days post vaccination showed non-inferiority to conventional needle-syringe injection. The immune response against PCV2 and M. hyopneumoniae to trivalent vaccine given with the needle-free Pulse FX injection device was non-inferior to conventional needle-syringe injection. The pigs from the two needle-free injection device and conventional needle-syringe injection had significantly (p < 0.05) lower macroscopic and microscopic lung lesion scores, and microscopic lymphoid lesions than from unvaccinated. The results of this study demonstrated that vaccination of trivalent vaccine by the two needle-free Pulse injection devices used in the study was non-inferior to that by conventional needle-syringe injection for growth performance, immune response against PCV2 and M. hyopneumoniae, and reduction of PCV2 viremia.

Efficacy test of a plant-based porcine circovirus type 2 (PCV2) virus-like particle vaccine against four PCV2 genotypes (2a, 2b, 2d, and 2e) in pigs.

The objective of this study was to evaluate the efficacy of a recombinant porcine circovirus type 2 (PCV2) vaccine based from a Nicotiana benthamiana expression system against four different co-challenges with PCV2 genotypes (2a, 2b, 2d, and 2e) and porcine reproductive and respiratory syndrome virus (PRRSV). Pigs in the vaccinated groups each received a 1.0 mL intramuscularly of plant-based PCV2a vaccine in the neck muscle at 21 days of age. Vaccinates were then co-challenged with a combination of one of four PCV2 genotypes (2a, 2b, 2d, and 2e) and PRRSV at 42 days of age. Regardless of the PCV2 genotype used for challenge, vaccination significantly reduced clinical signs, reduced the level of PCV2 load in both blood and lymph nodes, and reduced the severity of lymphoid lesions in pigs. Vaccination resulted in significantly higher titers of neutralizing antibody against the corresponding PCV2 genotype evaluated and increased the frequency of PCV2-specific interferon-γ secreting cells. The results of this study demonstrated that a plant-based PCV2 vaccine conferred protection against a dual challenge with four different PCV2 genotypes when combined with PRRSV based on clinical, virological, immunological and pathological evaluation.

A field efficacy trial of a trivalent vaccine containing porcine circovirus type 2a and 2b, and Mycoplasma hyopneumoniae in three herds.

BACKGROUND: This field trial was designed to evaluate the efficacy of a new trivalent vaccine containing porcine circovirus type 2a and 2b (PCV2a/b), and Mycoplasma hyopneumoniae at three independent locations. METHODS: Three farms were selected based on their history of PCV2 and M. hyopneumoniae co-infection. Each farm housed a total of 60, 3-day-old pigs that were randomly allocated to one of three treatment groups. Pigs were administered the trivalent vaccine intramuscularly with either a 1.0 ml dose at 3 and 24 days of age or a 2.0 ml dose at 21 days of age in accordance with the manufacturer's recommendations. RESULTS: Clinically, the average daily weight gain of the one-dose and two-dose vaccinated groups within all three farms was significantly higher (p < 0.05) than those of unvaccinated animals during the growing (70-112 days of age), finishing (112-175 days of age) and overall (3-175 days of age) stages of production. One-dose and two-dose vaccinated animals elicited neutralizing antibodies and interferon-γ-secreting cells (IFN-γ-SC), which reduced the amount of PCV2 in terms of blood load and reduced the severity of lymphoid lesions when compared with unvaccinated animals. Similarly, one-dose and two-dose vaccinated animals elicited IFN-γ-SC, which reduced the amount of M. hyopneumoniae in terms of laryngeal load and reduced the severity of lung lesions. CONCLUSIONS: The intramuscular administration of either one or two doses of trivalent vaccine was not significantly different in any of the evaluated parameters. The results of field trial demonstrated that the trivalent vaccine was efficacious in the protection of swine herds where PCV2d and M. hyopneumoniae were in active circulation.

Comparative growth performance of 3 types of combination vaccines containing porcine circovirus 2 and Mycoplasma hyopneumoniae under field conditions.

The objective of this field trial was to compare the effect of 3 different types of combination vaccines on growth performance in pigs under field conditions. The vaccines compared were: a trivalent vaccine containing porcine circovirus type 2a and 2b (PCV-2a/b); and Mycoplasma hyopneumoniae; a mixable bivalent vaccine containing PCV-2a and M. hyopneumoniae; and a ready-to-use bivalent vaccine containing PCV-2a and M. hyopneumoniae. Two farms were selected on the basis of their history of subclinical PCV-2d infection and enzootic pneumonia. A total of 120 pigs on each farm was randomly divided into 4 groups of 30 pigs each. The trivalent-vaccinated group from both farms outperformed each bivalent-vaccinated group in terms of growth performance. Growth performance was significantly improved during the fattening period (70 to 175 d of age) in the mixable bivalent-vaccinated group compared with the ready-to-use bivalent-vaccinated group on 1 farm. The trivalent-vaccinated group elicited higher levels of neutralizing antibodies and interferon-γ secreting cells (IFN-γ-SC) against PCV-2d, while simultaneously decreasing the levels of PCV-2d load in blood when compared with the mixable and ready-to-use bivalent-vaccinated groups. The trivalent-vaccinated group also elicited higher levels of IFN-γ-SC against M. hyopneumoniae and lower levels of M. hyopneumoniae load in the larynx when compared with the mixable and ready-to-use bivalent-vaccinated groups. The results of the present study demonstrated that a trivalent vaccine containing PCV-2a/b and M. hyopneumoniae resulted in a more productive parameter, higher immune responses, and less blood-viral and mycoplasmal larynx-loads when compared with the mixable and ready-to-use bivalent vaccines despite the presence of ongoing subclinical PCV-2d infection and enzootic pneumonia on the farms.

L'objectif de cet essai de terrain était de comparer l'effet de trois différents types de vaccins combinés sur les performances de croissance chez les porcs dans des conditions de terrain. Les vaccins comparés étaient : un vaccin trivalent contenant des circovirus porcins de type 2a et 2b (PCV-2a/b) et Mycoplasma hyopneumoniae; un vaccin bivalent mélangeable contenant PCV-2a et M. hyopneumoniae; et un vaccin bivalent prêt à l'emploi contenant le PCV-2a et M. hyopneumoniae. Deux fermes ont été sélectionnées sur la base de leurs antécédents d'infection subclinique par le PCV-2d et de pneumonie enzootique. Un total de 120 porcs dans chaque ferme a été divisé au hasard en quatre groupes de 30 porcs chacun. Le groupe vacciné par les trivalents des deux fermes a surpassé chaque groupe vacciné par les bivalents en termes de performances de croissance. Les performances de croissance ont été significativement améliorées pendant la période d'engraissement (70 à 175 jours d'âge) dans le groupe vacciné bivalent mélangeable par rapport au groupe vacciné bivalent prêt à l'emploi sur une ferme. Le groupe vacciné par trivalent a suscité des niveaux plus élevés d'anticorps neutralisants et de cellules sécrétant de l'interféron-γ (IFN-γ-SC) contre le PCV-2d, tout en diminuant simultanément les niveaux de charge de PCV-2d dans le sang par rapport aux vaccins mélangeables et prêts à l'emploi. Le groupe vacciné trivalent a également provoqué des niveaux plus élevés d'IFN-γ-SC contre M. hyopneumoniae et des niveaux inférieurs de charge de M. hyopneumoniae dans le larynx par rapport aux groupes vaccinés bivalents mélangeables et prêts à l'emploi. Les résultats de la présente étude ont démontré qu'un vaccin trivalent contenant du PCV-2a/b et M. hyopneumoniae entraînait un paramètre plus productif, des réponses immunitaires plus élevées et moins de charges sanguines virales et mycoplasmiques dans le larynx par rapport aux vaccins mélangeables et prêts à l'emploi malgré la présence d'une infection subclinique par le PCV-2d et d'une pneumonie enzootique dans les élevages.(Traduit par Docteur Serge Messier).

Experimental evaluation of Mycoplasma hyopneumoniae bacterin against a Korean M. hyopneumoniae challenge.

The objective of this study was to evaluate the efficacy of a new Mycoplasma hyopneumoniae bacterin against a Korean M. hyopneumoniae challenge under experimental conditions. Fifteen pigs were allocated randomly into 3 groups (5 pigs per group) that were designated in 1 of 3 ways: vaccinated-challenged, unvaccinated-challenged, or unvaccinated-unchallenged. The pigs in the vaccinated-challenged group were immunized with an M. hyopneumoniae whole-cell bacterin at a 1.0 mL dose-level at 21 d old. At 42 d old (0 d post-challenge), the pigs in the vaccinated-challenged and unvaccinated-challenged groups were inoculated intranasally with a strain of Korean M. hyopneumoniae. Vaccinated-challenged pigs elicited a strong cell-mediated immunity as measured by M. hyopneumoniae-specific interferon-γ secreting cells when compared with unvaccinated-challenged pigs. Vaccination of pigs with this new M. hyopneumoniae bacterin reduced nasal shedding and lung lesions. The evaluated vaccine was therefore considered effective in controlling M. hyopneumoniae infection.

L'objectif de cette étude était d'évaluer l'efficacité d'une nouvelle bactérine de Mycoplasma hyopneumoniae contre une infection défi avec une souche coréenne de M. hyopneumoniae dans des conditions expérimentales. Quinze porcs ont été répartis au hasard en trois groupes (5 porcs par groupe) qui ont été désignés de l'une des trois façons suivantes : vaccinés-infectés, non vaccinés-infectés, non vaccinésnon infectés. Les porcs du groupe vacciné-infectés ont été immunisés avec 1,0 mL d'une bactérine à cellules entières de M. hyopneumoniae à 21 jours d'âge. A l'âge de 42 jours (0 jour après la provocation), les porcs dans les groupes vaccinés-infectés et non vaccinés-infectés ont été inoculés par voie intranasale avec une souche coréenne de M. hyopneumoniae. Les porcs vaccinés-infectés ont manifesté une forte immunité à médiation cellulaire telle que mesurée par les cellules sécrétant l'interféron-γ spécifique à M. hyopneumoniae par rapport aux porcs non vaccinés-infectés. La vaccination des porcs avec cette nouvelle bactérine de M. hyopneumoniae a réduit l'excrétion nasale et les lésions pulmonaires. Le vaccin évalué a donc été considéré comme efficace pour maitriser l'infection à M. hyopneumoniae.(Traduit par Docteur Serge Messier).

A Comparison of Virulence of Three Porcine Circovirus Type 2 (PCV2) Genotypes (a, b, and d) in Pigs Singularly Inoculated with PCV2 and Dually Inoculated with PCV2 and Porcine Reproductive and Respiratory Syndrome Virus.

The aim of this study was to compare the virulence of porcine circovirus type 2 (PCV2) genotypes in dually inoculated pigs with both three genotypes (a, b, and d) of PCV2 and porcine reproductive and respiratory syndrome virus-2 (PRRSV-2) versus pigs singularly inoculated with the same three PCV2 genotypes (a, b, and d). Differences in this comparison were found in PCV2 viremia levels, lung and lymphoid lesion severity, and the amount of PCV2 antigen within the lymphoid lesions. Regardless of PCV2 genotypes, pigs that were dually inoculated with PCV2/PRRSV had significantly higher clinical scores, less average daily weight gain, higher levels of PCV2 viremia, and more severe lug and lymphoid lesions compared to pigs singularly inoculated with PCV2. Among the dually infected pig groups, pigs infected with PCV2d/PRRSV-2 had significantly higher levels of PCV2 viremia, more severe lung and lymphoid lesions, and more PCV2-positive cells within lymphoid lesions compared to pigs dually inoculated with PCV2a/PRRSV-2 and PCV2b/PRRSV-2. The results of this study demonstrated significant differences in the virulence among dual inoculation of PCV2a/PRRSV-2, PCV2b/PRRSV-2, and PCV2d/PRRSV-2. A significant difference in the virulence among PCV2a, PCV2b, and PCV2d single-inoculated pig groups was not found with respect to the levels of PCV2 viremia and production of PCV2-associated lymphoid lesions.

Efficacy Evaluation of a Bivalent Vaccine Containing Porcine Circovirus Type 2b and Mycoplasma hyopneumoniae Against an Experimental Dual Challenge.

The purpose of this study was to evaluate the efficacy of a new, single-dose bivalent vaccine containing porcine circovirus type 2b (PCV2b) and Mycoplasma hyopneumoniae against a dual PCV2b and M. hyopneumoniae challenge. At -25 days post challenge (dpc, 10 days of age), one pig group (designated as the vaccinated/challenged group) received a single, 1.0 ml dose of bivalent vaccine. Pigs in both the vaccinated/challenged and unvaccinated/challenged groups were then inoculated intranasally with PCV2b and M. hyopneumoniae at 0 dpc (35 days of age). Pigs in vaccinated/challenged group induced significantly higher levels of neutralizing antibodies against PCV2b and cell-mediated immunity against PCV2b and M. hyopneumonia when compared with pigs in unvaccinated/challenged group. The vaccination of pigs with a bivalent vaccine also reduced PCV2b viremia, reduced mycoplasmal nasal shedding, and decreased the severity of both lung and lymphoid lesions for PCV2b and M. hyopneumoniae infection, respectively. The results of this study demonstrated that the evaluated bivalent vaccine was effective in protecting pigs against PCV2b and M. hyopneumoniae infection.

Experimental efficacy of a trivalent vaccine containing porcine circovirus types 2a/b (PCV2a/b) and Mycoplasma hyopneumoniae against PCV2d and M. hyopneumoniae challenges.

The purpose of this experimental study was to evaluate the efficacy of a new trivalent vaccine containing porcine circovirus types 2a/b (PCV2a/b) and Mycoplasma hyopneumoniae. Pigs were administered the vaccine intramuscularly as either at 3 and 24 days of age with 1.0 mL or at 21 days of age with 2.0 mL according to the manufacturer's recommendations. The pigs were challenged at 42 days of age with either PCV2d (intranasal route) or M. hyopneumoniae (intratracheal route), or both. No statistical differences were observed between the one-dose and two-dose experiments based on clinical (growth performance), immunological (protective immunity), microbiological (viremia and laryngeal swab), and pathological (pulmonary and lymphoid lesion) outcomes. Pigs in vaccinated/challenged and unvaccinated/unchallenged groups showed significant difference in growth performance compared to pigs in the unvaccinated/challenged group in both dosage experiments. Vaccinated pigs elicited a significant amount of protective immunity for PCV2d-specific neutralizing antibodies and interferon-γ secreting cells (IFN-γ-SC) as well as M. hyopneumoniae-specific IFN-γ-SC significantly post-challenge compared to unvaccinated/challenged pigs. Vaccination and challenge reduced the viral load amount of PCV2d in the blood and reduced the M. hyopneumoniae load in laryngeal swab, while simultaneously reducing both pulmonary and lymphoid lesion severity when compared to unvaccinated/challenged pigs. Trivalent vaccination provided good protection against a single PCV2d challenge, single M. hyopneumoniae challenge, and a PCV2d/M. hyopneumoniae dual challenge.

A Comparison of Pathogenicity and Virulence of Three Porcine Circovirus Type 2 (PCV2) Genotypes (a, b, and d) in Pigs Singularly Inoculated with PCV2 and Dually Inoculated with Mycoplasma hyopneumoniae and PCV2.

The objective of this study was to compare the virulence of three different porcine circovirus type 2 (PCV2) genotypes (PCV2a, PCV2b, and PCV2d) in pigs infected with either one of these three PCV2 genotypes versus pigs dually inoculated with Mycoplasma hyopneumoniae and PCV2. Pigs were inoculated intratracheally with M. hyopneumoniae at 4 weeks of age followed by another intranasal inoculation at 6 weeks of age with one of three PCV2 genotypes. Dual infection with two pathogens produced moderate and severe dyspnea, lethargy, and reduced weight gain in pigs regardless of the PCV2 genotype evaluated compared with pigs only inoculated with PCV2. The overall levels of PCV2d viremia and severity of lymphoid lesions, and PCV2-antigen within lymphoid lesions were significantly higher in pigs dually inoculated with M. hyopneumoniae/PCV2d when compared with all other dually inoculated groups. The level of PCV2 viremia and the production of PCV2-associated lymphoid lesions did not differ significantly among PCV2a, PCV2b, and PCV2d single-inoculated pig groups. The results of this study demonstrated that M. hyopneumoniae potentiated the replication of PCV2d more than it did with the other PCV2 genotypes as measured by lymphoid lesion severity.

Pathogenicity of Porcine Circovirus Type 2d (PCV2d) in Pigs Infected with PCV2d or Co-infected with Mycoplasma hyopneumoniae and PCV2d or with Porcine Reproductive and Respiratory Syndrome Virus and PCV2d.

The objective of this study was to determine the pathogenicity of porcine circovirus type 2d (PCV2d) in pigs inoculated intranasally with PCV2d alone, PCV2d in combination with Mycoplasma hyopneumoniae or PCV2d in combination with porcine reproductive and respiratory syndrome virus (PRRSV). Pigs infected with PCV2d alone were asymptomatic. All pigs inoculated with either M. hyopneumoniae and PCV2d or with PCV2d and PRRSV developed porcine circovirus-associated disease (PCVAD), as characterized by a sudden onset of clinical signs and disseminated granulomatous inflammation. Inflammation was mainly present in lymph nodes and spleen, and occasionally in liver and kidney. Pigs in both of these dually infected groups also had significantly higher (P <0.05) microscopic lymphoid lesion scores and a significantly higher (P <0.05) number of PCV2-positive cells in lymph node tissue than did pigs inoculated with PCV2d alone. The M. hyopneumoniae and PRRSV combination potentiated the PCV2d load in the blood. Co-infection with PRRSV and PCV2d resulted in a significantly higher blood load of PCV2d compared with the M. hyopneumoniae and PCV2d combination. Successful reproduction of PCVAD in pigs appears to require PCV2d with at least one additional infectious agent, such as M. hyopneumoniae or PRRSV, for the full manifestation of disease.

Field evaluation of a sing-dose bivalent vaccine of porcine circovirus type 2b and Mycoplasma hyopneumoniae.

BACKGROUND: The field efficacy of a bivalent vaccine containing porcine circovirus type 2b (PCV2b) and Mycoplasma hyopneumoniae was evaluated on three pig farms. METHODS: Three pig farms were used, two of which had a history of subclinical PCV2 and clinical M. hyopneumoniae infections between 84 and 126 days of age while concurrent porcine circovirus-associated disease and clinical M. hyopneumoniae infection between 70 and 105 days of age. Each farm vaccinated pigs with a single dose of a bivalent vaccine at 10 days of age while unvaccinated pigs were administered a single dose of phosphate buffered-saline at the same age. RESULTS: Vaccination improved growth performance and reduced clinical scores significantly (p < .05) when compared with unvaccinated animals. The amount of PCV2d loads in blood and M. hyopneumoniae loads in nasal swabs of vaccinated animals were also significantly lower (p < .05) when compared with unvaccinated animals. Immunologically, vaccinated groups elicited a significantly higher (p < .05) level of protective immunity against PCV2d such as neutralizing antibodies and interferon-γ secreting cells (IFN-γ-SC), as well as protective immunity against M. hyopneumoniae such as IFN-γ-SC when compared with unvaccinated animals. Pathologically, vaccination significantly lowered (p < .05) the scores of M. hyopneumoniae-induced pneumonia and PCV2-associated lymphoid lesions when compared with unvaccinated animals. CONCLUSIONS: The evaluated bivalent vaccine provided good protection against PCV2d and M. hyopneumoniae infection under field conditions.

Comparative Evaluation of Growth Performance between Bivalent and Trivalent Vaccines Containing Porcine Circovirus Type 2 (PCV2) and Mycoplasma hyopneumoniae in a Herd with Subclinical PCV2d Infection and Enzootic Pneumonia.

The present field trial compared two combined vaccines of porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae, each administered in herd with subclinical PCV2d infection and enzootic pneumonia. One vaccine was a bivalent containing PCV2a and M. hyopneumoniae and the other was a trivalent vaccine containing PCV2a and 2b (PCV2a/b), and M. hyopneumoniae. The defining difference between these two vaccines was the inclusion or absence of PCV2b antigen. A total of 480, 21day-old pigs were randomly allocated to one of four treatment groups (120 pigs per group, male = 60 and female = 60). These groups included; one-dose trivalent-vaccinated, two-dose trivalent-vaccinated, one-dose bivalent-vaccinated, and unvaccinated. The one- and two-dose trivalent vaccinated pigs exhibited significantly better growth performance when compared with those vaccinated with the bivalent vaccine. The one- and two-dose trivalent vaccinated pigs also reduced the amount of PCV2d loads in the blood and feces, and resulted in a lower M. hyopneumoniae load in the larynx when compared with one-dose bivalent vaccinated pigs. Statistical differences were not observed between the one- and two-dose trivalent-vaccinated groups in terms of growth performance, serology, amount of PCV2d loads in the blood and feces, amount of M. hyopneumoniae load in larynx, and pathological lesions. The results of the present study will provide swine practitioners and producer with comparative clinical field data to select the proper vaccine and vaccination regiment for herds suffering from subclinical PCV2d infection and enzootic pneumonia.