Characterization of Immune Ontogeny of Young Swine to Porcine Circovirus Type 2 Infection

A longitudinal study was conducted to characterize the humoral immune response of pigs to porcine circovirus type 2 (PCV2), the postulated causative agent for postweaning multisystemic wasting syndrome (PMWS). Eight-week-old cesarean-derived, colostrumdeprived (CD/CD) pigs were inoculated with a purified isolate of PCV2 and kept for 35 days post-inoculation (PI). Serum samples were collected from all pigs on day 0 and, thereafter, every 7 days until termination of the study. Naïve young pigs were shown to be susceptible to PCV2. PCV2-specific antibodies were detected by an indirect fluorescent antibody test at day 7 PI and after, whereas neutralizing antibodies were not detected until day 28 PI. Western immunoblot analysis of the sera demonstrated three virus-specific proteins with molecular mass of 28, 28.5 and 35 kD. By comparing the appearance of antibody with protein specificity of antibody response, the 28-kD protein was highly immunogenic and specific for PCV2, suggesting that the 28-kD protein may provide the antigenic basis for the development of diagnostic tests for the detection of PCV2-specific antibody. Other two proteins may be associated with virus neutralization

A Field-Based Assessing the Role of PCV-2 and Other Swine Viruses in Postweaning Multisystemic Wasting Syndrome

A case-control study was conducted to assess the association of major swine viral pathogens, including porcine circovirus type 2 (PCV2) with postweaning multisystemic wasting syndrome (PMWS). Cases were defined as individual pigs with a clinical history of progressive weight loss and respiratory signs and that were subsequently diagnosed with PMWS on the basis of characteristic histopathological lesions. Controls were pigs clinically unaffected and/or from herds in which PMWS had not been diagnosed and with no clinical signs compatible with PMWS. A total of 31 cases and 56 controls were identified from diagnostic submissions or farms within a 6-month period. Among viruses examined, PCV2 appeared to be the most strongly associated with PMWS (P\u3c.05). Risk for PWMS was much higher if animal was coinfected with porcine reproductive and respiratory syndrome virus (odd ratio =31.2). However, PCV2 was found in 62.5% of the control animals and was not detected in 2 of the 31 PMWS pigs. Furthermore, no significant genetic difference was observed among PCV2 isolates from PMWS and clinically normal pigs. The role of PCV2 in PMWS remains to be reassessed

Persistence of PRRSV in Nursery Pigs

Porcine Reproductive and Respiratory Syndrome virus (PRRS)V is known to cause persistent infections in swine populations. We inoculated three week-old feeder pigs with PRRSV (ATCC VR-2332) then collected and analyzed biological samples to determine the pigs’ infection status over time post-inoculation (PI). Infectious virus was detected in 100% of animals at 63 days post inoculation and 90% of animals were still carrying infectious virus at 105 days PI

Porcine circovirus type 2 (PCV2)-infection and re-inoculation with homologous or heterologous strains: virological, serological, pathological and clinical effects in growing pigs.

Long-term PCV2 infection and/or concurrent infection with genotypes PCV2a and PCV2b may play a role in the development of clinical porcine circovirus-associated disease (PCVAD). To evaluate this premise, 24 11-week-old specific pathogen-free (SPF) pigs were randomly assigned to 1 of 4 treatments: negative controls, a single inoculation with PCV2a, single inoculation followed by re-inoculation with a homologous PCV2a strain, or repeated inoculations with heterologous strains (PCV2a, PCV2b). Pigs were evaluated for clinical signs daily through 140 days post inoculation (dpi). Serum samples were collected every other day from dpi 0 through 14 and weekly thereafter. PCV2-inoculated pigs were viremic by dpi 2 and 13 of 18 pigs remained viremic at 140 dpi. No statistical differences in the onset, level, or duration of PCV2 viremia were detected among treatment groups. Anti-PCV2 antibodies were detected between 14 and 28 dpi and were present through 140 dpi without statistical differences in antibody response among treatment groups. In the current study, pigs had extended viremia combined with detectable tissue PCV2 antigen levels despite the presence of high levels of anti-PCV2 antibody; however, no clinical disease was observed

Characterization of Immune Ontogeny of Young Swine to Porcine Circovirus Type 2 Infection

A longitudinal study was conducted to characterize the humoral immune response of pigs to porcine circovirus type 2 (PCV2), the postulated causative agent for postweaning multisystemic wasting syndrome (PMWS). Eight-week-old cesarean-derived, colostrumdeprived (CD/CD) pigs were inoculated with a purified isolate of PCV2 and kept for 35 days post-inoculation (PI). Serum samples were collected from all pigs on day 0 and, thereafter, every 7 days until termination of the study. Naïve young pigs were shown to be susceptible to PCV2. PCV2-specific antibodies were detected by an indirect fluorescent antibody test at day 7 PI and after, whereas neutralizing antibodies were not detected until day 28 PI. Western immunoblot analysis of the sera demonstrated three virus-specific proteins with molecular mass of 28, 28.5 and 35 kD. By comparing the appearance of antibody with protein specificity of antibody response, the 28-kD protein was highly immunogenic and specific for PCV2, suggesting that the 28-kD protein may provide the antigenic basis for the development of diagnostic tests for the detection of PCV2-specific antibody. Other two proteins may be associated with virus neutralization.</p

A Field-Based Assessing the Role of PCV-2 and Other Swine Viruses in Postweaning Multisystemic Wasting Syndrome

A case-control study was conducted to assess the association of major swine viral pathogens, including porcine circovirus type 2 (PCV2) with postweaning multisystemic wasting syndrome (PMWS). Cases were defined as individual pigs with a clinical history of progressive weight loss and respiratory signs and that were subsequently diagnosed with PMWS on the basis of characteristic histopathological lesions. Controls were pigs clinically unaffected and/or from herds in which PMWS had not been diagnosed and with no clinical signs compatible with PMWS. A total of 31 cases and 56 controls were identified from diagnostic submissions or farms within a 6-month period. Among viruses examined, PCV2 appeared to be the most strongly associated with PMWS (P<.05). Risk for PWMS was much higher if animal was coinfected with porcine reproductive and respiratory syndrome virus (odd ratio =31.2). However, PCV2 was found in 62.5% of the control animals and was not detected in 2 of the 31 PMWS pigs. Furthermore, no significant genetic difference was observed among PCV2 isolates from PMWS and clinically normal pigs. The role of PCV2 in PMWS remains to be reassessed.</p

Persistence of PRRSV in Nursery Pigs

Porcine Reproductive and Respiratory Syndrome virus (PRRS)V is known to cause persistent infections in swine populations. We inoculated three week-old feeder pigs with PRRSV (ATCC VR-2332) then collected and analyzed biological samples to determine the pigs’ infection status over time post-inoculation (PI). Infectious virus was detected in 100% of animals at 63 days post inoculation and 90% of animals were still carrying infectious virus at 105 days PI.</p