Jeremy Kroll

Proliferative enteropathy: a global enteric disease of pigs caused by Lawsonia intracellularis.

Abstract Proliferative enteropathy (PE; ileitis) is a common intestinal disease affecting susceptible pigs raised under various management systems around the world. Major developments in the understanding of PE and its causative agent, Lawsonia intracellularis, have occurred that have led to advances in the detection of this disease and methods to control and prevent it. Diagnostic tools that have improved overall detection and early onset of PE in pigs include various serological and molecular-based assays. Histological tests such as immunohistochemistry continue to be the gold standard in confirming Lawsonia-specific lesions in pigs post mortem. Despite extreme difficulties in isolating L. intracellularis, innovations in the cultivation and the development of pure culture challenge models, have opened doors to better characterization of the pathogenesis of PE through in vivo and in vitro L. intracellularis–host interactions. Advancements in molecular research such as the genetic sequencing of the entire Lawsonia genome have provided ways to identify various immunogens, metabolic pathways and methods for understanding the epidemiology of this organism. The determinations of immunological responsiveness in pigs to virulent and attenuated isolates of L. intracellularis and identification of various immunogens have led to progress in vaccine development.

Carbopol improves the early cellular immune responses induced by the modified-life vaccine Ingelvac PRRS® MLV.

Adjuvants enhance both the magnitude and duration of immune responses, therefore representing a central component of vaccines. The nature of the adjuvant can determine the particular type of immune response, which may be skewed toward cytotoxic T cell (CTL) responses, antibody responses, or particular classes of T helper (Th) responses and antibody isotypes. Traditionally, adjuvants have been added to intrinsically poor immunogenic vaccines, such as those using whole killed organisms or subunit vaccines. Here, we have compared cellular immune responses induced by the immunogenic modified life-attenuated vaccine Ingelvac PRRS® MLV when administered alone or in combination with carbopol, a widely used adjuvant in veterinary medicine. Using functional readouts (IFN-γ ELISpot and cell proliferation) and analyzing phenotypical hallmarks of CD4T cell differentiation, we show that carbopol improves cellular immunity by inducing early IFN-γ-producing cells and by preferentially driving T cell differentiation to effector phenotypes. Our data suggest that adjuvants may enhance and modulate life-attenuated--not only subunit/inactivated--vaccines.

Development of a real-time polymerase chain reaction assay for detection of Actinobacillus suis in porcine lung

In the current study, the development and validation of a real-time polymerase chain reaction (PCR) assay using a TaqMan-labeled probe for the detection of Actinobacillus suis from porcine lung samples is described. This real-time PCR amplified a 110-bp region of the 23S ribosomal RNA gene from A. suis but not from other bacteria. First, the assay was validated with 183 bacterial strains representing different species of bacteria. Subsequently, 85 porcine lung specimens that were declared A. suis–positive and –negative by bacterial culture and identification were tested to assess whether it can be performed directly on tissue specimens. The bacterial culture results and real-time PCR results agreed across all the samples tested assigning 100% positive and negative predictive values to the PCR. Further, the detection limit of the assay was 380 colony-forming units (CFU) per ml or approximately 1 CFU per reaction. In conclusion, the TaqMan real-time PCR assay described herein is a highly specific, sensitive, and reproducible test, which can be used to detect A. suis DNA in porcine lung specimens, thus providing a timely diagnosis.

Efficacy of an inactivated Mycoplasma hyorhinis vaccine in pigs

Lameness and polyserositis in pigs caused by Mycoplasma hyorhinis are generally treated with antibiotics and may require multiple doses. The costs of these antibiotics combined with economic losses from culling and reduced feed conversion due to lameness are hardships to the swine producer. In this study we have demonstrated efficacy of an inactivated M. hyorhinis vaccine administered to three-week old caesarian-derived colostrum-deprived piglets. Three doses of vaccine (high, medium, and low) were evaluated and compared to a placebo control. Mycoplasma hyorhinis challenge occurred three weeks after vaccination. Pigs were observed for lameness and respiratory distress for three weeks following challenge. Pigs were then euthanized and a gross pathological evaluation for polyserositis and arthritis was performed. A minimum immunizing dose of vaccine was defined as containing at least 7.41 × 107 CCU of M. hyorhinis per 2.0 mL dose as represented by the medium dose vaccine. This vaccine provided significant reductions in lameness and pericarditis with preventive fractions of 0.76 (95% CI [0.26, 0.92]) and 0.58 (95% CI [0.31, 0.74]), respectively, compared to the placebo control group. A significant increase in post-challenge weight gain (P < .0001) was also achieved with this vaccine, with an average daily gain (ADG) of 0.92 lbs/day compared to 0.57 lbs/day in the placebo group.

Initial vaccination and revaccination with Type I PRRS 94881 MLV reduces viral load and infection with porcine reproductive and respiratory syndrome virus

BackgroundPorcine reproductive and respiratory syndrome (PRRS) causes respiratory distress in pigs, reproductive failure in breeding-age gilts and sows, and can have devastating economic consequences in domestic herds. Several PRRS vaccines are available commercially. This study compared the effectiveness of single-vaccination and revaccination schedules using the PRRS 94881 Type I modified live virus (MLV) vaccine ReproCyc® PRRS EU with no vaccination (challenge control) in protecting against a PRRS virus (PRRSV) challenge in non-pregnant gilts.ResultsData were available from 48 gilts across three groups: a challenge control group (n = 16), which received no vaccination; a revaccination group (n = 16), which received ReproCyc® PRRS EU on Days 0 and 56; and a single vaccination group (n = 16), which received ReproCyc® PRRS EU on Day 56. All gilts were PRRSV RNA-negative (based on reverse transcription and quantitative polymerase chain reaction [RT-qPCR]) and PRRSV seronegative (based on enzyme-linked immunosorbent assay [ELISA]) at Day 0. All gilts were challenged with PRRSV strain 190136 on Day 91.Viral RNA loads in both vaccination groups were significantly reduced compared with the challenge control group on Days 98 (P < 0.0001) and 101 (P < 0.0001), indicating that vaccinated gilts were better able to respond to challenge than unvaccinated gilts. At all timepoints following challenge, mean viral RNA load and the percentage of PRRSV RNA-positive gilts were numerically higher in the single-vaccination group than in the revaccination group; these differences were statistically significant on Day 101 (P = 0.0434). Furthermore, viremia levels after challenge were significantly lower in the revaccination group than in the single-vaccination group based on median area under the curve (AUC) values for viral RNA load from Day 91 to Day 112, suggesting that revaccinated gilts had better protection from viral infection than gilts who received a single vaccination. Protection from viremia did not correlate with the proportion of seropositive gilts on Day 91. In the single-vaccination group, 94% of pigs were seropositive on Day 91 compared with 56% in the revaccination group. Vaccination was well tolerated and no safety concerns were identified.ConclusionsBoth single-vaccination and revaccination with ReproCyc® PRRS EU were effective in reducing PRRSV viremia post-challenge. These findings have important implications for herd management as both the single-vaccination and revaccination schedules protect against PRRSV challenge, with revaccination appearing to provide better protection from viremia than single vaccination.

Age susceptibility of caesarian derived colostrum deprived pigs to Mycoplasma hyorhinis challenge

Mycoplasma hyorhinis (MHR) is a major cause of lameness, arthritis, and polyserositis among growing pigs. Reduced performance and culling due to MHR infection result in economic losses in swine production. We have previously developed an MHR challenge model in seven week-old CDCD pigs using cell-associated challenge material which results in both severe pericarditis and lameness. In this study we sequentially challenged CDCD pigs at seven, ten, thirteen, and sixteen weeks of age. Lameness was observed in >60% of the animals in the first three age groups but only 33% in the oldest age group. The number of animals with arthritis declined from 100% at seven weeks, to 56% at ten weeks and approximately 25% at both thirteen and sixteen weeks of age. Pericarditis was observed in 87% of the seven week challenge group, 28% in the ten week challenge group, 8% in the thirteen week challenge group and 4% in the sixteen week challenge group. All challenged groups showed a reduced average daily gain (ADG) compared to their age-matched non-challenged control groups. The largest disparity in ADG (1.2 lbs/day difference) was noted at thirteen weeks of age. Results of this study demonstrate that these animals were susceptible to MHR-associated lameness through sixteen weeks of age while susceptibility to MHR-associated polyserositis appeared to peak at seven weeks of age.