A comparison of three sampling approaches for detecting PRRSV in suckling piglets.

Determining whether porcine reproductive and respiratory syndrome virus (PRRSV) is circulating within a breeding herd is a longstanding surveillance challenge. Most commonly, piglets in farrowing rooms are sampled to infer the PRRSV status of the sow herd, with sample size based on the expectation of hypergeometric distribution and piglet selection based on simple random sampling (SRS), i.e., randomly selecting individuals from a population in a manner that all individuals have equal chance of being selected. Conceptually straightforward, the assumptions upon which it is based (homogeneous population and independence of individuals) rarely hold in modern swine facilities. Alternative approaches for sample selection include two-stage stratified sampling (2SS), i.e., randomly selecting litters (first stratum) and randomly selecting piglets (second stratum) within selected litters, and risk-based sampling (RBS), i.e., selecting litters with a higher risk of having viremic piglets, and randomly selecting pigs within those litters. The objectives of this study were to 1) characterize the pattern of distribution of PRRSV-viremic piglets in farrowing rooms and 2) compare the efficiency of SRS, 2SS, and RBS for the detection of PRRSV-viremic piglets. In 12 sow farms, serum samples were collected from all 4510 piglets in 422 litters housed in 23 farrowing rooms and tested for PRRSV RNA. At the population level, the distribution of PRRSV-viremic pigs was analyzed for population homogeneity and spatial clustering. At the litter level, litter size and sow parity were evaluated as risk factors. A non-homogeneous distribution of PRRSV-viremic piglets was observed in nearly all farrowing rooms (15/16), and spatial clustering detected on 11 occasions (11/16). Simulated sampling based on farrowing room data determined that 2SS required 1-to-25 fewer samples than SRS to detect ≥ 1 viremic piglet in 13 of 16 rooms and the same number of samples in 3 rooms. RBS required 1-to-7 fewer samples than 2SS to detect ≥ 1 viremic piglet in 7 of 16 rooms, the same number of samples in 6 rooms, and 1 more sample in 3 rooms. Notably, SRS was less efficient than either 2SS or RBS in detecting PRRSV-viremic piglets in farrowing rooms, regardless of the confidence level. It may be concluded that the core assumptions upon which most current surveillance methods are based do not hold in modern farrowing room facilities. Simulation-based sample size tables for SRS and 2SS are provided.

PPARG Post-translational Modifications Regulate Bone Formation and Bone Resorption.

The peroxisome proliferator-activated receptor gamma (PPARγ) regulates osteoblast and osteoclast differentiation, and is the molecular target of thiazolidinediones (TZDs), insulin sensitizers that enhance glucose utilization and adipocyte differentiation. However, clinical use of TZDs has been limited by side effects including a higher risk of fractures and bone loss. Here we demonstrate that the same post-translational modifications at S112 and S273, which influence PPARγ pro-adipocytic and insulin sensitizing activities, also determine PPARγ osteoblastic (pS112) and osteoclastic (pS273) activities. Treatment of either hyperglycemic or normoglycemic animals with SR10171, an inverse agonist that blocks pS273 but not pS112, increased trabecular and cortical bone while normalizing metabolic parameters. Additionally, SR10171 treatment modulated osteocyte, osteoblast, and osteoclast activities, and decreased marrow adiposity. These data demonstrate that regulation of bone mass and energy metabolism shares similar mechanisms suggesting that one pharmacologic agent could be developed to treat both diabetes and metabolic bone disease.

Detection of airborne influenza a virus in experimentally infected pigs with maternally derived antibodies.

This study assessed whether recently weaned piglets with maternally derived antibodies were able to generate infectious influenza aerosols. Three groups of piglets were assembled based on the vaccination status of the dam. Sows were either non-vaccinated (CTRL) or vaccinated with the same (VAC-HOM) strain or a different (VAC-HET) strain to the one used for challenge. Piglets acquired the maternally derived antibodies by directly suckling colostrum from their respective dams. At weaning, pigs were challenged with influenza virus by direct contact with an infected pig (seeder pig) and clinical signs evaluated. Air samples, collected using a liquid cyclonic air collector, and individual nasal swabs were collected daily for 10 days from each group and tested by matrix real-time reverse transcriptase polymerase chain reaction (RRT-PCR) assay. Virus isolation and titration were attempted for air samples on Madin-Darby canine kidney cells. All individual pigs from both VAC-HET and CTRL groups tested positive during the study but only one pig in the VAC-HOM group was positive by nasal swab RRT-PCR. Influenza virus could not be detected or isolated from air samples from the VAC-HOM group. Influenza A virus was isolated from 3.2% and 6.4% air samples from both the VAC-HET and CTRL groups, respectively. Positive RRT-PCR air samples were only detected in VAC-HET and CTRL groups on day 7 post-exposure. Overall, this study provides evidence that recently weaned pigs with maternally derived immunity without obvious clinical signs of influenza infection can generate influenza infectious aerosols which is relevant to the transmission and the ecology of influenza virus in pigs.