Mycoplasma hyopneumoniae Surveillance in Pig Populations: Establishing Sampling Guidelines for Detection in Growing Pigs

Abstract

Ante-mortem detection of Mycoplasma hyopneumoniae (MHP) infection in swine production systems has relied on antibody testing, but the availability of tests based on DNA detection and novel diagnostic specimens, e.g., tracheal swabs and oral fluids, have the potential to improve MHP surveillance. A field study was performed over a 14-week period during which ten pigs in one pen at the center of a room with 1,250 six-week-old pigs housed in 46 pens were intratracheally inoculated with MHP. Thereafter, one tracheal sample, four serum samples, and one oral fluid sample, were collected from every pen at two-week intervals. Tracheal and oral fluid samples were tested for MHP DNA and serum samples for MHP antibody. Test results were modeled using a hierarchical Bayesian model based on a latent spatial piecewise exponential survival model to estimate the probability of detection by within-pen prevalence, number of positive pens in the barn, sample allocation, sample size, and specimen over time. Analysis showed that tracheal samples provided the earliest detection, especially at large sample sizes. While serum samples are more commonly collected and cheaper to test, high probability of detection estimates were only obtained 30 days post-exposure at large sample sizes. In all scenarios, probability of detection estimates for oral fluids were significantly lower compared to tracheal and serum samples, within 30 days. Ultimately, the choice of specimen type, sample number, and assay will depend on testing objectives and economics, but the estimates provided herein will assist in the design of MHP surveillance and monitoring programs for different situations.