What are the best diagnostic tools for tracking Mycoplasma hyopneumoniae in swine?

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M. hyopneumoniae causes one of the swine industry’s most devastating diseases—a chronic, infectious pneumonia that can cause respiratory distress and lung lesions in pigs. It can also severely slow pig growth. In order for producers and veterinarians to best measure the success of their disease control and elimination efforts, they need to be able to detect the pathogen in live pigs. However, many diagnostic tools can be unreliable. Dr. Maria Pieters’ lab at the University of Minnesota College of Veterinary Medicine recently led a study to decipher the reliability of two tools, laryngeal swabs and deep tracheal catheters, in detecting the pathogen.

The goal of the study was to provide veterinarians with measurable evidence reflecting which tool to use when tackling M. hyopneumoniae. The team concluded that the deep tracheal catheters were more likely to detect an infection than laryngeal swabs. They did note, however, that the accuracy varied over time and by exposure method, which they recommend veterinarians keep in mind when designing diagnostic strategies. Read more about this study on the Veterinary Microbiology website.

One of the objectives of the MycoLab at the University of Minnesota is to provide producers and veterinarians with strategies for early detection and investigation of Mycoplasma hyopneumoniae infections on the farm. A comprehensive summary table with how-to videos and recommendations for each sample types is freely available on the University website.

Abstract

Detection of Mycoplasma hyopneumoniae infection in live pigs is a critical component to measure the success of disease control or elimination strategies. However, in vivo diagnosis of M. hyopneumoniae is difficult and the imperfect sensitivity of diagnostic tools has been deemed as one of the main challenges. Here, the sensitivity of laryngeal swabs and deep tracheal catheters for detection of M. hyopneumoniae early and late after infection was determined using inoculation status as a gold standard in experimentally infected pigs and a Bayesian approach in naturally infected pigs. Three-hundred and twenty 8-week old seeder pigs were intra-tracheally inoculated with M. hyopneumoniae strain 232 and immediately placed with 1920 contact pigs to achieve a 1:6 seeder-to-contact ratio. A subset of seeders and contacts were longitudinally sampled at 7, 28, 97, and 113 days postinoculation (dpi) and at 28, 56, 84, and 113 days post-exposure (dpe), respectively, using laryngeal swabs and deep tracheal catheters. Samples were tested for M. hyopneumoniae by a species-specific real-time PCR. The sensitivity of deep tracheal catheters was higher than the one obtained in laryngeal swabs at all samplings (seeders: 36% higher than laryngeal swabs at 7 dpi, 29% higher at 97 dpi, and 44% higher at 113 dpi; contacts: 51% higher at 56 dpe, 42% higher at 84 dpe, and 32% higher at 113 dpe). Our study indicates that deep tracheal catheters were a more sensitive sample than laryngeal swabs. The sensitivity of both sample types varied over time and by exposure method, and these factors should be considered when designing diagnostic strategies.

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