Due to the significance of Mycoplasma hyopneumoniae as a swine respiratory pathogen, acclimation measures are taken into consideration when obtaining replacement gilts from negative sources to be introduced to endemically infected herds. The aim of this study was to evaluate the optimum seeder-to-naïve gilt ratio in a 4-week period for successful natural exposure to M. hyopneumoniae. Sixty gilts were divided in two groups, 21 2-week old seeder gilts were inoculated with M. hyopneumoniae, and 39 aged-matched naïve gilts were exposed to the seeders during a 4-week period. The exposure was set by dividing the gilts into six groups of 10 with different ratios of seeder-to-naïve, from 1:9 until 6 seeders and 4 naïve gilts. Laryngeal swabs, oral fluids and blood samples were collected from all gilts prior to, during and after inoculation and exposure. Infection in seeders was confirmed by development of clinical signs, seroconversion post-inoculation, and detection of M. hyopneumoniae genetic material. Naïve were considered positive after 4 weeks if M. hyopneumoniae was detected on bronchial swab or fixed lung tissue. As result, 33% (3/9) naïve gilts were positive in the 1:9 ratio, 75% (6/8) in 2:8, 28% (2/7) in 3:7, 33% (2/6) in 4:6, 80% (4/5) in 5:5 and 100% (4/4) in the 6:4 ratio. The estimated transmission rate (β) and expected probability of infection (ψ) were 1.28 per pig/week and 0.6, respectively. In this study, six seeders were required in a group of 10 gilts for successful exposure to M. hyopneumoniae in a 4-week exposure period.
Bibliographical noteFunding Information:
The authors thank Dr. Samuel Baidoo for help with gilt acquisition. Dr. Darin Madson for shared knowledge and technical support with lung tissue evaluation. Dr. Kim VanderWaal for assistance on data analysis. Special thanks to Cesar Prado and Lucas dos Santos for their help with sample collection; and My Yang and Alyssa Anderson for their help with sample processing and testing. This study was funded by Boehringer Ingelheim Vetmedica Inc. and the Swine Disease Eradication Center (University of Minnesota) .
© 2016 Elsevier B.V.
Copyright 2017 Elsevier B.V., All rights reserved.
- Enzootic pneumonia
- Gilt acclimation
- Seeder-to-naïve exposure model
- Sow farm
- Transmission rate