Prevalence and Seasonal Variation of Different Respiratory Pathogens in Post-Weaned Pigs with Signs of Clinical Respiratory Disease Using a Tracheobronchial Swab Sampling Technique: An Update from Belgium and the Netherlands

Abstract

Besides Mycoplasma hyopneumoniae (M. hyopneumoniae), many other viruses and bacteria can concurrently be present in pigs. These pathogens can provoke clinical signs, known as porcine respiratory disease complex (PRDC). A sampling technique on live animals, namely tracheobronchial swab (TBS) sampling, was applied to detect the major PRDC pathogens in pigs using PCR. The objective was to determine prevalence of different PRDC pathogens and their seasonal variations in Belgium and the Netherlands. A total of 600 pig farms and 9,000 post-weaned piglets were sampled using TBS over a 4-year period. TBS samples were analyzed using mPCR and results were categorized and analyzed according to the season of sampling. In Belgium, 53.8% of the sampled farms were PRRSV-positive, followed by M. hyopneumoniae (48.8%) and IAV-S (40.3%), whereas only 20.6% of the farms were detected PCV-2- positive. In the Netherlands, a similar percentage of farms were detected positive for PRRSV (51.4%) and IAV-S (49.1%), whereas a lower percentage of farms was M. hyopneumoniae-positive (32.4%) and only 8.0% was detected PCV-2-positive. Combined infections consisted of M. hyopneumoniae - PRRSV, PRRSV - IAV-S, and M. hyopneumoniae - PRRSV - IAV-S in both countries. In Belgium, the combination of M. hyopneumoniae - PRRSV - PCV-2 also had a relevant prevalence. For all analyzed PRDC pathogens, clear variations among different seasons could be detected. In conclusion, the present study showed that many respiratory pathogens are present during the post-weaning period, which may complicate the clinical picture of respiratory diseases, and their prevalence may vary among seasons.