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 different PRDC pathogens in pigs using PCR. The objective was to determine prevalence of different PRDC pathogens and their variations during different seasons, including correlations with local weather conditions. A total of 974 pig farms and 22,266 pigs were sampled using TBS over a 5-year period. TBS samples were analyzed using mPCR and results were categorized and analyzed according to the season of sampling and local weather data. In samples of peri-weaned and post-weaned piglets, influenza A virus in swine (IAV-S), porcine reproductive and respiratory syndrome virus—European strain (PRRSV1), and M. hyopneumoniae were found as predominant pathogens. In fattening pigs, M. hyopneumoniae, porcine circovirus type 2 (PCV-2) and PRRSV1 were predominant pathogens. Pathogen prevalence in post-weaned and finishing pigs was highest during winter, except for IAV-S and A. pleuropneumoniae, which were more prevalent during autumn. Associations between prevalence of several PRDC pathogens, i.e., M. hyopneumoniae, PCV-2 and PRRSV, and specific weather conditions could be demonstrated. In conclusion, the present study showed that many respiratory pathogens are present during the peri-weaning, post-weaning, and fattening periods, which may complicate the clinical picture of respiratory diseases. Interactions between PRDC pathogens and local weather conditions over the 5-year study period were demonstrated.
Highlights
Porcine respiratory disease complex (PRDC) is a multifactorial and complex disease in nursery and growing pigs [1], provoked by a combination of several infectious viral and bacterial pathogens, environmental stressors, differences in production systems, and management practices [2,3,4]
Multiple agents were reported to be associated with PRDC, including the major pathogens porcine reproductive and respiratory syndrome virus (PRRSV), Mycoplasma hyopneumoniae (M. hyopneumoniae), influenza A virus in swine (IAV-S), and porcine circovirus type 2 (PCV-2) [5,6]
The most commonly identified pathogens are PRRSV, IAV-S, PCV-2, and M. hyopneumoniae, besides other pathogens associated with PRDC, such as Streptococcus suis, A. pleuropneumoniae, P. multocida, DNTpositive P. multocida, Glaeserella parasuis (G. parasuis), Mycoplasma hyorhinis (M. hyorhinis), Mycoplasma hyosynoviae, porcine respiratory coronavirus (PRCV), and porcine cytomegalovirus (PCMV) [3,23,48]
Summary
Porcine respiratory disease complex (PRDC) is a multifactorial and complex disease in nursery and growing pigs [1], provoked by a combination of several infectious viral and bacterial pathogens, environmental stressors, differences in production systems, and management practices [2,3,4]. Mycoplasma hyopneumoniae plays a major role within PRDC as the etiological agent of enzootic pneumonia, a chronic respiratory disease that mainly affects finishing pigs [7,8]. Mycoplasma infections are related to a chronic, non-productive cough This results in economic losses due to reduced growth rate, poorer feed conversion, increased medication use and a higher susceptibility to secondary pathogens, such as Pasteurella multocida (P. multocida) and A. pleuropneumoniae [7]. PCVAD is characterized by lymphoid depletion, which is considered the hallmark lesion [31] This is thought to induce immunosuppression or immunomodulation in the host [32], leading to secondary infections with other viral or bacterial pathogens [33,34,35]. Animals may be carriers of A. pleuropneumoniae at the level of the tonsils and in chronic lung lesions
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