Confirmation of Mycoplasma hyopneumoniae in a breeding herd through tracheobronchial swab sampling and PCR

Seasonal Variation in Prevalence of Mycoplasma hyopneumoniae and Other Respiratory Pathogens in Peri-Weaned, Post-Weaned, and Fattening Pigs with Clinical Signs of Respiratory Diseases in Belgian and Dutch Pig Herds, Using a Tracheobronchial Swab Sampling Technique, and Their Associations with Local Weather Conditions

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.

Dynamics and chronology of Mycoplasma hyopneumoniae strain 232 infection in experimentally inoculated swine

Direct detection of Mycoplasma hyopneumoniae through molecular tools is a growing trend for early diagnosis, highlighting the importance of knowing M. hyopneumoniae dynamics in the respiratory tract upon infection. This study focused on monitoring the infection level and its effects in different anatomic sites of the respiratory tract of experimentally infected swine in four time-points post-infection. To this end, 24 pigs were allocated to either non-inoculated group (n = 8) or inoculated group (n = 16). On day 0 post-infection (dpi), animals of the inoculated group were intratracheally inoculated with M. hyopneumoniae. Nasal swabs were collected weekly for qPCR detection of bacterial shedding. At 14, 28, 42, and 56 dpi, four animals from the inoculated group and two from the control group were necropsied. Bronchoalveolar lavage fluid (BALF) and samples from three different anatomical tracheal sections (cranial - CT, medium - MT, lower - LT) were collected for qPCR and histopathology. Bacterial loads (qPCR) in tracheal samples were: 4.47 × 10² copies∕μL (CT), 1.5 × 10⁴- copies∕ μL (MT) and 1.4 × 10⁴ copies∕μL (LT samples). M. hyopneumoniae quantification in BALF showed the highest load at 28 dpi (2.0 × 10⁶ copies∕ μL). Microscopic lesions in LT samples presented the highest scores at 56 dpi and were significantly correlated with the pathogen load on 14 dpi (0.93) and 28 dpi (0.75). The greatest bacterial load of M. hyopneumoniae in CT samples and BALF was registered at 28 dpi, and it remained high in BALF and LT throughout the 56 dpi. The pathogen was able to persist during the whole experimental period, however higher estimated quantification values were registered in the lower parts of the respiratory tract, especially at 56 dpi. These findings are important for improving diagnostics, treatment, and control measures of M. hyopneumoniae infection in swine herds.

Detection of Mycoplasma hyopneumoniae in nasal and laryngeal swab specimens in endemically infected pig herds

BACKGROUND

Apparently, laryngeal swabs (LS) are more sensitive than nasal swabs (NS) and allow earlier detection of Mycoplasma hyopneumoniae by PCR. However, antecedents about the compared detection of M hyopneumoniae with NS and LS in growing pigs, from naturally infected herds, are lacking in the literature. Thus, this study compared the PCR detection of M hyopneumoniae from NS and LS in pigs of various ages.

METHODS

A longitudinal study was performed at two farms where NS and LS were collected from three consecutive groups of 20 pigs at 3, 6, 10, 16 and 22 weeks of age. All samples were analysed by nested PCR for M hyopneumoniae detection.

RESULTS

The probability of PCR detection of M hyopneumoniae was higher in LS for pigs of all ages (odds ratio (OR)=1.87; 95 per cent confidence interval (CI) 1.31-2.67) and in 22-week-old pigs (OR=4.87; 95 per cent CI 2.86-8.30). The agreement between both sample types was low to moderate (kappa 0.087-0.508), highlighting that M hyopneumoniae does not appear to colonise the respiratory tract in a generalised and consistent fashion.

CONCLUSIONS

The results suggest that LS could be employed at different ages to achieve greater bacterial detection. Considering that LS is a minimally invasive, highly sensitive sample compared with the traditional NS, it could be suggested to employ this sample type for M hyopneumoniae detection in naturally infected pigs.