The objective of this study was to evaluate mutual influence of different pathogens in the development of pneumonia and bronchopneumonia in pigs. Bronchoalveolar lavage fluid of 91 clinically unsuspected and 197 pigs with respiratory problems, were examined. A postmortal examination was done in 128 pigs.
In the analysis, M. hyopneumoniae, M. hyorhinis, PRRSV (US-Type), PRRSV (EU-Type), PCV-2, Influenzavirus Type A, α-hämolytic Streptococcus, β-hämolytic Streptococcus, P. multocida, B. bronchiseptica, H. parasuis and A. pleuropneumoniae, were taken into consideration. The pathological-anatomical examination was evaluated with the prospect of the existence of an interstitial, catarrhal-purulent bronchopneumonia and pleuritis. All examined pathogens were found more often in the clinically suspected animals than in the group of clinically unsuspected animals. This difference was significant for α-hämolytic Streptococcus, H. parasuis, M. hyopneumoniae and M. hyorhinis. PCV-2 and α-hämolytic Streptococcus were isolated most frequently in BAL. The pathogen A. pleuropneumoniae was isolated culturally in two cases from BALF.
A comparison of detection frequency in different weight groups showed that M. hyopneumoniae, M. hyorhinis, P. multocida and B. bronchiseptica occurred more often in heavier, older animals. H. parasuis occurred most frequently in animals with a body weight of ≤ 7,5 kg.
Causal agent associations could be ascertained more frequently in the group of clinically suspected animals than in the group of clinically unsuspected pigs. Remarkably noticeable was that both α-hämolytic Streptococcus as well as M. hyopneumoniae were associated with M. hyorhinis, PRRSV (EU-Type), P. multocida and B. bronchiseptica. These pathogens seemed to favour infections with the above mentioned four causal agents, or that α-hämolytic Streptococcus occurs more when pigs are infection with other pathogens.
P. multocida and B. bronchiseptica were both associated significantly with M. hyopneumoniae, α-hämolytic Streptococcus, PRRSV (EU-Type) and PRRSV (US-Type) respectively. Furthermore a correlation of clinical and pathological examinations scores could be seen for M. hyopneumoniae and α-hämolytic Streptococcus. These two agents were isolated more frequently and semi quantitatively more often in BALF, with increasing severity of clinical and pathological-anatomical changes.
The importance of multiple infections with different causal agents for the disease picture of pneumonia and bronchopneumonia was analysed. A multiple infection with five or more agents was detected significantly more often in the group of clinically suspected animals than in the group of unsuspected pigs. The number of animals, where two or less than two pathogens were detected in the BALF, was significantly higher in the group of clinically unsuspected pigs than in the group of clinically suspected pigs.
The higher the clinical examination score was, the higher were the number of animals, where 5 or more different pathogens could be detected. A similar connection could be seen in the pathological-anatomical examination score.
The more different agents were isolated in BALF in one animal, the higher was the average pathological-anatomical examination score. The results of the analysis in weight groups, showed that with an increase in weight, the number of animals with ≥ 5 and ≤ 2 different agents increased.
This could be due to the different husbandry systems which could cause an infection with various pathogens. Infections with different pathogens are more likely in exploratations with continuous occupation of animals from different origins. A multiple infection is more unlikely in closed exploratations.
BAL can be seen as suitable to diagnose pneumonia or bronchopneumonia in pigs. A cultural and molecular biological evaluation of several samples should be done to enable the initiation of suitable prophylactic and therapeutic measures. A serological examination is given pr