| Popis: |
Mycoplasma bovis was first isolated from milk of cows with mastitis in USA. Throughout the years, its significance has also been proved in arthritis, pneumonia, otitis and conjunctivitis in calves. In recent years, M. bovis was frequently isolated from nasal cavities and/or pneumonic lungs of calves in many countries in North America, Europe, and Asia. In our previous work we confirmed that M. bovis is a significant and widespread cause of bovine mastitis in Croatia, however there are no data about its role in respiratory diseases of calves. The aim of this study was to investigate the prevalence of nasal carriage of M. bovis and to confirm its role in pneumonia of calves in Croatia. Four farms on which calves from various sources were raised and had continuous problems with chronic pneumonia were selected for the study. M. bovis was suspected as a cause of pneumonia because there were no improvements after prolonged antibiotic therapy. Sixty six nasal swabs and 9 lung samples of calves from 4 farms were obtained and investigated for the presence of M. bovis using enrichment and capture ELISA, culture in Hayflick broth and culture on mycoplasma agar. 10 nasal swabs and all lung samples were also plated on Columbia agar with 5% sheep blood (Biorad, France) for routine bacteriological analysis. After isolation on solid agar and identification by ELISA, 20 isolates were randomly selected and tested by polymerase chain reaction specific. M. bovis was detected in 36 out of 66 (54.5%) nasal swabs and 3 out of 9 (30%) lung samples by enrichment and capture ELISA. All samples positive in ELISA yielded growth of mycoplasma colonies on mycoplasma agar plates. All 20 selected isolates that were previously identified by ELISA were confirmed as M. bovis by PCR. Out of 10 tested nasal swabs, 90% were positive for both M. bovis and Pasteurella multocida. P. multocida and Mannheimia haemolytica only were cultured from one lung sample each, while other 7 samples were negative for bacteria. This work confirmed our assumption that M. bovis is a frequent colonizer of nasal cavities of calves on Croatian farms. M. bovis was isolated for the first time from pneumonic lungs of calves in Croatia thus confirming its role as a cause of pneumonia in calves. However, as there is no routine testing of pneumonic lungs for the presence of mycoplasmas, this problem is often overlooked as more common pathogens such as P. multocida, M. haemolytica and Histophilus somni are more easily isolated and attributed to pathologic conditions. There is an urgent need to stop the spreading of M. bovis by identifying heavily infected herds and establishing prevention and control measures in transport and herd market. |
