Distribution of Mycobacterium avium subsp. paratuberculosis of dairy cows in Taiwan

• Main Authors: Jin-Ho Guo, 郭晉禾
• Other Authors: Chao-Fu Chang
• Format: Others
• Language: en_US
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/59080167436124154450

碩士 === 國立臺灣大學 === 獸醫學研究所 === 89 === Paratuberculosis also known as Johne’s disease is a chronic infectious disease of the bovine species as well as other ruminant species caused by Mycobacterium avium subsp. paratuberculosis ( Mpt ). The course of this disease is very long and infected animals show no obvious signs at the beginning but proceed into intermittent diarrhea at the end-stage of the disease. Infected cows experience a decrease in milk production which causes great economic losses to diary farmers. Mpt has been suspected to be the pathogen of the human Crohn’s disease, and has caused considerable public health attention. In order to understand the distribution of Mpt in Taiwan, this study was designed to carry out a systematic investigation on the Formosan island using cluster sampling method. A total of 1000 fecal samples from 170 diary farms in 4 different areas of the island ( namely Northern, Eastern, Southern and Central Taiwan ) were collected for isolation of Mpt in Herrold’s egg yolk medium and its identification by PCR as well as DNA probe hybridization method. Eighteen strains of Mpt were isolated from 12 diary farms, giving a positive rate of 7.1 % ( 12/170 ) among diary farms and 1.8 % among dairy cattle ( 18/1000 ). In addition, 2 kinds of ELISA kits were used in a recurrent study of the positive farms’ cattle. Blood samples were taken for Mpt antibody detection. If the result of fecal culture was used as the diagnostic criterion, the sensitivity was 66.7% ( 12/18 ) and specificity 84.3 % ( 54/64 ) for the IDEXX® kit, whereas the sensitivity was 55.5% ( 10/18 ) and specificity 75.0% ( 48/64 ) for the CSL® kit. There were no statistical differences between these 2 ELISA tests and the fecal culture method. In order to understand the differences among the different isolates of Mpt. RAPD and RFLP patterns of 10 different field isolates and one reference strain were compared. Five different RAPD patterns were obtained with the OPE-20 primer using RCR; whereas RFLP analysis resulted in 4 different RFLP patterns after being cleaved by restriction enzyme BstEII. According to the RAPD pattern, Mpt isolates from the same sampling area was not divergent, whereas it was similarity with the RFLP pattern.