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Published on: December 12, 2025
The isolation and molecular characterization of Mycobacterium avium subsp. paratuberculosis in Shandong province,
Ruichao Yue1, Chunfa Liu1, Paul Barrow2
1State Key Laboratories for Agrobiotechnology, Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Transmissible Spongiform Encephalopathy Laboratory, College of Veterinary Medicine, China Agricultural University, Beijing, 100193 China.
Background:
Mycobacterium avium subspecies paratuberculosis (Map) causes Johne's disease in domestic and wild ruminants. It has been a debate that whether Map can cause Crohn's disease in human. To our knowledge there is no report about molecular characterization of Map in China, although several Map strains have been reported in other country. The objectives of this study was to know the recent prevalence of Johne's disease in dairy farms in Shandong province, and have a better understanding of genotypic distribution of Map in China.
Methods:
Johne's disease was detected from 1038 individuals in 19 dairy farms by ELISA. Map in fecal and milk specimens was identified by Ziehl-Neelsen staining and confirmed using PCR-REA. In addition, frozen sections of ileum and mesenteric lymph nodes from two Map shedding cows were performed to observe the histopathological changes. Next-generation sequencing technology was performed to get whole genome sequences.
Result:
A total of 121 (11.7 %) animals were positive for Map antibody from 1038 sera tested, and 11 (57.9 %) dairy herds were positive for Map antibody. Typically histopathologic changes were observed in mesenteric lymph nodes. We have successfully isolated two Map strains, which both were Map-C. The current genome-wide analysis showed that the genome size of our isolates are respectively 4,750,273 and 4,727,050 bp with a same G + C content of 69.3 %, and the numbers of single nucleotide polymorphisms (SNPs) against Map K-10 are respectively 292 and 296.
Conclusion:
Map is a prevalent pathogen among dairy cattle in China. This study successfully isolated two Map strains from one Chinese dairy herd with signs of diarrhoea, and identified that the two isolates were both Map-C. Furthermore, these isolates were most closely related to Map K-10.
Insights
Mycobacterium avium subspecies paratuberculosis (Map) is prevalent in Chinese dairy cattle, with over 11% of animals testing positive. This study isolated two Map-C strains, providing molecular insights into this Johne's disease pathogen in China.
Area of Science:
- Veterinary Microbiology
- Animal Pathology
- Genomics
Background:
- * Mycobacterium avium subspecies paratuberculosis* (Map) is the causative agent of Johne's disease in ruminants.
- * The potential link between Map and human Crohn's disease remains a subject of debate.
- * Limited molecular characterization data exists for Map strains in China.
Purpose of the Study:
- * To determine the prevalence of Johne's disease in dairy farms in China's Shandong province.
- * To characterize the genotypic distribution of Map in China.
- * To provide molecular data on Map strains isolated in China.
Main Methods:
- * Enzyme-linked immunosorbent assay (ELISA) for Johne's disease detection.
- * Ziehl-Neelsen staining and PCR-Restriction Enzyme Analysis (PCR-REA) for Map identification.
- * Histopathological examination of ileum and mesenteric lymph nodes.
- * Whole genome sequencing using next-generation technology.
Main Results:
- * 11.7% of 1038 animals and 57.9% of 19 herds tested positive for Map antibodies.
- * Typical histopathological changes were observed in mesenteric lymph nodes.
- * Two Map-C strains were successfully isolated and sequenced, showing high similarity to the Map K-10 reference strain.
Conclusions:
- * Map is a significant pathogen in Chinese dairy cattle populations.
- * The isolated Map strains belong to the Map-C genotype.
- * This study provides the first molecular characterization of Map strains in China, closely related to Map K-10.
