Table 1.

Scoring system for histopathology of lesions in the distal ileum, ileocecal valve, and mesenteric and ileocecal lymph nodes of cull cows naturally infected with M. avium subsp. paratuberculosis

ParameterbTissueaScoreDescription of histopathological changes
VillusDI, ICV0No abnormality
1Mild blunting of villi
2Moderate blunting and fusion of villi
3Marked blunting and fusion of villi
Cellular infiltrationDI, ICV0No cellular infiltration
1Occasional scattered cellular infiltration
2Moderate cellular infiltration
3Severe and extensive cellular infiltration
GranulomaDI, ICV, MLN, ICLN0No lesion
1Small focal granulomas or scattered giant cells
2Multifocal granulomas in some areas of tissue
3Diffused granulomas in large areas of tissue
No. of AFB* per macrophageDI, ICV, MLN, ICLN0No AFB
1<10 AFB
210 to 50 AFB
3>50 AFB
  • a DI, distal ileum; ICV, ileocecal valve, MLN, mesenteric lymph node; ICLN, ileocecal lymph node.

  • b AFB*, acid-fast bacillus stained with the Ziehl-Neelsen (ZN) method.