Table 1.
Definition of the immunohistochemical staining scoring system used in a study of the microbiological and histopathological findings in cases of fatal bovine respiratory disease of feedlot cattle in western Canada
| Immunohistochemical staining score | Definition |
|---|---|
| Mannheimia haemolytica (MH) and Histophilus somni (HS) | |
| 0 | Negative |
| 1+ | Positive staining in foci in some but not all fields on the section (4× objective) |
| 2+ | Positive staining in all fields on the section (4× objective) but < 50% of each field is comprised of tissue that is positively stained for antigen |
| 3+ | Positive staining in all fields on the section (4× objective) and > 50% of each field is comprised of tissue that is positively stained for antigen |
| Mycoplasma bovis (MB) | |
| 0 | Negative |
| 1+ | Fewer than 10 lesions/section and < 50% of the area of fields is comprised of tissue that is positively stained for antigen (small and medium sized foci) |
| 2+ | More than 10 lesions/section but < 50% of the area of the fields are comprised of tissue that is positively stained for antigen (small and medium sized foci) |
| 3+ | More than 10 lesions/section and > 50% of the area of most fields is comprised of tissue that is positively stained for antigen (large sized foci) |
| Parainfluenza-3 virus (PI3V) and Bovine respiratory syncytial virus (BRSV) | |
| 0 | Negative |
| 1+ | Positive staining of an occasional bronchus or alveolus only, not all fields (4× objective) have positive airways or alveoli |
| 2+ | Some positive staining in bronchi or alveoli in all fields (4× objective) |
| 3+ | Majority of bronchi (and some alveoli) in all fields have positive staining |
| Bovine viral diarrhea virus (BVDV) | |
| 0 | Negative |
| 1+ | Occasional vessel has positive staining of tunica media (less than 1 vessel/field at 10× objective) |
| 2+ | Most fields have positive staining of 1 or more vessels (10× objective) |
| 3+ | All fields have positive staining of 1 or more vessels |
| 4+ | Positive staining in epithelial cells, as well as in vessels, in all fields of the section (PI/mucosal disease suspect) |
| Infectious bovine rhinotracheitis virus (IBRV) | |
| 0 | Negative |
| 1+ | Occasional foci of positive staining of epithelial cells (fewer than 1 focus/field at 10× objective) |
| 2+ | Most fields have positive staining of 1 or more foci of epithelial cells (10× objective) |
| 3+ | All fields have positive staining of 1 or more foci of epithelial cells (10× objective) |
| 4+ | Positive staining in epithelial cells that comprise more than 50% of the tissues present in the section |
1. Positive control samples for MH, HS, MB, and BVDV had an immunohistochemical staining score of 2+ for each pathogen
2. Positive control samples used for quality assurance had an immunohistochemical staining score of 3+ for PI3V, BRSV, and IBRV
3. All immunohistochemical staining scores were determined by a single technician