Table 5.

Microscopic lesion grading criteria adopted for scoring tracheal samples of Mycoplasma hyopneumoniae (strain 232) experimentally infected pigs

Score	Lesion description
0	No lesion
1	Epithelium hyperplasia, ciliated cells present in standard quantity with dense cilia
2	Epithelium hyperplasia, reduced cilia density and mild presence of hemorrhage
3	Epithelium hyperplasia with largely reduced cilia density, glandular hyperplasia and increased number of goblet cells
4	Epithelium hyperplasia, glandular hyperplasia, increased number of goblet cells and presence of inflammatory cells infiltration