The first left gill arch of both AGD infected and control fish was
divided into three sites, where transversal sections were cut: dorsal, medial and ventral. The three transversal gill sections were
placed in the same paraffin block and then transferred to the glass
side in a defined order for future reference. The second left gill arch
was sectioned longitudinally for the assessment of AGD severity.
The samples were processed by routine histology.