Histopathology of “hole-in-the-head” disease in the Nile Tilapia, Oreochromis niloticus

The gross morphology and histopathology of lesions formed in “hole-in-the-head” disease, commonly found in cichlids, is described in the Nile Tilapia, Oreochromis niloticus. The most severe lesions, which in some fish extended into the lateral line canals, were found posterior to the eye. In histological sections of this region in fish without lesions, we found previously unreported small canals running parallel to the epidermis, opening at the …