Histopathological study of lymphocystis disease virus (LCDV) in cultured false clownfish, Amphiprion ocellaris (Cuvier, 1830) and true clownfish, Amphiprion percula (Lacepede, 1802)

Objective: To study the lymphocystis disease virus (LCDV) in two species of marine ornamental fishes through histopathological investigation along with control for differentiating the tissue damage. Methods: Six naturally infected fishes were collected. They were anaesthetized and subsequently killed by organ dissection. The infected fish organs were aseptically cut off and stored with 10% formalin solution for histological study. Samples were examined for gross pathology including location, distribution, shape, size, colour, consistency and special features of typical external lesions by standard method. Results: The diameter of the tumor nodules ranged from 1 to 2 mm (Amphiprion ocellaris) and 2.5 to 3.5 mm (Amphiprion percula). Light microscopic observation showed over growth of tumor like nodules on the skin or scales and ventral side as well. Numerous hypertrophied cells with basophilic intracytoplasmic inclusion bodies were in the connective tissues of dermis and between scales on two species. The nucleus of lymphocystis cell were enlarged, irregular and containing basophilic marginated chromatin. Thus, the similarities among cellular patterns of different fish LCDV isolates from different hosts indicated that these profiles do not depend on the host species. Conclusions: In conclusion, this current study of histopathological statement of LCDV may be adequate for a presumptive diagnosis of lymphocystis disease from both marine as well as fresh water fish species. The findings of asymptomatic carriers by histology using infected skin and fin sampling, which does not imply animal killing, could be important tool to epizootics caused by LCDV. This study may be very useful for further molecular studies.