Identification and characterization of lymphocystis disease virus (LCDV) from Indian glassy fish (Parambassis ranga Hamilton, 1822) in Iran

Lymphocystis disease (LCD) is a self-limiting viral disease characterized by hypertrophy of fibroblastic cells in connective tissues of fishes. Upon presentation of a clinical case in painted Indian glassy fish (Parambassis ranga) with abundant whitish nodules on skin, fins, and eyes at our clinic in Tehran, Iran, in June 2018, suspected viral etiology was on the top of the differential diagnosis list. Therefore, we proceeded with the analysis to exclude parasitic and bacterial agents, and followed up with identification and characterization of the causative as the lymphocystis disease virus. Direct wet mounts of skin nodules revealed multiple hypertrophic host skin cells. Histopathological examination of the whitish fin and skin nodules revealed hypertrophic cells with thick, smooth, hyaline capsules with irregular nuclei and many inclusion bodies resembling characteristics of the Iridoviridae family and lymphocystis disease virus (LCDV) in particular. Molecular detection (PCR) confirmed presence of LCDV in the external nodules and in the homogenate of the internal organs of the infected fish. Sequence analysis of the MCP gene of the detected virus (IR_LCDV) revealed significant identity (97%) with another LCDV isolate previously reported in Himalayan glassy perchlet (Parambassis baculis) in Korea, and assigned the detected virus to genogroup 5. This is the first report on detection and characterization of LCDV in painted glassy fish in Iran.