Detection of infectious hematopoietic necrosis virus in fish mucus

Infectious hematopoietic necrosis virus (IHNV) was detected in mucus collected from the external surface of naturally infected juvenile and adult salmonids. Virus concentrations ranged from 101.0 to 106.0 plaque forming units (PFU) /ml. Juvenile rainbow trout Oncorhynchus mykiss artificially infected with IHNV by the waterborne route had a 100% prevalence of the virus in mucus and 50% in gill tissues 24 h post-exposure. Mucus examined from individual rainbow trout had increasing IHNV concentrations, 101.5 to 103.9 PFU/ml, from 24 to 84 h postinfection. This suggested IHNV detected in mucus resulted from the normal progression of the disease and the integument may be a site of virus replication and a possible portal of entry.