Distribution of a novel infectious agent in healthy and diseased bicolor damselfish in Florida and the Caribbean

The disease damselfish neurofibromatosis (DNF) affects bicolor damselfish ( Stegastes partitus) on reefs in Florida. This disease consists of periphera l nerve sheath and pigment cell tumors that are eventually fatal. The devel opment of DNF is correlated with the appearance of unusual, extrachromosoma l DNAs in affected fish that appear to be the genome of an undescribed, vir us-like agent. Probes derived from these sequences were used to determine t he distribution of this agent in diseased and healthy fish from several ree fs in South Florida and from selected locations elsewhere in the range of t his species. These analyses demonstrated that naturally diseased fish exhib ited high levels of these DNAs in tumors and, to a lesser extent, in unaffe cted tissues. Fish with experimentally induced DNF exhibited similar levels of this DNA. Healthy adult fish had either no detectable levels of this DN A or very low levels, depending on the sensitivity of the detection techniq ue used. Healthy adults from high disease prevalence reefs were more likely to test positive for this DNA than those from low disease reefs. Juvenile damselfish never contained detectable levels of this agent. Very low levels of this DNA were also detected in healthy fish from the Caribbean and the Bahamas. Dose-response experiments using tumor-derived cell lines indicated that tumor development was directly related to exposure dosages and that v ery low concentrations of this material did not yield tumor development. Ta ken together, these data indicate that high levels of this agent were corre lated with the appearance of this disease and the very low levels often obs erved in healthy fish were not a predictor of tumor development.