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 peripheral nerve sheath and pigment cell tumors that are eventually fatal. The development of DNF is correlated with the appearance of unusual, extrachromosomal DNAs in affected fish that appear to be the genome of an undescribed, virus-like agent. Probes derived from these sequences were used to determine the distribution of this agent in diseased and healthy fish from several reefs in South Florida and from selected locations elsewhere in the range of this species. These analyses demonstrated that naturally diseased fish exhibited high levels of these DNAs in tumors and, to a lesser extent, in unaffected tissues. Fish with experimentally induced DNF exhibited similar levels of this DNA. Healthy adult fish had either no detectable levels of this DNA or very low levels, depending on the sensitivity of the detection technique 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 very low concentrations of this material did not yield tumor development. Taken together, these data indicate that high levels of this agent were correlated with the appearance of this disease and the very low levels often observed in healthy fish were not a predictor of tumor development.