EPIZOOTIC PAPILLOMAS IN BROWN BULLHEADS ICTALURUS-NEBULOSUS FROM SILVER STREAM RESERVOIR, NEW-YORK

Fish from Silver Stream reservoir in Newburgh, New York (USA) were examined in 1985 and 1986 following reports by fishermen who had found a high prevalence of skin lesions in brown bullheads Ictalurus nebulosus caught in the reservoir. Oral and skin papillomas were found in 43.2% and 60.0 % of the brown bullheads from these respective samplings, whereas no papillomas were found in yellow bullheads I. natalis. No viral particles could be identified by electron microscopy in the lesions nor were cytopathic effects observed in primary cell cultures of tumor cells or from cocultivation of these cells with an established brown bullhead cell line. Extracts of the sediment from the reservoir contained known promutagens but the concentrations of these compounds were low and similar to those found at reference sites considered to be non-contaminated. Nevertheless a positive response in the Ames assay of the extracts of the sediment was recorded. Elevated levels of chromium, copper, manganese, lead and vanadium were found in the sediments and copper, manganese, nickel, strontium and lead were elevated in the water. The pH of the interstitial water was 4.5. It is unlikely that any of these parameters was the sole causative factor in the etiology of the papillomas.