Lymphocystis disease in Baltic herring (Clupea harengus var. membras L.)

Abstract

Lymphocystis disease has been demonstrated in herring from three different areas of the Baltic Sea. An investigation was made from April 1971‐December 1973 in the fishing grounds near the Askö Laboratory. A total of 2629 herrings from randomly selected samples were examined, 14 of which were found to be affected with lymphocystis disease. The relative incidence of the disease varied from 0–2.7% in different samples, and was higher in 1972 (1%) than in 1971 (less than 0.1%). Of 42 diseased herrings with skin lesions 12 also had lesions in internal organs. The lymphocystis cells were usually single in the skin as well as in internal organs, and had a diameter of 1–2 millimetres. They were histologically similar to lymphocystis cells described from other species. Virions with a mean diameter of 300 nm, morphologically similar to earlier descriptions of lymphocystis virus, were also demonstrated.