Studies on Streptococcus sp. as a Causative agent of an Epizootic among the Cultured Ayu (Plecoglossus altivelis) in Tochigi Prefecture, Japan, 1980

Abstract

From June through October 1980, an epizootic occured among the Ayu (Plecoglossus altivelis) at fresh water farms in Tochigi Prefecture, Japan.
All the diseased fish examined exhibited clinical signs as follows; Externally, numerous petechial hemorrhages in the anal region and ventral body surface, and secretion of abnormal slime on the gill were common. Internally, excessive reddish ascitic fluid accumulation in body cavity and numerous hemorrhages in the intestine were common.
The cultural and biochemical characteristics of five isolates from diseased Ayu as causative organism were quite uniform and resembled those of Streptococcus sp. which ONISHI et al. (1978) and KITAO et al. (1981) reported previously.
The characteristics of all five isolates have been considered to justify classification in genus Streptococcus, and resemble S. pyogenes, S. equisimilis, S. zoopidemicus, S. equi, or S. dysgalactiae especially S. pyogenes mentioned in Bergy's manual 8ed. However, from the isolates exhibited, certain characteristics including serological character served to differentiate them from S. pyogenes.
Under these circumstances it was not possible to classify isolates as members of any the species of genus Streptococcus described previously.