Lactococcus garvieae infection of cultured rainbow trout, Oncorhynchus mykiss, in Taiwan and associated biophysical characteristics and histopathology

Abstract

Abstract Five isolates of Gram positive, cocci-shaped, non-hemolytic bacteria were isolated from dis-eased rainbow trout, Oncorhynchus mykiss in Taiwan. The bacteria were identified as Lactococcusgarvieae by physiological, biochemical and 16S rRNA gene sequence analysis . The diseased fishshowed erratic swimming, dark discoloration, and exophthalmia; the mortality varied from 10to 20% in the farms. Histological examination revealed lesions in the brain, heart, spleen, kidney,small intestine and eye. These lesions were characterized by fibroplasia at the serosa of organs.This is the first report of L. garvieae associated with rainbow trout disease in Taiwan. Introduction Streptococcosis has been reported to be asso-ciated with infection of rainbow trout, Oncorhynchus mykiss in Australia, South Af-rica, Israel, Spain, Italy and Japan (Carson etal . 1993; Barrera and Tortucro 1989; Bragg andBrocre 1986; Ceschia et al. 1992; Ghittino andprearo 1992; Hoshina et al . 1958; Kito 1984).The affected fish developed meningitis,meningoencephalitis, and a characteristicacute septicaemia, often with exophthalmos;morbidity was high and mortality was 50%(Eldar