A histopathological study of streptococcal disease in tilapia.

A histopathological study was made on an infection of Streptococcus sp. in cultured tilapia, Sarotherodon niloticus, which occurred in warm water ponds during the winter of 1980. The external signs were dermal hemorrhage and exophthalmia. The internal signs were dropsy, epicarditis, peritonitis, pale-colored liver, splenomegary and nodule formation in gonads. On histopathological examination, the bacterial dissemination was systemic. Abscesses and granulomas were found to develope in the infected orbital adipose tissue of the exophthalmic eyes. Infiltration of bacteria-laden macrophages and granuloma formation were observed in the infected lesions of the epicardium, capsules of the liver and spleen, peritoneum, stomach, intestine, brain, ovary and testis.