Experimental Infections with Streptococcus sp. and Pasteurella piscicida in Jack Mackerel, Trachurus japonicus

Abstract

Susceptibilities of jack mackerel to Streptococcus sp. and Pasteurella piscicida of yellowtail origin were studied in experimentally induced infections, comparing with those of yellowtail. In intraperitoneal injections of Streptococcus, mortalities and epicarditis-development rate in jack mackerel were as high as those of yellowtails. Intraperitoneal injections of Pasteurella also induced high mortalities with histopathological features in jack mackerel as well as yellowtail, but the pathogenicity for jack mackerel was less than that for yellowtail. In both the bacterial challenges by peroral and immersion methods, jack mackerel did not show any specific symptom and clearly differed from yellowtail which showed comparatively high mortalities with development of naturally occurring-like lesions in their viscera.
The present results suggest that jack mackerel is a useful laboratory animal in the screening test of chemotherapeutic agents for controling diseases of yellowtail.