Laboratory challenge of Pacific herring Clupea pallasii to Vibrio anguillarum and V. ordallii

Controlled waterborne exposures of Pacific herring (Clupea pallasii) to Vibrio anguillarum and V. ordalii failed to result in overt signs of disease or mortality from vibriosis. Cumulative mortalities among Vibrio - exposed Pacific herring (3.3 - 5.0 percent) were similar to those of saline-exposed negative controls (10 percent) and significantly less (P less than 0.001) than those of Vibrio - exposed Chinook salmon (60 - 97 percent), a known susceptible species. Gross signs of disease did not occur on any dead or surviving Pacific herring; however, exposed Chinook salmon demonstrated classic gross signs of vibriosis. The results indicate that early reports of presumed vibriosis in Pacific herring during the 1950's were likely misdiagnosed cases of a viral disease, possibly viral hemorrhagic septicemia or viral erythrocytic necrosis, which can cause hemorrhagic lesions superficially resembling those of vibriosis.