Extensive sub-acute mortality amongst koi carp in the Eastern United States prompted field and subsequent laboratory investigations.
Epidemiologic history of the outbreak as well as clinical presentation of affected animals suggested a viral etiology. A herpes virus was observed by EM in
tissues of affected fish, and was subsequently isolated in cell culture. Initial infectivity trials suggest that the isolated herpes virus does cause the same
disease in naïve fish subjected to bath exposure. Primary lesions include disseminated myeloproliferative disease, exocrine pancreatic atrophy, and
meningoencephalitis with intra-nuclear inclusion bodies present in neurons. Attempts to re-isolate the virus from experimentally exposed fish are underway. To our
knowledge, this represents the first report and investigation of a herpes virus associated with extensive mortality in adult carp, with implications for
regulation of shipment and showing of koi carp.
This work was supported in part by a grant from the Associated Koi Clubs of America to the Fish Health Service, University of California,