The Israeli Journal of Aquaculture - Bamidgeh 55(4), 2003
The 7th Annual Dan Popper Symposium


Ariel Ronen¹, Ayana Perelberg¹,³ , Julia Abramovitz¹, Marina Hutoran¹, Simon Tinman², Izhak Bejerano², Michael Steinitz¹ and Moshe Kotler¹*

1 Department of Pathology, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel

2 Central Fish Health Laboratory, Nir David 19150, Israel

3 Aquaculture Research Station Dor, Ministry of Agriculture and Rural Development, 30820, Israel


Massive mortality of koi and common carp of the Cyprinus carpio species has been observed in many farms throughout Israel, resulting in severe financial losses. This lethal disease is highly contagious and extremely virulent, but morbidity and mortality are restricted to koi and common carp. The virus propagates and induces severe cytopathic effects five days after infection in fresh carp fin cell cultures, but not in epithelioma papillosum cyprini cells. The virus harvested from the fin cell cultures was inoculated into naive koi and common carp and induced the disease with a mortality rate of 75-85%. Using PCR with authentic primers provided final proof that the isolated virus is indeed the etiological agent causing mortality in both food and ornamental carp.

Electron microscopy revealed viral cores with icosahedron morphology of 100-110 nm resembling those of the herpes virus. However, the genome of the isolated virus is a double-stranded DNA molecule of 250-300 Kbp, larger than that of other known Herpesviridae members. The viral DNA seems highly divergent and bears only small fragments (16-45 bp) homologous to the genomes of several DNA viruses. We suggest, therefore, that the etiological agent of this disease may represent an as yet unclassified virus species endemic to carpinoids.

Carps exposed to the virus at 23C for 3-5 days and transferred to the non-permissive temperature of 30C became resistant to the disease and their sera contained a high level of virus specific antibodies. We isolated the attenuated non-pathogenic virus that rendered virus-vaccinated carp resistant to the disease. The vaccinated fish developed high levels of antibodies against the virus. We suggest, therefore, that this attenuated virus could be used as a live vaccine to eradicate this lethal disease that afflicts common and ornamental carp fisheries in many countries.