Scientists have replicated the KHV virus in Fathead minnow cells for the first time.
A team of American veterinary scientists successfully isolated the virus from an outbreak in wild common carp and found that it had the ability to infect cultures of Fathead minnow cells under laboratory conditions.
The virus used was associated with a mass mortality event in the wild which killed thousands of Common carp in the Chadakoin River, an outlet stream from Chautuaqua Lake, in western New York State in July 2004.
The symptoms of the disease were similar to those seen in other reported KHV outbreaks, with marked hyperplasia of gill tissues, abdominal lesions and "severe multifocal to diffuse external haemorrhages".
The National Veterinary Services Laboratories in Iowa confirmed the identity of the virus as KHV, or Cyprinid Herpes Virus-3 (CyHV-3) as it is now formally known.
The findings were published recently in the Journal of Wildlife Diseases.
The ability for the virus to replicate well in Fathead minnow (FHM) cell cultures is unusual, as this is typically a trait of Spring Viraemia of Carp (SVC), and not of KHV.
KHV is currently believed to be capable of infecting only Cyprinus carpio, so the news that it can replicate in Fathead minnow cells is intriguing.
Professor Paul Bowser, the lead author of the study, told Practical Fishkeeping that the following year, a much larger mass mortality event caused by KHV hit Chautuaqua Lake and killed an estimated 500,000-750,000 lbs of carp.
He said that in both cases, the virus would grow in Fathead minnow cell cultures for the first two or three passages, but then the cells did not support the growth of the virus.
Bowser did not know whether this was an indication of whether the virus might be able to infect species other than carp: "There has been experimental work showing that KHV has little virulence in goldfish. So I would expect that it would have to make more than a minor change to be able to jump to another species in family Cyprinidae."
For more details see the paper: Grimmett SG, Warg JV, Getchell RG, Johnson DJ and PR Bowser (2006) - An unusual Koi Herpesvirus associated with a mortality event of Common carp, Cyprinus carpio, in New York State, USA. Journal of Wildlife Diseases, 42(3), 2006. pp 658-662.