Goldfish virus going undetected

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Scientists have warned that an emerging viral disease is going undetected in goldfish.

Goldfish Herpes Virus (GHV) or Cyprinid Herpes Virus 2 (CyHV-2) is widespread in the US and is likely to be going undetected worldwide, experts have warned.

Keith Way, Kevin Denham and Keith Jeffrey of CEFAS presented their findings in a paper at the third OATA conference last week.

They claim that CEFAS diagnosed several outbreaks of GHV in 2004 and 2005 and believe that few people are aware of the existence of the disease:

"In 2004 and 2005, CEFAS have diagnosed several goldfish herpes virus outbreaks within the UK. These have been within aquatic centres, fish dealerships and hobbyist collections.

"Recent findings from the USA indicate that CyHV-2 is widespread within the US and likely to be an important, but rarely detected, pathogen of goldfish worldwide."

KHV for goldfishCyprinid Herpes Virus 2 is to goldfish what Koi Herpes Virus (or Cyprinid Herpes Virus 3) is to Common carp.

Both viruses are members of the Herpesviridae family and both viruses are highly contagious.

Like KHV, GHV only shows its symptoms when the water temperature is within a critical range, and like KHV, GHV is believed to be highly host-specific.

The virus can affect all varieties of the goldfish, Carassius auratus, but it is not yet known whether the disease has the potential to spread to our native Crucian carp, Carassius carassius.

GHV was first described from Japan in 1995 following outbreaks in 1992 and 1993, when at the time it was known as Herpesviral Haematopoietic Necrosis Virus (HVHN).

The virus has subsequently been reclassified as CyHV-2 and has since been reported from the USA, Taiwan, Australia and the UK.

SymptomsAffected fish become lethargic, stop eating and develop pale, patchy-looking gill necrosis. Some specimens may also develop small white blister-like pustules on the skin.

Internally, the spleen and kidneys may become pale and swollen and granular lumps and nodules may appear in the spleen.

As with most other fish diseases, the symptoms may differ between outbreaks as bacteria, fungi and parasites may also secondarily infect the fish.

As with KHV, detecting the presence of GHV presents considerable problems.

"There is currently no commercial diagnostic service available", the experts wrote. "Diagnosis relies on a number of techniques. The standard method of isolating viruses by tissue culture is most frequently employed but has been problematical for the diagnosis of goldfish herpesvirus.

"More reliable methods for this virus are the use of PCR (Polymerase Chain Reaction), histological techniques and electron microscope work. CEFAS are currently researching, monitoring and testing for this disease."

Like KHV, fish that recover from the disease may continue to carry the virus and may pass it on to other goldfish.

There are currently no controls on the disease and there is no known treatment.