Since May 1998 several outbreaks of what has become known as Koi Herpesvirus(KHV) caused mass mortalities in private stocks and fish farms in the northwest of Israel, the mid-Atlantic region of the USA, and in different locations elsewhere in the world, resulting in enormous financial losses for those enterprises concerned. The most recent outbreak in mid-April in East Java, Indonesia caused losses estimated at US$5 million. It will have a negative effect to the region's koi export industry no doubt.

In the May 2002 issue of OFI Journal, John Dawes provides an update on the status of the Koi viral disease in Israel and illuminates it with some of the latest research findings. The message is certainly that there is life after KHV, but more important, the virus may not be a Herpesvirus after all. This bodes well for the industry since the disease may not exhibit the fatal long term characteristics expected of a Herpesvirus.

To summarize the gist of the article: (sometimes verbatim, without permission) The initial 1998 Israeli outbreak was followed by three others within 18 months; each on a different farm. Each of these outbreaks has been contained and overcome within a period of 12-18 months and the output of clean fish generally became possible 12-18 months after completion of the eradication programs. The virus linked with the disease has been accepted as being a Herpesvirus (Hedrick et al, 2000) especially because transmission electron micrographs showed the viral particles exhibit the characteristic Herpesvirus shape when viewed in cross section at high magnitude. However, recent research by Professor Moshe Kotler and colleagues at The Hebrew University and the team led by Dr. Izhak Bejerano at the Israeli Central Fish Health Laboratory, indicates that the virus may be a double-stranded DNA virus with icosahedron morphology that makes it resemble a Herpesvirus. (An icosahedron is a solid body with twenty plane faces, only a few of which can be seen in cross sectional view under transmission electron microscopic examination). This may help explain the results of the various tests, experiments and field trials that have been carried out over the past few years. It may also mean that the periods of latency (dormancy) that are characteristic of Herpesviruses - such as those that cause cold sores in humans - may not apply to the Koi virus. This has significant implications for the rapid restoration of an infected Koi farm to good health. Logically, if the causative agent is not a Herpesvirus, the disease will require renaming, since the KHV label will no longer apply.

The researchers carried out numerous tests on what they termed NIF's (natural immune fish). The main conclusions derived from these tests are that:

1. NIF's do not infect fish which have never been exposed to the virus before, irrespective of whether these are newly-hatched fry, or fish at any other stage of maturity; and
2. NIF's do not appear to be carriers; and
3. NIF's do not appear to carry antibodies against the disease; and
4. NIF's do not appear to harbour any viral particles.

The results so far obtained do not constitute scientific proof and more research is needed, but their immunisation procedure by which NIF's are produced by exposure to sick fish, is showing positive results, which in turn supports the above.

Let us not be overly hasty in dropping the name KHV. Allow science to do its job and come up with a suggestion.

(Disease never reported before).
Emergency report

Information received from Dr Peter Fernandez, Associate Deputy Administrator, International Services, United States

Department of Agriculture (USDA), Washington, DC:
Report date: 11 July 2002.
Nature of diagnosis: laboratory.
Date of initial detection of animal health incident: 24 April 2002.
Location & No. of outbreaks: Kernersville, State of North Carolina 1 hatchery complex comprising 6 farms
Description of affected population: koi carp (Cyprinus carpio).
Total number of animals in the outbreak*: Susceptible- 150 000, deaths- 15 000, destroyed- 135 000

* The figures refer to the fish population of the two farms that were affected out of a total of six farms in the complex.

Diagnosis:

1. Laboratories where diagnosis was made:
• The disease was diagnosed on 24 April 2002 at the University of Arkansas Diagnostic Laboratory at Pine Bluff, State of Arkansas.
• Diagnosis was confirmed on 5 July 2002 by the Centre for Environment, Fisheries, and Aquaculture Science (CEFAS), Weymouth Laboratory, United Kingdom (OIE Reference Laboratory for spring viraemia of carp).
2. Diagnostic tests used: tissue culture, immunocytochemistry.
3. Causal agent: spring viraemia of carp virus (rhabdovirus).

Epidemiology:

1. Source of agent / origin of infection: the source of infection has not yet been identified.
2. Other epidemiological details: the possibility of tracing the source of the virus is very limited. The establishment ships and receives fish on a weekly basis.The hatchery is located adjacent to a river and river water is used on the premises.

Control measures

1. As a result of the detection, 135,000 koi carp were destroyed at the hatchery.
2. All six farms in the hatchery complex are under quarantine.
3. The control plan is to depopulate and disinfect the tanks in the holding facility. A disinfection, decontamination, and testing protocol for spring viraemia of carp virus will be used to identify and maintain disease-free ponds and fish.
4. Fish and Wildlife authorities will be notified because this disease can affect common carp.

Aquarama'03 - A Call For Papers

The next Aquarama Conference will be held in Singapore between 29 May and 1 June 2003. It had issued a call for papers. Billed as the 3rd World Conference on Ornamental Fish Aquaculture, this meeting of leading industry and aquaculture experts is attracting keen interest worldwide. The two previous and highly successful staging of what has already become a highly prestigious event in the aquatic calendar, have combined the latest scientific findings with the hottest - and often most controversial - topics affecting the international ornamental aquatic industry.

For information about your submission contact Julian Lim at julian-lim@cmpasia.com.sg or visit their site at www.aquarama.com.sg for further details.

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