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28 July, 2003 : Vol 2 : No 2         

CONTENTS
- KHV is dead

- KLM continous live fish "comeback"

- New method for detecting fish skin diseases

- Four Species of Costia

- Koi Anatomy on the Web

- AQUARAMA 2003 - New date

- Koi Breeding, Production and Export Seminar

Back to Archive Index

KHV IS DEAD AND CNGV IS BORN

According to research findings in the press, the virus that has been the cause of high mortalities in Koi populations around the globe, has finally been isolated. 

In the forthcoming article Efficient vaccine against the virus causing a lethal disease in cultured Cyprinus carpio, Ariel Ronen of Department of Pathology, The Hebrew University-Hadassah Medical School, Jerusalem and his co-workers not only announces that an effective vaccine has been produced, but also that the virus previously known as Koi Herpes Virus (KHV) it is not a member of the Herpes virus family, and that renaming it is in order.

Abstract  We have isolated a virus, which causes a mortal disease in cultured ornamental Koi and Common carps (Cyprinus carpio) in many countries worldwide. This unclassified virus, which causes nephritis and gill necrosis, and so has been given the name carp nephritis and gill necrosis virus (CNGV), has a morphology resembling the herpes virus, but bears a genomic DNA of ca 250–300 kbp. So far, both others and we have been unable to find CNGV-DNA sequences possessing a significant similarity to known DNA viruses. The virus induces a lethal disease when water temperature ranges between 18 and 25 .C (permissive temperature). In this report, we demonstrate that carps, exposed to the virus at 23 .C for 3–5 days and then transferred to the non-permissive temperature of 30 .C, became resistant to a challenged infection and their sera demonstrated a high level of virus-specific antibodies. We have isolated attenuated non-pathogenic viruses that render virus-vaccinated carps resistant to the disease. Furthermore, vaccinated fish developed high levels of antibodies against the virus. We suggest, therefore, that this attenuated virus could be used as a live vaccine for the eradication of the mortal disease afflicting Common and ornamental carp fisheries in many countries. 

© 2003 Published by Elsevier Ltd.

SDK:- So carp nephritis and gill necrosis virus, is what it should be called in future. CNGV for short. And unless the name is seriously challenged in the scientific press, that is what it will remain. Better start practicing it so your tongue gets used to it. For your information: Nephritis refers to an inflammation of the kidney and necrosis to the dying of cells, the most specific symptoms of the disease. 

For those keen to know more:

Introduction:  During the last four years, a new disease causing high mortality has afflicted cultured ornamental and Common carps (Cyprinus carpio) in Israel. A similar disease was observed in the US, in Europe (Germany, Britain and The Netherlands) and in Asia (Indonesia, Japan and Korea) [1–6]. The clinical signs of the disease are fatigue, gasping movements in shallow water, sunken eyes, pale patches on the skin, increased mucus secretion as well as nephritis and gill necrosis [1]. This viral disease has caused severe financial losses to fish breeders, retailers and hobbyists world-wide. Although the disease is highly contagious and extremely virulent, morbidity and mortality are restricted to Koi and Common carp populations. Fish of several species, some of which are closely related, such as Oreochromis sp., Bidyanus bidyanus, Hypophthalmichthys molitrix, Carassius aurata and Ctenopharyngodon idella, were found to be completely asymptomatic to the disease even following long-term cohabitation with diseased fish. Moreover, fingerlings of these resistant strains sharing the same tank with diseased fish, failed to transmit the disease to na¨ýve sensitive carp upon a long cohabitation period [7]. In addition to the narrow host range, the epidemics in ponds are limited to the transient seasons of spring and fall, since the virus propagates only at a temperature range of 18–25 C. 

We isolated a virus causing the carp disease from kidney cells of sick fish. The virus propagates and induces severe cytopathic effects 5 days post infection in fresh Koi fin cell (KFC) cultures, but not in epithelioma papillosum cyprini (EPC) cells (submitted for publication). The virus harvested from KFC cultures induced the same disease, with a mortality of 75–85%, upon inoculation of naive Koi and Common carp. Polymerase chain reaction (PCR) with authentic primers provided final proof that the isolated virus is indeed the etiologic agent of Common carp and Koi mortalities in fish husbandry ([8,9], and our unpublished results). The isolated virus has an icosahedron morphology resembling herpes viruses [1], but its 277 kbp double-stranded DNA genome is larger than that of Herpesviridae family members [10]. The viral DNA sequenced so far ([8,9], GenBank accession no. 91AY208988-91 and our unpublished results) revealed that only small fragments (16–45 bp) are similar to known viral genomes. Moreover, partial sequence of thymidine kinase (TK) gene (GenBank accession no. AJ535112) revealed no resemblance to other known herpes virus TK genes, suggesting that the virus may represent an, as yet, unclassified species. 

We prefer, therefore, to designate it as carp nephritis and gill necrosis virus (CNGV), according to its pathogenic manifestations, rather than Koi herpes virus (KHV), as was originally suggested by Hedrick et al. [1]. In this report, we demonstrate that carps, exposed to the virus at 23 .C for 2–3 days and then transferred to the non-permissive temperature of 30 .C, become resistant to a challenge viral infection ("naturally resistant"). Elevated levels of specific anti-CNGV antibodies were found in the sera of these "naturally resistant" fish. In order to avoid infection of fish with a pathogenic agent, we isolated a non-pathogenic virus, which renders the carps resistant to the disease. The attenuated virus, which induces high serum levels of anti-viral antibodies, can be used as an efficient live vaccine. 

The rest of the article is too technical for general consumption, but those who crave for the juicy detail can email M. Kotler for the full text.

KLM CONTINUES LIVE FISH "COMEBACK" 

Dutch national airline (and OFI member) KLM has just announced the latest additions to its gradually 're-expanding' live fish transportation programme.

We've certainly come a long way since the worst of the crisis that followed the notorious 'Chinese Squirrels' incident of three summers ago when KLM felt bound to cease virtually all of its live animal activities. From 'Day 1', though, airline representatives have worked untiringly, exploring ways in which, at least, some services could be resumed. In this, they have received our full-hearted support and understanding.

Last year, after constructive discussions with animal protection groups within Holland, KLM felt able to restart its handling of shipments of wild-caught fish from Jakarta (Indonesia), Bogotá (Colombia) and Sao Paulo (Brazil). Once these operations had been running for a six-month period, the airline then carried out an in-depth study to evaluate the success or otherwise of their decision to resume their service from these stations. The outcome of this analysis was extremely positive, so much so, that they decided to expand their network accordingly. As a result, shipments of cultivated fishes were resumed from the following stations:

Singapore, Amsterdam, Tokyo, Osaka, Kuala Lumpur, Penang, Bangkok, Jakarta, Beijing, Tel Aviv, Hong Kong, Taipei, Shanghai and Cape Town.

Now comes further welcome news with the announcements of the resumption of wild-caught shipments from:

Lima, Curaçao, Manila, Bangkok, Singapore, Kuala Lumpur and Amsterdam.

In addition, Miami and Los Angeles will be opened "later this year", with Bali and Manuas being added as 'off-line stations' for wild-caught fish.

[NOTE : An off-line station is one from which there are no direct KLM flights. In these instances, KLM will be using a 'feeder flight' from these airports to one from which the airline has 'on-line' i.e. direct, services.]

We commend KLM for their ongoing efforts to restore their world-respected live fish service to the industry and have every confidence that further stations will be added to the list over the coming months.

For further details, please contact Hans Hartgers at: hans.hartgers@klmcargo.com

FOUR SPECIES OF COSTIA? 

At the 4 th International Symposium on Aquatic Animal Health, New Orleans Dr Heather Callahan of the North Carolina State University presented genetic evidence for more than one species of costia. On the basis of SSU rRNA, the parasite was described as a complex of at least four groups that probably represent different species. One group consisted of hybrid striped bass and swordtail isolates, the second and third group consisted of the rainbow trout and mirror carp isolates and the fourth group consisted of koi, goldfish, catfish and flounder isolates. This separation was geographical and related to fish movements.

SDK:- If you really need to know more about these little brats of intensive aquaculture, please contact the pesons above.

KOI ANATOMY 

If ever you need to know more about Koi Anatomy, just have a look at what Phil Ishizu & Spike Cover has to say at  www.akca.org

AQUARAMA 2003 - NEW DATE

The AQUARAMA conference that was postponed due to SARS will now be held 30 October - 2 November. The meeting is billed as the 3rd World Conference on Ornamental Fish Aquaculture. Sessions cover application of biotechnology in the ornamental fish industry; production of new ornamental species; culture of freshwater ornamentals; culture of marine ornamentals; new developments in the ornamental fish industry; and challenges and issues facing the ornamental fish industry. For more information contact julian_lim@cmpasia.com.sg or visit http://www.aquarama.com.sg/.

KOI BREEDING AND PRODUCTION SEMINAR

A Koi Breeding, Production and Export Seminar will be held on 27 September in Johannesburg. It's not everyday that the art of Koi Aquaculture is discussed openly from A - Z. For more information visit www.koinet.co.za 

Totsiens 

Servaas de Kock   

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OUR MISSION: This free Newsletter is intended to share information of interest to the Breeders, Exporters, Importers and Dealers of Koi internationally. It is not intended for the average hobbyist. Your feedback or criticism of whatever kind will be valued. If you want to update me on whatever is happening in your part of the world, I will be delighted. The idea is to serve the Koi industry and keep commercial content out. If I make mistakes, well, correct me if you can substantiate your claim. Please forward this to anyone you think might be interested in our subject matter.

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