aquaculture

Viral haemorrhagic septicaemia (VHS) was initially noted as a disease of cultured European rainbow trout (Oncorhynchus mykiss). The disease has been noted amongst marine species, notably farmed turbot (Germany, Scotland and Ireland), but until relatively recently (approximately Spring 2005), appears to have been restricted to Europe. Dr. Robert S. Bakal, of the U.S. Fish & Wildlife Service’s Division of the National Fish Hatchery System, reports from a conference on VHS held in August 2006,

…leading expert on VHS in the United States, Jim Winton of the US Geological Survey, indicated that the VHS virus exists in four strains, with a single, unique sub-strain occurring in the Great Lakes. The VHS virus has been known in Europe, Japan, and the coasts of the U.S. for many years; how it came to occur in the Great Lakes is not known. Winton speculates that it may have originated in ballast water from ocean-going ships sailing into the Great Lakes, or that it may have hitchhiked in shipments of hatchery-raised fish.

According to the New York State Department of Environmental Conservation (NYSDEC),

Viral hemorrhagic septicemia (VHS) virus is a serious pathogen of fresh and saltwater fish that is causing an emerging disease in the Great Lakes region of the United States and Canada. VHS virus is a rhabdovirus (rod shaped virus) that affects fish of all size and age ranges. It does not pose any threat to human health. VHS can cause hemorrhaging of fish tissue, including internal organs, and can cause the death of infected fish. Once a fish is infected with VHS, there is no known cure. Not all infected fish develop the disease, but they can carry and spread the disease to other fish. VHS has been blamed for fish kills in Lake Huron, Lake St. Clair (MI), Lake Erie, Lake Ontario, the St. Lawrence River and Conesus Lake (Western NY). The World Organization of Animal Health has categorized VHS as a transmissible disease with the potential for profound socio-economic consequences. Because of this, they list VHS as a disease that should be reported to the international community as an exceptional epidemiological (study of diseases in large populations) occurrence.

The NYSDEC has released revised Emergency Regulations Adopted to Prevent Spread of VHS.

Animal and Plant Health Inspection Service (APHIS) note the following species are susceptable: Atlantic cod Gadus morhua, Black crappie Pomoxis nigromaculatus, Bluegill Lepomis macrochirus, Bluntnose minnow Pimephales notatus, Brown bullhead Ictalurus nebulosus, Brown trout Salmo trutta, Burbot Lota lota, Channel catfish Ictalurus punctatus, Chinook salmon Oncorhynchus tshawytscha, Coho salmon Oncorhynchus kisutch, Chum salmon Oncorhynchus keta, Emerald shiner Notropis atherinoides, Freshwater drum Aplodinotus grunniens, Gizzard shad Dorosoma cepedianum, Grayling Thymallus thymallus, Haddock Gadus aeglefinus, Herring Clupea spp, Japanese flounder Paralichthys olivaceus, Largemouth bass Micropterus salmoides, Muskellunge Esox masquinongy, Pacific cod Gadus macrocephalus, Pike Esox lucius, Pink salmon Onchorhynchus gorbuscha, Pumpkinseed Lepomis gibbosus, Rainbow trout Oncorhynchus mykiss, Redhorse sucker Moxostoma spp, Rock bass Ambloplites rupestris, Rockling Onos mustelus, Round goby Neogobius melanostomus, Smallmouth bass Micropterus dolomieu, Sprat Sprattus spp, Turbot Scophthalmus maximus, Walleye Sander vitreus, White bass Morone chrysops, White perch Morone americana, Whitefish Coregonus spp, Yellow perch Perca flavescens.

APHIS has also released the Amended Federal Order Viral Hemorrhagic Septicemia (VHS) dated May 4, 2007. The purpose of this Federal Order is to prevent the spread of viral hemorrhagic septicemia (VHS) into aquaculture facilities. Also refer to the APHIS July 2006 Emerging Disease Notice – Viral Hemorrhagic Septicemia in the Great Lakes for further analysis.

Research reports published from the Scottish Fisheries Research Services may serve to provide management options:
Viral Haemorrhagic Septicaemia (VHS) – from the abstract:

Viral haemorrhagic septicaemia (VHS) was diagnosed inrainbow trout (Oncorhynchus mykiss) at a farm in Englandon 26 May 2006. VHS is a notifiable disease in the UK and a List II disease under European Directive 91/67/EEC. Investigations into the source and potential spread of the disease are being carried out by Centre for Environment, Fisheries and Aquaculture Science (Cefas) in England and Wales, and by Fisheries Research Services (FRS) in Scotland. VHS has occurred once before in the UK, in 1994, affecting a single turbot farm. The disease was successfully eradicated on that occasion. VHS has no implications for human health.

Risks to Wild Freshwater Fisheries from Viral Haemorrhagic Septicaemia (VHS) – from the abstract:

There is a risk of transfer of VHSV from farmed to wild freshwater fish species and vice versa. There is evidence that a reservoir of infection may be created in wild freshwater fish species. This may pose a risk of re-infection of farms (eg rainbow trout). There are no reports of VHSV infection leading to significant disease outbreaks in wild freshwater fish stocks. Based on evidence from outbreaks in farms and experimental evidence, free living rainbow trout, brown trout, whitefish, grayling and pike may be at risk of disease. Available evidence suggests a high infection pressure would be required to initiate a disease outbreak in wild fish (eg shedding of virus from an infected farm).

Disinfection guide version IV: practical steps to prevent the introduction and minimise transmission of diseases of fish – from the abstract:

Emerging diseases have had a significant impact on development of the Scottish aquaculture industry, highlighting the importance of preventing their introduction and minimising their transmission. The risk of disease spread is reduced by the implementation of good sanitary practices by fish farmers, and fisheries and the application of effluent disinfection systems in the processing industry. To maintain healthy fish stocks and minimise the introduction and spread of disease, the aquaculture industry should ensure best practice on farm sites, during transportation of live or dead fish and equipment, at the processing plant and during subsequent effluent and waste disposal. For an assessment of the risks associated with specific tasks, reference should be made to the Final Report of the Joint Government/ Industry Working Group on Infectious Salmon Anaemia (ISA) available from the Fisheries Research Services (FRS) web site, at www.frs-scotland.gov.uk. The protocols described in this guide are based upon current scientific knowledge and practical experience and will continue to be developed as the needs of industry change. This guide is intended for distribution to relevant industry personnel.

Aquaculture Health International is a new journal, with free .pdf format copies available for download. The publishers are based in New Zealand and so it is no surprise that the journal has a strong New Zealand emphasis, however the view is not limited to the New Zealand perspective.

Here’s the table of contents from the latest edition:
3 EDITORIAL – The European Commission Directive on Fish and Shellfish Health
4 DIAGNOSTIC LABORATORY SERIES – ADL Diagnostic Chile Ltda
7 FOCUS: FISH HEALTH MANAGEMENT EVENT IN POLAND
8 NEWS – Updates from around the globe
10 REPORT: PROBIOTICS IN TROUT FEED – The benefits of probiotics in aquaculture: a two-year study
12 FOCUS ON FINFISH – Diseases of kingfish (Seriola lalandi) in Australasia
15 FOCUS: THE MARINE HARVEST TRIALS UNIT IN SCOTLAND – The Trials Unit broadens its focus from salmonids to other species
16 DISEASE PREVENTION FOCUS – Farm-level biosecurity and white spot disease of shrimp
21 FOCUS: AQUAFIN CRC AND SOUTHERN BLUEFIN TUNA HEALTH – Southern bluefin tuna are Australia’s most valued cultured finfish
23 FOCUS ON RESEARCH – The effects of AquavacTM ErgosanTM on juvenile Chinook salmon

The aim of the Aquatic Animal Health Code (Aquatic Code) is to assure the sanitary safety of international trade in aquatic animals (fish, molluscs and crustaceans) and their products. This is achieved through the detailing of health measures to be used by the veterinary authorities of importing and exporting countries to avoid the transfer of agents pathogenic for animals or humans, while avoiding unjustified sanitary barriers.

The health measures in the Aquatic Code (in the form of standards, guidelines and recommendations) have been formally adopted by the OIE International Committee. The 7th edition incorporates the modifications to the Aquatic Code agreed during the 72nd General Session in May 2004. These include revised chapters on the following subjects: general definitions, Disease listing and notification criteria, notification and epidemiological information, obligations and ethics in international trade, Aquatic animal health measures applicable before and at departure, Aquatic animal health measures applicable on arrival, General recommendations on disinfection and the model international aquatic animal health certificates.

The purpose of the Manual of Diagnostic Tests for Aquatic Animals (the Aquatic Manual) is to provide a uniform approach to the diagnosis of the diseases listed in the Aquatic Code, so that the requirements for health certification in connection with trade in aquatic animals and aquatic animal products, can be met.

Although many publications exist on the diagnosis and control of aquatic animal diseases, the Aquatic Manual is a key document describing the methods that can be applied to the OIE-listed diseases in aquatic animal health laboratories all over the world, thus increasing efficiency and promoting improvements in aquatic animal health world-wide.

The Aquatic Code and the Aquatic Manual are both available online, for free.

The strength of Australian aquaculture lies in its disease-free status and reputation for providing clean, green products. Many serious infectious diseases, which limit aquaculture production overseas, remain exotic (foreign) to Australia. However, experience overseas shows that as fish production intensifies, the incidence of diseases also increases.

Exotic disease outbreaks are a significant threat to Australian aquaculture. In a suspected outbreak, disease control is the responsibility of State fish health authorities, who are supported by the CSIRO Australian Animal Health Laboratory (AAHL) Fish Diseases Laboratory (AFDL). This facility is managed by CSIRO Livestock Industries.

Finfish diseases, especially salmonid diseases, have been studied for many years and most can be tested for at AFDL. However, as Australians begin culturing different species, new diseases are likely to occur.

Fast and accurate disease identification is crucial in containment of a disease outbreak. Many fish diseases are manifest by similar disease signs such as skin lesions, sluggishness and loss of balance, condition and appetite. Laboratory tests often provide the only means to diagnose a disease with certainty to ensure that appropriate disease controls are implemented.

The AFDL is an integral part of CSIRO’s Australian Animal Health Laboratory (AAHL), a national facility specialising in research and diagnosis of animal and fish diseases, especially exotic diseases. This means AFDL scientists are ideally placed to diagnose both exotic diseases and newly emerging diseases.

As a diagnostic and research laboratory, AFDL has four major roles:

* disease diagnosis and identification of infectious agents (pathogens)
* development of diagnostic tests for exotic diseases
* training and technology transfer
* export certification testing and health surveillance.

In CSIRO AAHL’s microbiologically secure research facility, exotic disease agents can be studied without risking accidental release to the external environment. The CSIRO has released a list of diseases of concern to aquaculture.

The David Suzuki Foundation web site has released (March 29, 2005) a report entitled: “Fish farm causes sea lice abundances thousands of times higher than natural levels, new study confirms”

The results show transmission of lice from farmed salmon to migrating wild salmon peaked at an intensity of 70 times greater than natural near the farm and continued to exceed natural levels for 30km along the migration route. This amounts to a total contribution of lice from the farm that was 30,000 times higher than natural.

There are documents outlining the research methods and results available for download from the above link.

The Foundation has begun examining sustainable aquaculture practices and has found, in the British Columbia region of Canada, aquacultural practices are “polluting the environment and seriously threatening the integrity of wild stocks”.