The previous discussion of ISA, and a brief mention of IHN, with Sockeyefry - brings to mind the other known potential diseases and parasitic transfer through the technology of the open net-cage and other interactions between wild and cultured fish. We often forget to mention these other risks, since the sea lice risk is so apparent, critical and is being examined. The other risks have largely - not been looked at.
These potential disease and parasite interactions could be due to a variety of wild/cultured stock interactions, including:
1. direct release of disease and parasitic vectors in waters cohabitated by wild stocks in the vicinity of the net-cages through individually-diseased fish or by release of disease and parasitic vectors in or on the sediments and benthos,
2. the interaction of escaped diseased farm stock in either the marine or freshwater environments with wild stocks of salmon or other species, and
3. the potential for disease transmission by other carriers, including sea lice or other crustaceans (e.g. prawns), avian predators (e.g. herons, gulls, etc.), shellfish (e.g. mussels), or other organisms (e.g. marine mammals).
The following is a partial list of some of the more important salmonid diseases that typically can infect netcage and/or wild fish:
Viral Diseases
•Viral Hemorrhagic Septicemia (VHSv) – VHSv is an Egtved virus, mainly affecting rainbow trout (O. mykiss). Vertical transmission of disease. Symptoms: darkening of the skin, bulging eyes, pale gills, the body cavity is filled with yellowish fluid, discoloured kidney.
•Infectious Hematopoietic Necrosis (IHNv) – A RNA rhadovirus virus, highly virulent to chinook (O. tshawytscha), sockeye (O. namaycush) and steelhead (O. mykiss). Also affects Atlantic salmon (S. salar). Vertical transmission of disease. Causes anemia. No effective treatment, often 100% mortality. Low-temperature disease. Juvenile salmon and fry are particularly at risk. Symptoms: lethargy, equilibrium problems, pale gills, bleeding at base of fins, opaque faecal casts tailing at vent, abdominal swelling.
•Infectious Pancreatic Necrosis (IPNv) - A virus, difficult to eradicate. Mortality often reaches 85% among young fish. Survivors become carriers for life. Symptoms: erratic swimming,corkscrewing, internal bleeding. Horizontal and vertical transmission of disease.
•Infectious Salmon Anemia (ISAv) - A virus, difficult to eradicate, not yet found in BC, but now found in the Pacific for the first time - in Chilean fish farms. Symptoms: Kidney and spleen hemorrhaging. No known cure.
•Lymohocystis – A DNA iridovirus. Common disease of marine and estuarine fishes, highly contagious. (O. tshawytscha). Symptom s: white nodules on fins, head and sometimes body of fish. Caused by encapsulation of connective tissue cells. Affects value of fish. No known cure.
•Marine anemia - see IHNv
Bacterial Diseases
•Bacterial Kidney Disease (BKD) (Renibacterium salmoninarium) - a gram-positive KD bacterium, especially affects adult chinook (O. tshawytscha). Also affects Atlantic salmon (S. salar). Normally 20-50% mortality in outbreaks. Infection usually happens in freshwater, mortalities in saltwater. Symptoms: Eye lesions, blisters, internal white or gray pustules in kidneys. Treatment: vaccination (preventative) and erythromycin, gallimycin, ovadine, and betadine. Horizontal and vertical transmission.
•Bacterial Hemorrhagic Septicemia (BHS) (Aeromonas hydrophila) - gram negative bacterium. Symptoms: red ulcers, distention of abdomen, blood in intestine. Treatment: oxytetracycline, nitrofurazone, chloramaphenical.
•Enteric Redmouth Disease (Yersina ruckeri) - a KM bacteria. Treatment: vaccines (preventative), and terramycin, furazolidone, sulfamerazine, sulfamethazine, sulfamerazine, ovadine, and betadine.
•Furunculosis (Aeromonas salmonicida) - Gram negative bacterium. Affects Atlantic salmon (S. salar). More virulent at temps > 18oC. Affected fish may become carriers. Symptoms: Necrosis of musculature and internal organs, bleeding at base of pectoral and pelvic fins, swelling and red blisters. Treatment: vaccines (preventative) and oxytetracycline, terramycin, furazolidone, sulfamerazine, sulfamethazine, sulfamerazine, ovadine, betadine, oxolinic acid, and amozillin. Adding vitamins E and C to farm diet helps.
•Vibriosis (Vibrio anguillarum, V. salmonicida and V. ordalii) - Symptoms: Red inflamed areas, and possibly lesions on skin, in musculature and bloody fluid in body cavity. Treatment: vaccination (preventative) and oxytetracycline, oxolinic acid, sarafloxin, erythromycin and streptomycin.
Fungal Diseases and Parasites
•Saprolegnia (Saprolegnia parasitica) - a fungus. Also called "cotton mouth". Treated with malachite green and/or Betadine. Can cause deaths through suffocation if left untreated. High ammonia levels encourages growth of fungus. Treatment: Adding vitamin C to farm fish diet helps.
•Ich (Icthyophthirus multifilus) - a ciliated protozoan parasite. Also called "white spot disease". Can be lethal to freshwater fish. Adult parasite (trophonts) encysts and releases juveniles (theronts) which embed in fish and causes nodules to form on skin. Treat free-swimming stages only. Treatment: formalin, malachite green, copper sulfate, salt baths.
•Ceratomyosis (Ceratomyxa shasta) - A freshwater parasite, no known treatment.
•Whirling disease - A myxosporidian parasite, not yet known to be found in Canada, except possibly in the Columbia River drainage. Especially affects rainbow trout (O. mykiss). Causes swimming problems and skeletal deformities. Horizontally transmitted.
•Sea lice (Lepeophtheirus salmonis and Caligus clemensi) - An external parasitic copepod. The copepod can be a vector for other diseases. Especially affects Atlantic salmon (S. salar), also coho (O. kisutch) and chinook (O. tshawytscha). Treatment: hydrogen peroxide, pyrethin, ivermectin, Neguvon, Nuvan, or azamethipos.
•Trichodina (Trichodina sp.)- An external hookworm parasite. May occur on body, skin, fins, and gills. Treat with formalin and acetic acid. Treatment: formalin, acetic acid, salt baths.
•Soft flesh (Kudoa thyrsites) - A parasite that infects the muscles. Affects Atlantic salmon (S. salar), probably not Oncorhynchus spp.
•Eye parasites – anecdotal evidence that arrowtooth flounder found near fish farms are more exposed to this parasite.
I believe that one of the other problems with fish farms is that they often become a nexus of disease and parasite transfer; is because they draw fish together near the cages to interact and stay – which then allows and promotes transfer of diseases and parasites.
Not only are there uneaten feed pellets which attract fish, but shrimp and prawns are attracted to the accumulation of fish faeces (i.e. poo) – which draw fish in that are attracted to the shrimp and prawns. The physical structures also provide shelter for wild fish, as well as the lighting of the structures at night attracts fish and prey of fish.
All of this attraction to wild fish and combined length of stay and potential for interactions – means that fish farms are the equivalent of aquatic truck stops. If only 1 person had TB at a truck stop, and sneezed on only a few people – the results could be grave.
Only difference is – with fish farms, we wouldn’t see it – or notice it right away. Out of sight - out of mind.
Sockeye states: "Regarding the Rainbows and ISA, when the outbreak in Norway occured, they tested to see if their farmed rainbows were at risk. They found that they could carry the virus, but not be affected by it". - meaning farmed rainbows were probably the carriers.
Furthermore he writes: "Eradicated was probably the wrong word, more like controlled. ISA was a problem in NB in the 90's, and through the implementation of strict protocols, it seems to be under control as it has not reached the previous levels. BTW no wild atlantics were ever found with the disease. That is peculiar because usually there is a source identified, ususally from the wild population." - again - meaning farmed Atlantics were probably the carriers
Like I said "out of sight - out of mind".
I find it more than a little scary that ISA is in Chile - in the Pacific, now.
http://www.nytimes.com/2008/03/27/w...07195200&en=219732e22628748c&ei=5070&emc=eta1
(Thanks for the postings, Nerka, Old Black Dog and Dave H.)
Chile does not have wild salmon. The only possible source is from farmed salmon. Now they brought that disease (with no cure except death) - into the Pacific. Chile is not that far away, with respect to some highly migratory species. Look at how far fish like tuna swim.
Is ISA only known to affect salmon? Will the forage fish/fishmeal industry take a hit? Could escaped farmed salmon carry ISA? Could other species (esp. tuna or a secondary bird host?) carry ISA? Could other fish species (or a secondary host) pass it along - even as far as our waters, now?
What assurances do we have that it will not happen? Look at how far and fast some diseases like bird flu, mad cow disease, etc - have travelled..
Isn't that a scary concept? Do you really think the industry is so benign? Want some more examples of aquatic transfer?
•Ichthyophonus, often infects perch (Sebastes aultus) and yellowtail rockfish (Sebastes flavedus),
•Pacific hake (Merlucius productus) carries Kudoa (Kabata and Whitaker 1986) which is a known problem in net-cage operations,
•rockfish (Sebastes sp.) can be infected by a herpesvirus (Kent and Myers 2000),
•commercially-important rockfishes (Sebastes spp.) can get bacterial infections (Kent et al. 2001),
•Pacific herring (Clupea harengus) L. can also be infected with sea lice (Caligus elongatus) (MacKenzie and Morrison 1989), viral erythrocytic necrosis (VEN) and BHS (Traxler and Bell 1988),
•flounders (Anstensrud 1992), and juvenile gadids (Neilson, et al. 1987) are susceptible to sea lice, and
•pen-reared and wild-caught salmon can harbour the larval Anisakis simplex (herring worm) (Deardorff and Kent 1989).
•BKD is capable of surviving for up to 21 days outside the host in sediment/faecal matter; sufficient time to ensure successful horizontal transmission to nearby salmonids (EVS 2000),
•The mussel Mytilus edulis could act as a reservoir of BKD (Paclibare et al. 1994),
•Vibriosis and furunculosis have been detected in sediments beneath salmon farms 1.5-3 years after a farm was abandoned (Husevag et al. 1991, 1995, Enger et al. 1989). Many Vibrio spp., which includes Vibrio cholera that causes cholera in humans, as well as Vibrio parahaemolyticus, are becoming recognized as a human health risk (
http://www.shellfishquality.ca/vibrio.htm),
•Shellfish, including crusteaceans, could be involved in the mutual transmission of vibriosis to/from net-cage fish and shellfish beds (Greenberg et al. 1982, Kelly and Dinuzzo 1985, DePaola et al. 1994, Croci et al. 2001),
•Furunculosis has been transmitted between net-cages over distances of 24 km (EVS 2000),
•Sediment enrichment and anoxia conditions that develop beneath net-cages, promote colonization by tubificid worms (Brinkhurst 1982, Gray 1979) which are known to be intermediate hosts for myxozoan parasites,
•the sea louse Lepeophtheirus salmonis could be a vector or secondary host to a variety of diseases and parasites that infect fish (Nylund et al. 1991), including IHNv (Johnson et al. 1996), ISA (Nylund et al. 1993, Rolland and Nylund 1998), Aeromonas salmonicida (Nese and Enger 1993), and platyhelminthes (Minchin and Jackson 1993), and
•Otters can carry Yersinia ruckeri (Collins et al. 1996). There may be a wide variety of other bacterial and viral diseases, along with parasites that can potentially infect otters, or other fisheating mammals, including minks (Mustela vison), river otters (Lontra canadensis) and harbour seals (P. vitulina), for example.
Think the open net-cage is a good technology?
Will it be in the next ten years most likely not
