'Long-haired' water moulds are the most virulent

Jul 22, 2009
'Long-haired' water moulds are the most virulent
The last stage of the HeMP-methode. The water mould has a good growth - the medication does not work against Saprolegnia

The water mould Saprolegnia can cause skin disease in salmon during its freshwater phase. The mould attacks both fish and eggs and has at times caused great economic loss for the fish farming industry, both in Norway and in other salmon-producing countries. Saprolegnia infection may be seen with the naked eye as white patches on the skin or as "cotton-like" patches on eggs.

In his doctorate, Svein Stueland from the National Veterinary Institute showed that different strains of the water mould Saprolegnia vary in their ability to cause disease and mortality in farmed salmon. In addition, he developed a simple and effective method for testing new medications that may prove important for treating the disease.

Stueland's project grew out of a need for knowledge of the distribution of Saprolegnia and its disease-producing abilities. Such knowledge is necessary to develop better treatment methods against the disease. Earlier, the disease was effectively controlled with the dye malachite green, however, this substance is now forbidden and the fish farming industry needs new, effective and reliable medications against the disease.

During the study, Saprolegnia was collected from eggs and farmed salmon in Norway, Canada, Chile and Scotland. Significant differences in pathogenicity between the different strains of Saprolegnia were seen, with the mortality in salmon fry varying from zero to 89%.

The mould's appearance and its growth abilities are related to its ability to infect and produce disease in . The "long-haired" Saprolegnia, which also showed high growth rate early in its growth phase, had the greatest disease-producing ability. "Long-haired" Saprolegnia contains mould equipped with types of long hooks. Simultaneously, a connection was shown between the "genetic fingerprint" and the mould's pathogenic ability.

Molecular-biological analyses, or so-called fingerprinting, made it also possible to differentiate between the collected Saprolegnia . Genetic analyses revealed greater genetic variation in the moulds from particular countries, than between countries, indicating that Saprolegnia from Norway, Canada, Chile and Scotland share to a great degree a common genetic base.

As a part of his doctoral work, Stueland also developed a simple and effective method for testing the efficacy of medications for the treatment of this disease in fish farming.

The project was a collaboration between the National Veterinary Institute, the Norwegian School of Veterinary Science, PHARMAZ AS, Marine Harvest AS and the Norwegian Research Council.

Cand. med. vet. Svein Stueland defended his Ph. D. thesis, entitled "Saprolegnia infections in salmonids. Characterization of Saprolegnia species and search for new treatment of Saprolegnia infections", at the Norwegian School of Veterinary Science, on June 16, 2009.


The last stage of the HeMP-methode. The water mould has a good growth - the medication does not work against Saprolegnia

This picture shows that the tested medicament works - the water mould does not grow.

Source: Norwegian School of Veterinary Science (news : web)

Explore further: Researchers successfully clone adult human stem cells

add to favorites email to friend print save as pdf

Related Stories

Malaria makes relapsing fever more serious

May 08, 2009

Malaria and the Borrelia infection relapsing fever are diseases with similar symptoms that can occur simultaneously. In such cases, the malaria is moderated while the relapsing fever becomes more serious. This is shown in ...

The secretive immune system of the salmon

Jan 27, 2009

During his doctoral thesis, Erlend Haugarvoll discovered new aspects of the salmon immune system. His research looked at the immune cells in the gills of salmon and at immune responses to vaccination. A special ...

Recommended for you

Researchers successfully clone adult human stem cells

Apr 18, 2014

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Researchers develop new model of cellular movement

Apr 18, 2014

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

User comments : 0

More news stories

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.