The disease is also sometimes called koi sleepy disease. It is an infectious disease of fish, where they gravitate to the bottom of a pond or a river and display little movement. Physiologically, the eyes of the fish become sunken, the skin undergoes flaking and the gills become swollen. If the swelling of the gills progresses then the fish dies through lack of oxygen. The fish affected are mainly carp and koi. Carp is a general term for oily, freshwater fish including the silver carp, common carp and black carp. Koi are a specific type of ornamental carp, which come in a variety of colors including white, black, red, yellow, blue, and cream.
The type of virus and how it reacts is still a mystery to virologists. It is thought that the infectious virus is related to the small-pox family (although it is not hazardous to humans). The case in Austria has allowed scientists to begin exploring the disease in more detail, using the latest molecular biology methods bolstered by electron micrography.
Following the case in Austria, the disease has been found to affect fish in Germany, France, U,K., the Netherlands and other European countries. The disease tends to strike most often in the spring. The new cases suggest widespread infections among koi and carp stock around the world, with rates of infection increasing.
The transfer of the disease from Japan to Europe is a sign of the extent of the virus’ ability to spread. In addition, there are signs that the virus has mutated. In Japan the disease tends to strike when the water temperature is between 15 and 25 degrees Celsius; however, in Europe, where carp live in cooler waters, the disease appears when the water temperature is 7 to 15 degrees Celsius.
In September the spread of the virus and its likely future state will be discussed at the annual meeting of the European Association of Fish Pathologists. Some delegates have already begun calling for international action.
The cases of the infected Austrian fishes and the wider implications have been reported to the journal Transboundary and Emerging Diseases. The paper is called “Carp Edema Virus/Koi Sleepy Disease: An Emerging Disease in Central-East Europe.”
