Herpesvirus Diseases in Fish

By PetMD Editorial on Jul. 28, 2008

Herpes Virus


Herpesvirus is not only a human virus; it can just as easily infect fishes, too. In fishes, herpesvirus infections can cause a variety of diseases, including those can be fatal to the animal.


Channel Catfish Virus (CCV) is a serious herpesvirus infection in the fry and fingerling -- both fish young -- of the channel catfish. CCV usually infects weak fishes that are stressed due to shipping and handling, a lack of oxygen in the water, or chemically treated water. Fishes which are older have higher survival rates than younger fishes, and those older than one year of age are rarely infected by CCV. The infection, however, can be passed from a fish to its eggs.


The signs of CCV include an accumulation of fluids in the abdomen, enlargement and bulging of the eyes, and bloody fins. Destroying an infected fish and a thorough cleaning of its environment are the only ways to stop the spread of the CCV infection.


Herpesvirus disease of salmonids has two types: HPV-1 and HPV-2. Fishes with HPV-1 have enlarged eyes and an accumulation of fluids in the abdomen; their internal organs and muscles will also swell and accumulate fluids. HPV-1 infection is usually seen in trout species.


HPV-2, on the other hand, infects rainbow trout, coho, kokanee, masou and chum salmon. Fishes with HPV-2 commonly develop cancer on their jaws and on the skin of their fins. Symptoms for this infection include lethargy, loss of appetite, and darkened and bloody pigmentation of the fish's body wall.


Herpesvirus disease of turbot occurs in both wild and cultured turbots – a flatfish native to the marine or brackish waters of the North Atlantic. The infection deforms the skin and gills of the fish, leading to breathing difficulties. Therefore, turbots with this form of herpesvirus need to be kept in water with a higher oxygen content.


Herpesvirus disease of koi is a recently discovered infection in koi – an ornamental domesticated variety of the common carp.


The gills of the infected fish show serious tissue damage. Due to death of gill tissue, the fish are unable to breathe and have acute respiratory distress accompanied with lethargy. Mucus secretion can be seen on both the gills and skin of the infected fish.


Unfortunately, this particular herpesvirus is fatal for most koi and there is no known treatment. Therefore, any infected fish(es) and the environment need to be destroyed to keep the infection from spreading to other fishes.


Carp pox (or fish pox) is a herpesvirus disease that not only infects carps, but other fishes, too. The initial herpesvirus infection shows up as raised milky skin lesions that are smooth. Severely infected fish develop papilloma tumors on the skin, leaving it disfigured. Also, fishes with the disease may succumb to secondary bacterial infections.


To prevent the spread of fish pox, the environment and any infected fish(es) should be destroyed.

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