Carp Herpesvirus (KHV)

Carp Herpesvirus (KHV) is a member of the family of herpesviridae. Carp Herpesvirus was first discovered in Israel in 1999 with first confirmed case in 1998 also in Israel. Cases have then been found in the U.S, Europe and Asia. Classified as a DNA-virus however this classification was under debate (Ronen et al.,2003) until more recent works by (Waltzek et al.,2004) where strong evidence linked it to its original classification.

The herpesvirus has DNA as its genetic material. It copies itself by utilising DNA-dependant DNA polymerase process; a process that occurs during DNA replication. In the herpesvirus the DNA is usually double stranded DNA (dsDNA) but can also utilise single stranded DNA (ssDNA). This DNA virus belongs to a classification system known as the Baltimore classification system and the herpesvirus could fall into groups I or II.

 

The Herpesvirus (KHV) can have an incubation period which is on average 14 days but can be longer depending on environmental conditions. Hartman proposed this could suggest that the water temperature is a secondary trigger and maybe required for an outbreak to occur (Hartman, n.d.). Early signs of the virus are hard to detect and the site or stock will require a laboratory and/or a fish health specialist to diagnose. The virus attacks many systems within the host as in case of the carp it effects the eyes, mucus system, gills and motor function. The attack on the systems of the fish make it more susceptible to infections from parasites, fungi and pathogens. These external factors of illness can be the final cause of death of the specimen. 

 

Typically the virus is transferred by contact with another affected specimen but can also be transferred through the water as well as through contact with equipment used by anglers and other water users that have not been treated/cleaned or maintained correctly. Infected but not killed specimens, known as carriers, will carry the disease for life and spread it to new stock and will need to be totally eradicated from the water to ensure further spread of the disease. Scientist are currently working on a vaccination for the disease but to date no treatment can save a specimen once it has been infected.