Koi herpes virus

The koi herpesvirus infection is a by the Koi herpes virus ( KHV) caused epidemic-like, acute to subacute running viral infectious disease of carp and koi carp. It is since the end of 2005 in Germany a notifiable disease.

The incubation period is dependent on various factors such as stress and the particular condition of the fish, from one week to several months. If there is an outbreak of disease, the mortality rate is usually between 80 % and 100 % in a period of 24 hours to 14 days.

Pathogen

Koi herpesvirus ( KHV) was described by Hedrick Ron of the University of California, Davis herpes virus in 2000. It is not yet known whether this virus with the herpes virus cyprini, which was already described in 1990 in Japan, is the same. Is classified as the Koi herpes virus DNA virus of the Herpesviridae group of viruses (herpes viruses). For the first time occurred and described the virus in 1998 in Israel.

The pathogen is found in Koi and Nutzkarpfen. Other non- congeneric cyprinids such as grass carp ( Ctenopharyngodon idella ) or Goldkarausche (Carassius auratus) seem to stay on the virus does not always unaffected. Backed this information is in that KHV has been detected in goldfish and they, if they do not get sick, act as intermediaries. What is certain is that the virus only infects carp fish.

Transmission

Like most viruses, even the Koi herpes virus is transmitted by direct contact. This can be self- skin contact and gill excretions, water or other liquids have been in contact with infected fish, the fish. The handling in the water with the hands, or work with objects such as dip nets or nets or contact with the footwear are already sufficient to transmit the virus. Water birds can also bring the virus into the water, although the virus does not survive more than two hours outside of its habitat. Without a carp as a host, the virus survived up to 14 days in the water. In most cases, the virus is kidnapped by Additions of fish in the stock.

Course of the disease

The disease course is rather non-specific and many of the symptoms that occur are masked by other diseases or occur as a secondary infection in appearance, then do not let the close on KHV infection. Among these are especially bad water parameters (ammonia, oxygen deficiency, overfeeding or poorly functioning filter systems ) to call but also bacterial diseases that you can bring in to the pond. However, in the temperature range between 18 ° C and 25 ° C, the highest loss rates are observed. The outbreak of the disease is possible already at 8 ° C. Thus, the virus must have adapted to European standards according to the findings of the latest research. At temperatures above 30 ° C and 4 ° C (in vitro conditions ) does not appear to be infectious, the koi herpes virus. The disease is also influenced significantly by other environmental and husbandry conditions (water quality, stocking density, stress).

The clinical picture has the following symptoms:

• Apathy
• Secretion from the swarm
• Increased mucus
• Shred -like mucus detachment
• Gasping at the surface
• Necrosis of the gills (white or red patches)
• Necrosis and hemorrhage in the skin
• Loss of appetite or anorexia
• Sunken eyes
• Be upside down
• Color loss
• Rough skin (sand paper effect )
• Bleeding in and around organs
• Necrosis in organs
• Swollen spleen
• Altered kidney

Pathologically, the koi herpes virus infection by an interstitial nephritis, inclusion in gills or intestine, beamforming on the gills, giant cell formation and an altered blood picture is characterized.

Diagnosis

The pathogen can be detected by polymerase chain reaction (PCR) or LAMP- test (Loop - Mediated Isothermal Amplification ) (see Koi herpes virus detection).

Quarantine

In quarantine suspicious disease must as well as freshly imported animals. This also applies to conditional weak animals. In valuable animals, the ponds with nets must be secured against bird flight. New Items are for at least 14 days to put at least 20 ° C separately, ideally at different temperature ranges and a duration of approximately four weeks. After two weeks, there are no symptoms of illness should be seen at least a Koi, better two, to be implemented from the existing pond for Neuzukauf to quarantine. The introduction of new items in the older parts must be avoided under all circumstances.

Embarrassing hygiene of equipment and people can counteract well contamination Koipopulation. It is strongly recommended that Kois derived from KHV known areas such as China, Israel, Japan and Thailand prior to introduction into koi ponds for the above Time are to be kept in quarantine. Buyers should only retailers acquire animals that screen their koi by PCR analysis, proof of negative results from a veterinary recognized institution can demonstrate and have the appropriate quarantine facility. For traders who do not provide such proof, it should not be a purchase. Similarly, a mixture of animals of different origin areas should be avoided. The acquisition of so-called immunized (not to be confused with vaccinated! ) Animals could be considered critical, since these animals can carry the pathogen latently infected and healthy stocks so again. Such fish are with the introduction of a true vaccine (see below), since around 2006, no longer commercially anyway. KHV can be very contagious. A contaminated water splashes can be enough to endanger the whole stock.

Treatment

Treatment with Cure is not at the present time. Infected animals can with an increase in temperature of about 30 ° C over a period of about 30 days so treated ( immunized ) are that they can live with the virus. However, these animals, if they survive to vectors (carriers). These carriers can then at any time raise infectious viruses in circulation, which nonimmune attack animals and can kill them. If the disease has broken out culled under certain circumstances, the entire portfolio and the pond to be drained. Then an intense Desinfizierungsbehandlung should be done.

According to R. Hoffmann (Institute of Zoology, Fisheries & Fish diseases d LMU Munich) are immunizing action against herpes viruses in animal husbandry in general is particularly problematic because you have to do it with the herpes virus-infected animals with lifelong carriers of the virus. Therefore, the vaccination of healthy animals could lead to a vaccination, but this does not guarantee that the vaccinated animal is also not in contact with the herpes virus to an unrecognized virus carriers. Therefore, herpesvirus vaccines are not capable to eliminate the disease from animal populations. Especially the carrier (ie the healthy virus carriers ) it, in the course of their lives leaving us, after his observation repeatedly viruses and so far could not infect animals are infected.

This view stand in the way currently to the contrary experience of Israel that survived a severe epidemic with extreme losses and protected by vaccines carp production has successfully built new.

The inoculated animal suffering not, the not yet infected Koi seriously ill and dies in most cases. Despite claims to the contrary has not been proved that with the aforementioned vaccine have ever transmitted field virus -vaccinated fish.