investigating the cause of koi fish deaths in a breeding and recreational complex in karaj city

Koi fish or ornamental carp (scientific name: cyprinus rubrofuscus koi) is a decorative and cultivated carp with different and beautiful colors and is kept as an ornamental fish in ponds, ponds, and aquariums. in the past few decades, many enthusiasts among people in the west and other parts of the world have turned to breeding koi fish or common ornamental carp (colored carp). breeding and keeping this ornamental fish has become a fun thing and an employment-generating and profitable tool, and compared to the breeding of other pets, it has a higher historical record and cultural level among the people. on a visit to a recreational complex with koi fish breeding ponds, it was found that with the warming of the new fish collection, after one week, the purchased fish suffered thirty percent losses. after the examinations, seeing the pale spots on the external surface and severe necrosis of the gills, the cases were suspected of koi herpes virus (khvd) and the disease was confirmed by positive pcr. koi herpesvirus disease (khvd) has spread worldwide since 1996 and affects fish of various ages, often resulting in 80-100% mortality in susceptible populations when the water temperature is between (16-25°c) as with other herpesvirus infections, khv may persist in infected fish for life. therefore, fish that recover from khv outbreaks should be considered as carriers of the virus.