Koi Herpes Virus: A Review and Risk Assessment of Indian Aquaculture

Abstract

Common carp (Cyprinus carpio) is a widely cultivated freshwater fish for human consumption, while koi carp, is a farmed colored sub species of common carp used for ornamental purposes. Since 1998, both common carp and koi carp are severely affected by a viral disease called as Koi herpes virus disease (KHVD). This disease is caused by Koi herpes virus (KHV), also known as cyprinid herpes virus-3. The virus causes interstitial nephritis and gill necrosis in carps, so it is also termed as carp interstitial nephritis and gill necrosis virus. KHV is a double stranded icosahedral DNA virus belonging to family Alloherpesviridae, with a genome size of 295 kbp, larger than any member of Herpesviridae. The viral genome encodes 156 potential protein coding open reading frames. Each virion consists of forty structural proteins, which are classified as capsid (3), envelope (13), tegument (2) and unclassified (22) structural proteins. Diagnosis of KHVD is mainly based on detection of viral DNA by polymerase chain reaction amplification using specific primers or loop mediated isothermal amplification. Temperature dependent latent infection is unique to KHV; and carrier fish are often not detected, thereby possibly resulting in spread of this pathogen to newer areas. The disease is now known to occur in, or has been recorded from at least 26 different countries of the world. Fortunately, KHVD has not been reported from India or from Indian major carps. To monitor the disease status of the country, a total of 254 fish samples collected from different parts of India were screened by PCR for the presence of KHV. None of the tested samples were found to be positive for KHV. These results demonstrate that tested samples from different parts of India were apparently free from KHV. Preliminary risk assessment of KHV suggest that in the event of unrestricted importation of koi carps into our country, there is a higher probability of risk to aquaculture as compared to natural waters. So there is strong need to develop diagnostic capabilities and launch surveillance programmes for KHV in India.

Establishment and characterization of fin-derived cell line from ornamental carp, Cyprinus carpio koi, for virus isolation in India

“…Likewise, transmission of the KHV pathogen via live fish is a major problem worldwide (Hedrick 1996). In India, in a 3-yr disease surveillance programme, KHV has not been detected from koi carp or from Indian major carps (Rathore et al 2012). These lessons can assist us towards preparing better and improving responses in the event of KHV disease outbreaks in India.…”

“…CyHV-3 has become a globally distributed pathogen and affecting koi and common carps from at least 26 different countries of the world (Michel et al 2010;Maya et al 2011). Incidence of KHV disease has so far not been reported from India (Rathore et al 2012;Swaminathan et al 2013), in spite of KHV disease outbreaks happening in neighbouring Southeast Asian countries (Lio-Po et al 2009). However, unregulated and illegal international trade of ornamental fish, particularly koi carp can lead to introduction of KHV into India.…”

Establishment of caudal fin cell lines from tropical ornamental fishes Puntius fasciatus and Pristolepis fasciata endemic to the Western Ghats of India

“…However, very little information is available about the occurrence of viral diseases in the fish in Indian waters, which can be due to the lack of appropriate cell lines. Results of a recent PCR based survey shows that 254 freshwater fish samples collected from different parts of India were negative for the presence of KHV (Rathore et al, 2012). However, in marine fish, Azad et al (2005) reported mass mortality of Asian Seabass, Lates calcarifer due to piscine nodavirus infection from the Indian sub-continent.…”

Viral vaccines for farmed finfish

“…In 2010, mass mortalities associated with KHVD in wild common carp were reported from Canada. Outbreaks of KHVD have also been reported from a number of Southeast Asian countries between 2005 and 2009, and KHVD has now been reported from 26 different countries [71,81].…”

“…In late 90s, major outbreaks of KHVD occurred in the USA, Israel, and Germany [71,81]. In 2010, mass mortalities associated with KHVD in wild common carp were reported from Canada.…”