Distribution of the introduced cyprinid herpesvirus 3 in a wild population of common carp, Cyprinus carpio L.

Abstract

Cyprinid herpesvirus 3 (CyHV-3), which causes a lethal disease in common carp, Cyprinus carpio L., and koi, C. carpio koi, first occurred in Lake Biwa, Japan in 2004. To elucidate distribution of CyHV-3 in a wild common carp population, we conducted a PCR survey of CyHV-3 among such fish in Lake Biwa in 2006. Only 6% (1/18) of the common carp smaller than 300 mm were positive with PCR, whereas 31% (18/58) of fish larger than 300 mm were positive. To evaluate their past exposure to CyHV-3 infection based on the presence of antibodies, we also measured the levels of serum anti-CyHV-3 antibodies in the carp, using an enzyme-linked immunosorbent assay. None (0/26) of the fish smaller than 300 mm was positive for the antibodies, whereas 54% (33/61) of fish larger than 300 mm were positive. Of the antibody-positive individuals, 44% (14/32) were also positive by PCR strongly suggesting that wild common carp that survived infection become CyHV-3 carriers. Five individuals were positive by PCR but negative for antibodies indicating that their infection with CyHV-3 had occurred recently. These results suggest that transmission of CyHV-3 from carriers to naïve common carp is still occurring in Lake Biwa.

Transmission dynamics of an emerging infectious disease in wildlife through host reproductive cycles

“…This pattern was previously described for the common carp population in Lake Biwa in 2006 (Uchii et al, 2009). In this study, we found an identical trend in 2008 and 2009 (Figure 2), suggesting that newly matured hosts were subject to CyHV-3 infection in every year sampled.…”

“…Serum anti-CyHV-3 antibodies were quantified using the enzyme-linked immunosorbent assay (ELISA) according to Uchii et al (2009), with some modifications. Pooled sera of 10 wild common carp diagnosed CyHV-3 positive by PCR were used as a positive control and pooled sera of 10 cultured common carp never exposed to CyHV-3 were used as a negative control.…”

“…Interestingly, the breeding season coincides with a rise in water temperature to over 15-18 1C in the spring (Barus et al, 2002), which is optimal for the growth of CyHV-3 (Gilad et al, 2003). Furthermore, a survey of the prevalence of CyHV-3 antibodies in the common carp population of Lake Biwa in 2006 indicated that infection occurred primarily in adult fish (Uchii et al, 2009). Together, these findings suggest that the breeding sites are hot spots of CyHV-3 transmission.…”

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

“…KHV can become latent inside the leukocytes of healthy koi with probable exposure to the virus. In wild populations, KHV can remain as carrier in asymptomatic fish and act as reservoir of infection [83]. Several months after initial exposure to the virus, temperature-dependent reactivation of KHV infection can occur in exposed fish [19,78].…”

“…These antibodies are detected in the serum at 3 weeks after experimental infection and in survivors after 1 year following a natural infection [1,39,78,81]. KHV infection induces a high prevalence (54 %) of KHV specific antibodies in surviving wild fish population [83]; while studies in farmed fish of England show almost 85-93 % of fish are seropositive by ELISA, even 1 year after disease outbreak [81]. This indicates that ELISA is a valuable method of establishing previous exposure of KHV in apparently healthy fish.…”