Infectious hematopoietic necrosis virus antibody profiles in naturally and experimentally infected Atlantic salmon Salmo salar

Abstract

Atlantic salmon Salmo salar naturally and experimentally exposed to infectious hematopoietic necrosis virus (IHNV) in British Columbia, Canada, developed antibodies against the virus. More than 50% of the fish exposed to IHNV remained seropositive for several months after the IHN epizootic had subsided. The virus itself could not be detected in asymptomatic fish once the fish had recovered from IHN. The persistence of IHNV-specific antibodies in a large percentage of Atlantic salmon, from 4 different populations that survived an outbreak of IHN, and the lack of IHNVspecific antibodies in fish with no history of the disease, suggests that serology may be a useful tool for determining previous exposure to the virus. It may be important to determine whether Atlantic salmon have been infected with IHNV because, although the virus is difficult to detect in asymptomatic fish, an incidental finding suggests it may persist in a small number of fish after the outbreak has subsided. Furthermore, the presence of seropositive fish would be an indication that the virus may be enzootic at a farm, and such information would thus aid producers with stocking decisions. KEY WORDS: IHNV · IHNV-specific antibodies · Surveillance · Convalescent carrier state · Atlantic salmonResale or republication not permitted without written consent of the publisher Dis Aquat Org 46: 7-14, 2001 1996). Antibodies against IHNV were first reported in rainbow trout Oncorhynchus mykiss in the early 1970s (Amend & Smith 1974). Subsequent studies, using natural and experimental bath exposure to IHNV in rainbow trout, revealed a strong antibody response within 6 wk ) to 2 mo of exposure (Hattenberger-Baudouy et al. 1989. In addition, antibodies were detected in a large percentage of fish for several months after exposure to the virus (Hattenberger-Baudouy et al. 1989, Ristow et al. 1993. The long duration of IHNV-specific antibodies in trout populations infected with the virus, and the absence of these antibodies in non-infected fish, makes serological analysis a potentially useful tool (Hattenberger-Baudouy et al. 1989, LaPatra 1996.A preliminary study done by LaPatra (1996) suggests that Atlantic salmon exposed to IHNV electropherotype 1 produce virus-specific antibodies. Serology may therefore be a useful tool in this species of fish. However, before this methodology could be used by the British Columbia aquaculture industry in their surveillance program, it had to be validated.One of the objectives of this study was to describe the antibody profiles for Atlantic salmon after laboratory exposure to an IHNV isolate from British Columbia, Canada. The second objective was to determine whether the antibody profile of fish exposed to IHNV in a laboratory was consistent with what was observed in British Columbia when Atlantic salmon in salt water net-pen sites were naturally infected with the virus. MATERIAL AND METHODSLaboratory exposure experiment. Two separate groups of post-smolt 1 Atlantic salmon (McConnell X Mowi strain) were used in this...

Negligible risk associated with the movement of processed rainbow trout, Oncorhynchus mykiss (Walbaum), from an infectious haematopoietic necrosis virus (IHNV) endemic area

“…Viral RNA and truncated particles were detected in kidney, spleen and liver tissues; however, reactivation and recovery of infectious virus from such latently infected animals could not be demonstrated. In a recent study in Atlantic salmon, Salmo salar L., an incidental finding suggested that IHNV may persist in the anterior kidney in a small number of fish once the IHN epizootic has subsided (St‐Hilaire, Ribble, LaPatra, Chartrand & Kent 2001). As these organs are removed during gutting of cultured rainbow trout, any risk associated with their involvement in a potential latent or persistent carrier state is negligible in the finished product.…”

Review of infectious agent occurrence in wild salmonids in British Columbia, Canada

“…Wild salmon mortality is one of the indicators of salmon population conservation included in the 2005 Wild Salmon Policy for Canada (DFO, ; Holt, Cass, Holtby, & Riddell, ). Infectious agents, as potential biological stressors, can lead to a continuum of health effects and sublethal impacts: deformity, clinical disease events and mortality (Stephen & Thorburn, ). However, monitoring‐sourced information has not been continuously and systematically collected to provide consistent evidence of infectious agent dynamics in wild salmonids in this region (Stephen et al, ).…”

Antibody response of two populations of common carp, Cyprinus carpio L., exposed to koi herpesvirus

“…Serological tests are commonly used in animal production systems but are not routinely used in aquaculture surveillance programmes. However, several studies indicate that specific anti‐viral antibodies are produced by a large proportion of fish in the virus‐exposed population, and these antibodies are detectable for long periods (Hill 1977; Hattenburger‐Baudouy, Danton, Merle, Torchy & de Kinkelin 1989; Dixon, Hattenberger‐Baudouy & Way 1994; Hattenburger‐Baudouy, Danton, Merle & de Kinkelin 1995; Crawford, Gardner & Hedrick 1999; St‐Hilaire, Ribble, LaPatra, Chartrand & Kent 2001). Neutralizing serum antibodies to channel catfish virus (CCV), a fish herpesvirus distantly related to KHV (Waltzek, Kelley, Stone, Way, Hanson, Fukuda, Hirono, Aoki, Davison & Hedrick 2005), are demonstrable in channel catfish for up to at least 6 months post‐exposure (Hedrick, Groff & McDowell 1987).…”