Age- and weight-dependent susceptibility of rainbow trout Oncorhynchus mykiss to isolates of infectious haematopoietic necrosis virus (IHNV) of varying virulence

Abstract

The virulence of 5 European and 1 North American isolate of infectious haematopoietic necrosis virus (IHNV) was compared by infecting female sibling rainbow trout ('Isle of Man' strain) of different weights and ages (2, 20 and 50 g). The fish were exposed to 10 4 TCID 50 IHNV per ml of water by immersion, and the mortality was recorded for 28 d. Two new IHNV isolates from Germany were included in the investigation. One was isolated from European eels kept at 23°C (± 2°C) and the other was not detectable by immunofluorescence with commercially available monoclonal antibodies recognising the viral G protein. The results showed that IHNV isolates of high or low virulence persisted in rainbow trout of all ages/weights for 28 d, with the exception of fish over 15 g in the eel IHNV (DF [diagnostic fish] 13/98)-infected groups from which the virus could not be reisolated on Day 28. The smallest fish were most susceptible to an infection with any of the IHNV isolates. The lowest cumulative mortality (18%) was observed in fingerlings infected with the North American isolate HAG (obtained from Hagerman Valley), and the highest mortality (100%) in DF 04/99 infected fish. The DF 04/99 and Ö-13/95 viruses caused mortality in fish independent of their weight or age. The isolates FR-32/87 and I-4008 were virulent in fish up to a weight of 20 g and caused no mortality in larger fish. In the IHNV HAG-and DF 13/98 (eel)-infected rainbow trout, no signs of disease were observed in fish weighing between 15 and 50 g. An age/weight related susceptibility of rainbow trout was demonstrated under the defined conditions for all IHNV isolates tested.

Attenuated Infectious Hematopoietic Necrosis Virus with Rearranged Gene Order as Potential Vaccine

“…Age-and weight-dependent susceptibility of rainbow trout (Oncorhynchus mykiss) to IHNV has been well documented (20). In the current study, N2G3 presented the best balance between attenuation and protection.…”

Viral diseases of wild and farmed European eel Anguilla anguilla with particular reference to the Netherlands

“…In 1998, an IHNV isolate, DF13/98, was isolated from diseased farmed Anguilla anguilla kept at 23°C in Germany (Bergmann et al 2003). Rainbow trout of various age and weight classes were infected with DF13/98 by immersion and reared for 28 d at 9°C.…”

“…The virus appeared to be highly pathogenic for intraperitoneally infected rainbow trout fry (3 mo old) at 13°C, with a cumulative mortality of 89%, but much less pathogenic for 5 mo old rainbow trout fingerlings, with a mortality of only 15%. The pathogenicity of the isolated virus for eel, as well as the origin of the elver contamination, remains unknown.In 1998, an IHNV isolate, DF13/98, was isolated from diseased farmed Anguilla anguilla kept at 23°C in Germany (Bergmann et al 2003). Rainbow trout of various age and weight classes were infected with DF13/98 by immersion and reared for 28 d at 9°C.…”

Effect of age on liver pathology and other diseases in flatfish: implications for assessment of marine ecological health status

“…Numerous studies have demonstrated differential susceptibility between age cohorts of the same host species, normally in the context of aquaculture, whereby early age classes (such as eggs and larvae) can be afflicted by different diseases (or the same diseases at a different prevalence and severity) to those observed in adult life stages (e.g. Kiran et al 2002, Bergmann et al 2003. This concept provides a rationale to consider whether similar phenomena may be apparent in natural (wild) populations of aquatic animals and furthermore, whether differential age of onset for the same disease may occur across geographical regions or temporally.…”