Vaccines

Several vaccines for IHNV have been developed and the relative merits of these vaccines have been discussed (Leong et al., 1988, 1997 Winton, 1991 Leong, 1993 Leong and Fryer, 1993). There are five basic formulations used in vaccine development live attenuated vaccines, whole inactivated vaccines, purified subunits (proteins or glycoproteins) of the pathogen, purified proteins from cloned genes and DNA vaccines. These formulations have had some success against IHNV in the laboratory, but a...

Humoral immune response to infectious haematopoietic necrosis virus

Amend and Smith (1974) showed that fish hyperimmunized with IHNV mounted a humoral immune response, with the production of neutralizing antibodies. It was later shown that viral neutralization by antibodies was complement-dependent (Hattenberger-Baudouy et al, 1989). The humoral immune responses to IHNV and other fish viruses are very similar. Young rainbow trout during an IHN epizootic did not have detectable neutralizing antibody titres, but by 4.5-6 months after infection, when the virus was...

Factors affecting transmission and virulence

Fish typically become more resistant to IHNV as they increase in age and weight (Amend, 1974 Amend and Nelson, 1977 Leong and Turner, 1979 Wolf, 1988 LaPatra et al. 1994a). Yolk-sac fry and fish up to 2 months of age are highly susceptible, with mortality often over 90 . Older fish up to 6 months of age typically have less than 50 mortality. After experimental IHNV exposures, fry mortality generally increases as the viral dose increases from 102 to 105-6 pfu ml- (Chen et al., 1990 LaPatra et...

Staphylococcal coagglutination

Staphylococcal coagglutination can specifically detect and identify IHNV grown in cell cultures or in infected fish tissue Bootland and Leong, 1992 . This test is simple and, since it takes only 15 min, it is one of the most rapid methods of diagnosing IHNV. It has the added benefit of being suitable for field use, because it only requires a light microscope, glass slides and one reagent. The test uses formalin-fixed Staphylococcus aureus cells sensitized with unadsorbed polyclonal rabbit...

Host range

During the last 10 years, IHNV has been isolated from several new fish species, and the host range of the virus has enlarged. Initially, the host range of IHNV was thought to be limited to the genus Oncorhynchus Table 2.1 . Infectious haematopoietic necrosis is often reported in rainbow trout, in steelhead trout and in the Pacific salmon - sockeye, kokanee, chinook and chum salmon Wolf, 1988 . Cutthroat trout are also susceptible to IHNV infection and disease Parisot, 1962 Groberg, 1983 ....

Control And Treatment Transmission and pathogenesis

Ihnv Growth Cycle

The epizootiology of IHNV is not completely understood and the source of virus infecting salmonids is still unknown. However, survival of IHNV in a fish population depends on a close association of the virus with the life cycle of the fish host Fig. 2.5 . Similarly to other salmonid viruses, IHNV typically causes an acute disease in young salmon and trout. Mortalities of fry and fingerlings can be as high as 90 , but occasional epizootics have been reported in smolts and older fish Yasutake,...

Identification of infectious haematopoietic necrosis virus by nonserological methods

In most of the above serological methods of diagnosing IHNV, the virus must be amplified in cell culture until protein antigen concentrations reach detectable levels. Instead of detecting antigens, it is possible to detect viral particles by electron microscopy EM . Nucleic acids can be detected using the polymerase chain reaction PCR and nucleic acid probes. Since viral mRNA is synthesized before proteins in infected cells, detection of viral RNA may result in an earlier diagnosis of IHNV....