Effectiveness of a vaccine against red sea bream iridoviral disease in a field trial test

[Red sea bream iridoviral disease]

The first outbreak of red sea bream iridoviral disease caused by red sea bream iridovirus (RSIV) was recorded in cultured red sea bream Pagrus major in Shikoku Island, Japan in 1990. Since 1991, the disease has caused mass mortalities of cultured marine fishes not only red sea bream but also many other species. The affected fish were lethargic and exhibited severe anemia, petechiae of the gills, and enlargement of the spleen. The causative agent was a large, icosahedral, cytoplasmic DNA virus classified as a member of the family Iridoviridae and was designated as red sea bream iridovirus (RSIV). The genome of RSIV is liner dsDNA and considered to be circularly permitted and terminally redundant like other iridoviruses. The length of physical map of RSIV genome is 112,415bp. An indirect immunofluorescence test with a monoclonal antibody and PCR are commonly used for the rapid diagnosis of RSIV infected fish in the field. For the control of this disease, a formalin-killed vaccine against red sea bream iridoviral disease was developed and now commercially available.

Amphibian virology

Amphibians are a diverse group of species; much work remains to be done to elucidate the viruses of amphibians. Viral diseases may play an important role in wild and captive amphibian populations. Iridoviruses are a leading cause of wild amphibian mortality events in the United States and are a common cause of amphibian mortality events worldwide. In addition to frank viral diseases, viral infections may play a role in the establishment of bacterial, fungal, and parasitic diseases and are an underlying cause of neoplasia. It is important for the amphibian clinician to recognize disease syndromes and pathology that are consistent with viral etiology.

Morphological changes contribute to apoptotic cell death and are affected by caspase-3 and caspase-6 inhibitors during red sea bream iridovirus permissive replication

Red sea bream iridovirus (RSIV) of the Iridoviridae family is a causative agent of lethal infections in many cultured marine fish species in southwestern Japan. RSIV-induced apoptosis was divided as follows: (1). cell shrinkage and rounding at the early apoptotic stage, (2). cell enlargement at the middle apoptotic stage, (3). formation of apoptotic body-like vesicles at the late apoptotic stage and phagocytosis by neighboring cells, and (4). loss of membrane integrity in apoptotic body-like vesicles without phagocytosis by neighboring cells. By affinity labeling, RSIV-induced apoptosis included caspase-dependent apoptosis. RSIV infection caused cell rounding but not cell enlargement or formation of apoptotic body-like vesicles and further restricted part of the structural protein synthesis in the presence of caspase-3 and -6 inhibitors. These findings showed the involvement of caspase-3 and -6 in the morphological changes at the middle and late apoptotic stages and viral protein synthesis in the late stage of RSIV infection.

Diseases of tunas, Thunnus spp

Much is known about those aspects of tuna health which can be studied in wild populations, e.g. helminth parasites. However, because aquaculture of these species is in its infancy, knowledge of microbial, nutritional and environmental diseases is limited. This review is an attempt to bring together the available information on those diseases of Thunnus spp. which cause significant morbidity, mortality or economic loss. In doing so it has become clear that much more research needs to be undertaken on the physiology of the species (southern, northern and Pacific bluefin tuna) currently used in aquaculture in order for the pathogenesis of some conditions to be properly understood. Attempts at hatchery culture of Pacific bluefin tuna has indicated that Thunnus spp. will be problematic to hatch and propagate.

Viruses of lower vertebrates

Viruses of lower vertebrates recently became a field of interest to the public due to increasing epizootics and economic losses of poikilothermic animals. These were reported worldwide from both wildlife and collections of aquatic poikilothermic animals. Several RNA and DNA viruses infecting fish, amphibians and reptiles have been studied intensively during the last 20 years. Many of these viruses induce diseases resulting in important economic losses of lower vertebrates, especially in fish aquaculture. In addition, some of the DNA viruses seem to be emerging pathogens involved in the worldwide decline in wildlife. Irido-, herpes- and polyomavirus infections may be involved in the reduction in the numbers of endangered amphibian and reptile species. In this context the knowledge of several important RNA viruses such as orthomyxo-, paramyxo-, rhabdo-, retro-, corona-, calici-, toga-, picorna-, noda-, reo- and birnaviruses, and DNA viruses such as parvo-, irido-, herpes-, adeno-, polyoma- and poxviruses, is described in this review.