Part A | 4.7
40 Part A Marine Flora and Fauna
Additionally, phages could be the ideal strain for cotherapy along with antibiotics to prevent the emergence
of bacterial resistance to antibiotics. Especially lytic
phages are the most suitable candidates for phage
therapy, due to the fact that they reproduce rapidly
within the bacteria and lyse these in their specific host
range [4.29].
Since 2006, the United States Food and Drug Administration and United States Department of Agriculture have approved several bacteriophage products for
use on all food products. In marine aquaculture, the use
of bacteriophages for the control of bacterial diseases
in prawns in Asia has been considered. Phage therapy
has been applied to control the bacterial pathogen Vibrio harveyi, which causes luminous bacterial disease in
shrimp larvae [4.30]. Due to their host specificity, this
phage therapy may be applicable to control many bacterial diseases in the future.
4.6 Impact of Marine Viruses on Mollusks
Mollusks are invertebrates and one of the largest marine phyla. These bivalve mollusks are filter feeders,
thus marine viruses can be easily accumulated in their
tissues and may transfer or infect other species, including higher vertebrates and humans, through the
food chain. Although the pathogenic viruses are harmful to other species, it gives serious effect on the
bivalve mollusks [4.31]. In the 1960s a major epizootic gill necrosis was observed in the oyster Crassostrea angulata, and the first report of viral disease
in mollusks was reported at the same time. Most
mollusks are associated with many different types of
viruses including Herpesviridae, Papovaviridae, Togaviridae, Retroviridae, Reoviridae, Birnaviridae, Picornaviridae, and the irido-like virus [4.32]. Marine
molluscan viruses and their structure morphology and
main hosts are given in Table 4.2. Although many
viruses are associated with marine mollusks, herpeslike and birnavirus groups are the major threats to
mollusks.
4.6.1 Herpesvirus
Herpes-like virus infections have been identified in various marine mollusks throughout the world. As a result
of viral disease, European oyster fisheries were destroyed in the 1970s. Since the first observation of
the herpesvirus in Crassostrea virginica, many reports
suggest that mortality is associated with this virus in
Ostreaedulis and C. gigas in France and New Zealand.
Herpes-like viruses were also observed in haemocytes
of O. angasi adults in Australia and in New Zealand
in flat oysters, Tiostreachilensi. Ostreid herpesvirus 1
(OsHV1); a herpesvirus has been isolated and reported
from several species of bivalve mollusks. Moreover,
unlike most herpesviruses, this virus has a wide host
range of marine bivalves [4.32]. Sequence analysis
results have revealed that it has links with groups
of herpesviruses isolated from mammals, birds, and
fish [4.33].
4.6.2 Birnavirus
Marine birnaviruses (MABV) are icosahedral, nonenveloped viruses, belonging to Birnaviridae. The
genome of this virus comprises 2 segments of doublestranded RNA designated A and B [4.34]. MABVs
had been responsible for the considerable losses in
Pictada fucata, a commercially important pearl oyster in Japan [4.35]. MABVs infect a wide range of
shellfish and fish, and it has been suspected that
the mode of transmission may be due to zooplankton [4.36].
Viral diseases in bivalves are a serious concern
without any specific chemotherapies and vaccination.
According to the bivalve culture, a routine effective diagnostic tool is needed to monitor virus infection, and
it is also important to control viral diseases.
4.7 Marine Viruses and Shrimp Aquaculture
Shrimp comprise a main aquaculture commodity worldwide. Many viruses affect shrimps, causing severe
mortality of economically important shrimp species.
Approximately 60% of disease losses in shrimp aquaculture is associated with viral pathogens, 20% of
bacteria, and 20% by fungi and other pathogens [4.37].
40 Part A Marine Flora and Fauna
Additionally, phages could be the ideal strain for cotherapy along with antibiotics to prevent the emergence
of bacterial resistance to antibiotics. Especially lytic
phages are the most suitable candidates for phage
therapy, due to the fact that they reproduce rapidly
within the bacteria and lyse these in their specific host
range [4.29].
Since 2006, the United States Food and Drug Administration and United States Department of Agriculture have approved several bacteriophage products for
use on all food products. In marine aquaculture, the use
of bacteriophages for the control of bacterial diseases
in prawns in Asia has been considered. Phage therapy
has been applied to control the bacterial pathogen Vibrio harveyi, which causes luminous bacterial disease in
shrimp larvae [4.30]. Due to their host specificity, this
phage therapy may be applicable to control many bacterial diseases in the future.
4.6 Impact of Marine Viruses on Mollusks
Mollusks are invertebrates and one of the largest marine phyla. These bivalve mollusks are filter feeders,
thus marine viruses can be easily accumulated in their
tissues and may transfer or infect other species, including higher vertebrates and humans, through the
food chain. Although the pathogenic viruses are harmful to other species, it gives serious effect on the
bivalve mollusks [4.31]. In the 1960s a major epizootic gill necrosis was observed in the oyster Crassostrea angulata, and the first report of viral disease
in mollusks was reported at the same time. Most
mollusks are associated with many different types of
viruses including Herpesviridae, Papovaviridae, Togaviridae, Retroviridae, Reoviridae, Birnaviridae, Picornaviridae, and the irido-like virus [4.32]. Marine
molluscan viruses and their structure morphology and
main hosts are given in Table 4.2. Although many
viruses are associated with marine mollusks, herpeslike and birnavirus groups are the major threats to
mollusks.
4.6.1 Herpesvirus
Herpes-like virus infections have been identified in various marine mollusks throughout the world. As a result
of viral disease, European oyster fisheries were destroyed in the 1970s. Since the first observation of
the herpesvirus in Crassostrea virginica, many reports
suggest that mortality is associated with this virus in
Ostreaedulis and C. gigas in France and New Zealand.
Herpes-like viruses were also observed in haemocytes
of O. angasi adults in Australia and in New Zealand
in flat oysters, Tiostreachilensi. Ostreid herpesvirus 1
(OsHV1); a herpesvirus has been isolated and reported
from several species of bivalve mollusks. Moreover,
unlike most herpesviruses, this virus has a wide host
range of marine bivalves [4.32]. Sequence analysis
results have revealed that it has links with groups
of herpesviruses isolated from mammals, birds, and
fish [4.33].
4.6.2 Birnavirus
Marine birnaviruses (MABV) are icosahedral, nonenveloped viruses, belonging to Birnaviridae. The
genome of this virus comprises 2 segments of doublestranded RNA designated A and B [4.34]. MABVs
had been responsible for the considerable losses in
Pictada fucata, a commercially important pearl oyster in Japan [4.35]. MABVs infect a wide range of
shellfish and fish, and it has been suspected that
the mode of transmission may be due to zooplankton [4.36].
Viral diseases in bivalves are a serious concern
without any specific chemotherapies and vaccination.
According to the bivalve culture, a routine effective diagnostic tool is needed to monitor virus infection, and
it is also important to control viral diseases.
4.7 Marine Viruses and Shrimp Aquaculture
Shrimp comprise a main aquaculture commodity worldwide. Many viruses affect shrimps, causing severe
mortality of economically important shrimp species.
Approximately 60% of disease losses in shrimp aquaculture is associated with viral pathogens, 20% of
bacteria, and 20% by fungi and other pathogens [4.37].