Marine Viruse
35
Part A | 4.1
4. Marine Viruses
Jeeva Subbiah
Marine viruses are the most abundant life-forms
in the ocean and exist wherever life is found. The
estimated virus count in the ocean is 10
30 , and
every second about 10
23 viral infections occur in
the ocean. These infections are a major source of
disease and mortality in organisms ranging from
shrimp to whales. Each infection potentially introduces new genetic information into an organism
or into progeny viruses. These new genetic changes
allow evolution of the host and virus population.
Viruses represent the planet’s largest pool of genetic diversity. Our understanding of the impact of
viruses on global systems, however, is still incomplete. This chapter will present a general review
of marine viruses; their impact on marine organisms, such as cyanobacteria, mollusks, and more
detailed about shrimp viruses, diagnostics and the
control of shrimp viral diseases.
4.1 Viruses ................................................... 35
4.2 General Characteristic Features of Viruses . 36
4.3 Host Specificity ....................................... 36
4.4 Viral Families in Marine Ecosystems.......... 36
4.5 Marine Phages ........................................ 37
4.5.1 Types of Phage Infection ................. 37
4.5.2 Cyanophages ................................. 38
4.5.3 Phage Therapy ............................... 39
4.6 Impact of Marine Viruses on Mollusks ...... 40
4.6.1 Herpesvirus ................................... 40
4.6.2 Birnavirus ..................................... 40
4.7 Marine Viruses and Shrimp Aquaculture ... 40
4.7.1 RNA Viruses in Shrimp .................... 41
4.7.2 DNA Viruses of Shrimp .................... 41
4.7.3 White Spot Syndrome Virus (WSSV) ... 41
4.7.4 Shrimp Parvoviruses ....................... 42
4.7.5 Diagnostic Methods
for Shrimp Virus Diseases ................ 43
4.7.6 Factors Responsible
for Shrimp Viral Diseases................. 45
4.7.7 Control of Shrimp Viral Disease ........ 45
4.8 Conclusion .............................................. 46
References..................................................... 47
4.1 Viruses
Viruses are more common in air, soil, and water, including the ocean environment, and exist wherever
life is found. They are obligate intracellular parasites
and infect all living organisms such as vertebrates,
invertebrates, plants, fungi, algae, archaea, and bacteria. The marine environment is the major habitat for
many living organisms which have a large virus population, and the interaction between virus and their
hosts allow the evolution of both viruses and host organisms. Furthermore, each and every progeny virus
has the potential to evolve as a new virus, which
may involve a huge impact on living organisms or become an emerging virus [4.1]. The evolved new viral
strains change in virulence and transfer viruses between
ecosystems. In some circumstances, gene transformation between viruses and their hosts may produce
dramatic effects on the hosts. For example, the wellknown phage cholera toxin (CTX) gene originated
from CTXf or CTX' bacteriophage through horizontal
gene transfer. The bacterium Vibrio cholera is normally
harmless but could become one of humanity’s greatest
scourges by incorporating CTX genes of filamentous
phage (Inovirus) from the family Inoviridae [4.2, 3].
Marine viruses are not only the major cause of mortality in marine organisms but are also involved in
global biogeochemical cycle changes. Moreover, they
are a huge reservoir of the greatest genetic diversity
on Earth. The estimated virus count in the ocean is
35
Part A | 4.1
4. Marine Viruses
Jeeva Subbiah
Marine viruses are the most abundant life-forms
in the ocean and exist wherever life is found. The
estimated virus count in the ocean is 10
30 , and
every second about 10
23 viral infections occur in
the ocean. These infections are a major source of
disease and mortality in organisms ranging from
shrimp to whales. Each infection potentially introduces new genetic information into an organism
or into progeny viruses. These new genetic changes
allow evolution of the host and virus population.
Viruses represent the planet’s largest pool of genetic diversity. Our understanding of the impact of
viruses on global systems, however, is still incomplete. This chapter will present a general review
of marine viruses; their impact on marine organisms, such as cyanobacteria, mollusks, and more
detailed about shrimp viruses, diagnostics and the
control of shrimp viral diseases.
4.1 Viruses ................................................... 35
4.2 General Characteristic Features of Viruses . 36
4.3 Host Specificity ....................................... 36
4.4 Viral Families in Marine Ecosystems.......... 36
4.5 Marine Phages ........................................ 37
4.5.1 Types of Phage Infection ................. 37
4.5.2 Cyanophages ................................. 38
4.5.3 Phage Therapy ............................... 39
4.6 Impact of Marine Viruses on Mollusks ...... 40
4.6.1 Herpesvirus ................................... 40
4.6.2 Birnavirus ..................................... 40
4.7 Marine Viruses and Shrimp Aquaculture ... 40
4.7.1 RNA Viruses in Shrimp .................... 41
4.7.2 DNA Viruses of Shrimp .................... 41
4.7.3 White Spot Syndrome Virus (WSSV) ... 41
4.7.4 Shrimp Parvoviruses ....................... 42
4.7.5 Diagnostic Methods
for Shrimp Virus Diseases ................ 43
4.7.6 Factors Responsible
for Shrimp Viral Diseases................. 45
4.7.7 Control of Shrimp Viral Disease ........ 45
4.8 Conclusion .............................................. 46
References..................................................... 47
4.1 Viruses
Viruses are more common in air, soil, and water, including the ocean environment, and exist wherever
life is found. They are obligate intracellular parasites
and infect all living organisms such as vertebrates,
invertebrates, plants, fungi, algae, archaea, and bacteria. The marine environment is the major habitat for
many living organisms which have a large virus population, and the interaction between virus and their
hosts allow the evolution of both viruses and host organisms. Furthermore, each and every progeny virus
has the potential to evolve as a new virus, which
may involve a huge impact on living organisms or become an emerging virus [4.1]. The evolved new viral
strains change in virulence and transfer viruses between
ecosystems. In some circumstances, gene transformation between viruses and their hosts may produce
dramatic effects on the hosts. For example, the wellknown phage cholera toxin (CTX) gene originated
from CTXf or CTX' bacteriophage through horizontal
gene transfer. The bacterium Vibrio cholera is normally
harmless but could become one of humanity’s greatest
scourges by incorporating CTX genes of filamentous
phage (Inovirus) from the family Inoviridae [4.2, 3].
Marine viruses are not only the major cause of mortality in marine organisms but are also involved in
global biogeochemical cycle changes. Moreover, they
are a huge reservoir of the greatest genetic diversity
on Earth. The estimated virus count in the ocean is