VIRUSES IN THE AQUASYTEM :

“FISHERIES”The Fishing Industry

BUSINESS

FOOD SOURCE

TRADE and TOURISM

RECALL:

A VIRUS is a particle whose genome is nucleic acid either DNA or RNA that

reproduces inside a living cell

All Viruses are Obligate Pathogens

AN ADVANTAGE;

THE BACTERIOPHAGE A common and diverse group of

viruses and are the most abundant form of biological entity in aquatic environments.

Bacteriophages are the viruses which infects bacteria which are widely distributed in nature and found in water, in soil, in humans or in the cell of microbes.

Bacteriophages like all viruses are composed of nucleic acid surrounded by a protein coat.

TWO TYPES OF BACTERIAL VIRUSES

i). Lytic or virulent phages: -        These phages infect the bacteria and the cells respond by producing large number of virus by lysing or killing the bacterial cells.

ii. Lysogen phages: -             These phages incorporate their genome into the host genome and divide along with the host bacterial cells and no cell lyses occurs in this type of phages.

Use in Aquaculture:

 Advantages of Bacteriophages over Antibiotics:

AQUA-CULTURE

ANTI-BIOTICS

TREAT/ ControlBACt.

DIseases

Longterm exposure

Antibiotic Resistant strains of bacteria in

aqua environment

Disease OUTBREAK

Economical LOST of Fish

Farmers

Bacteriophagein AQUACULTURE

(Resangpan and Kitao, 1992 and Karunasagar, et al., 1994).

Advantages of Bacteriophages over Antibiotics:

The used of phages for the biological control of pathogens of cultured fish and shrimp has developed interest in recent years since no drugs residues, drug toxicity are associated with this type of therapy

(Wu and choa,1981; Nakai et al ., 1999.)

OTHER ADVANTAGES of VIRUSES

• BALANCE in the food webs.

(e.g bacteria – virus relationship)

• Marine viruses add a whole new dimension to EVOLUTION.

THE DISADVANTAGES

CAUSES OF FISH DISEASES

Determinants of Viral Pathology

Once the virus enters the cell, it may either 1)cause no major change in the cell;2) kill the cell; or 3) cause the cell to multiply rapidly and

then die or become cancerous.

Patterns of Disease

THREE major patterns of disease

(1) localized

(2) disseminated

(3) unapparent.

caused by viruses which first spread sequentially throughout various regions and organs of the body, often spreading via the blood (called a viremia), and then cause disease

infection patterns that tend to stay in or near the site or organ of infection

the most common.

VIRAL FISH DISEASES

The Disadvantage:

Fish Pox A.K.A. cutaneous warts/Epithelioma papulosum/ carp pox.

causes growth retardation, mortality and some spinal deformation.

Temperature correlated disease- occurs during cooler months and disappears at warmer months.

Viral haemorrhagic septicemia (VHS) 

A.K.A. “Egtved disease”/ “Egtved virus” (VHSV)

• Different strains of VHSV occur in different regions and affect different species.

• Virus not known to be harmful to human

Spring Viremia of Carp, SVC

• A.K.A. Acute Infectious Dropsy.

• Caused by Rhabdovirus carpio.

• Respiration/ gilling reduced, loss of equilibrium and some stay near the bottom.

• Affected fish have dropsy(swollen abdomen) blood spots on skin,gills and eyes, intestinal infection evident.

RECENT STUDIES

Fish Virology

virology

• - a member the orthomyxoviruses and makes up the genus Isavirus

• - has a genome consisting of eight single strand negative sense RNA segments of equivalent size range

Infectious salmon anemia virus (ISAV)

• - belongs to the genus alphavirus in the family Togaviridae

• - the causative agent of the economically important disease known as Pancreas Disease (PD)

• - genome molecule is in itself infective to a host cell if it is introduced to cytosol

Salmonid alphavirus (SAV)

• associated with heart and skeletal muscle inflammation (HSMI)

• almost ubiquitous among farmed fish

Piscine reovirus (PRV)

END