Fish disease and health management

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Fish Disease and Health Management
Introduction:
Aquaculture in Bangladesh is growing rapidly with respect to both quantity and
variety of species. Bangladesh ranked 5th position in leading aquaculture producing
countries in the world just after China, India, Vietnam and Indonesia (FAO, 2013).
Bangladesh produced 30,61,687 mt fish in 2011 of which 15,23,759 mt i.e. 49.76%
was produced by the aquaculture sector. Bangladesh contributed 2.43% in world total
aquaculture production in 2011. Pond culture represents the mainstay of aquaculture
in Bangladesh, accounting for 85.8% of the total recorded production and 57.7% of
the area under culture (DOF, 2010).
The current trend in aquaculture development is towards increased intensification and
commercialization of aquatic production. Like other farming sectors, the likelihood of
major disease problems increases as aquaculture activities intensify and expand.
Disease is considered as a primary constraint to the culture of many aquatic species,
impeding both economic and social development in many countries. A number of
diseases like epizootic ulcerative syndrome, skin erosion, gill damage, tail and fin rot
are common in farmed fishes of Bangladesh. In pond aquaculture system, high
stocking density and irregularly feed supply is very prone to disease outbreak. Most
pond fish farmers do not have a good understanding of health and disease issues in
their system. Many diseases of fish are secondary to environmental insult, and can be
prevented through proper management. (FAO, 2013).
Types of Fish Disease
Fish ailments can be separated into 4 general types including bacterial infections,
fungal infections, parasitic or protozoan infections, and physical ailments and wounds.
Bacterial Diseases: Bacterial diseases are usually characterized by red streaks or
spots and/or swelling of the abdomen or eye. These are best treated by antibiotics such
as penicillin, amoxicillin, or erythromycin.
Fungal Diseases: Common fungal infections often look like gray or white fluffy
patches.
Parasitic Diseases: The most common parasitic disease called "Ich" can be treated
most effectively with copper or malachite green in the right dosage. Most treatments
will have copper as an ingredient. Many water treatments like "Aquari-Sol" will also
contain copper as an ingredient. If the treatment you use is an anti-biotic or copper
based, remember to remove all carbon from the filtration system.

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Physical Ailments: Physical Ailments are often the result of the environment. Poor
quality water conditions can lead to fish gasping, not eating, jumping out of the tank,
and more. Tank mate problems can result in nipped fins and bite wounds.
Table: Types of Fish Disease
Bacterial Parasitic Protozoan
 Fin Rot
 Pop-Eye
 Cloudy Eye
 External Infections
 Fish TB
 Dropsy
 Septicemia
 Swim Bladder
Disease
 Enteric Red Mouth
 Argulus
 Anchor Worm
 Black Spot -
Black Ick
 Ergasilus
 Flukes
 Nematoda
 Leeches
 Uronema
marinum
 Velvet or Rust
 Marine Velvet
 Brooklynella/Clownfish
Disease
 Costia
 Hexamita
 Ich - White Spot
 Marine Ich -
Crypt/Marine White
Spot
 Neon Tetra Disease
 Glugea and Henneguya
 Chilodonella
 Fungal
 Fungus
 Ichthyosporidium
Non-infectious Viral Miscellaneous
 Tumors
 Congenital
Abnormalities
 Injuries
 Constipation
 Herpesvirus
disease
 Epithelioma
papillosum (Fish
Pox)
 Infectious
Hematopoietic
Necrosis (IHN)
 Viral
Hemorrhagic
septicemia
 Spring Viremia of
Carp (SVC) and
 Swim Bladder
Infection virus
(SBI)
 Head and Lateral Line
Erosion
'Hole-in-the-head'
Disease
 Eye Problems
 Swim-bladder Disease
Health as a constraint to aquaculture:
The current trend in aquaculture development is towards increased intensification and
commercialization of aquatic production. Like other farming sectors, the likelihood of

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major disease problems occurring increases as aquaculture activities intensify and
expand. Thus, the aquaculture industry has been overwhelmed with its share of
diseases and problems caused by viruses, bacteria, fungi, parasites and other
undiagnosed and emerging pathogens. Disease is now a primary constraint to the
culture of many aquatic species, impeding both economic and social development in
many countries. This situation can be attributed to a variety of multi-faceted and
highly interconnected factors such as the increased globalization of trade in live
aquatic animals and their products; the intensification of aquaculture through the
translocation of brood stock, post larvae, fry and fingerlings; the development and
expansion of the ornamental fish trade; the enhancement of marine and coastal areas
through stocking aquatic animals raised in hatcheries; the misunderstanding and
misuse of specific pathogen free (SPF) stocks (e.g. shrimps); unanticipated negative
interactions between cultured and wild fish populations; poor or lack of effective
biosecurity measures; slow awareness on emerging diseases; climate change; all other
human mediated movements of aquaculture commodities.
However, once a pathogen or disease agent is introduced and becomes established into
the natural environment, there is little or no possibility for either treatment or
eradication. While consequences of "trickle" infections from wild to cultured
populations have predictable consequences due to accessible hosts under cultured
conditions, the consequences of culture-borne transmission to wild stocks are harder
to predict.
Fish Health management:
This requirement recognizes two related aspects of the fish health management as it
applies to aquaculture operations, these being that:
 Trans-boundary movement of fry, fingerlings and market size fish should be
conducted in ways that minimize risk of spread of fish pathogens; and
 Aquaculture farms should adopt effective farm and fish health management
practices favoring hygienic measures and vaccines.
Trans-boundary diseases are highly contagious and can spread rapidly across national
borders, causing serious socio-economic and public health consequences. The
expanding trade in grouper seed for grow-out for the Live Reef Food Fish Trade will,
without proper quarantine and health measures, increase risks of pathogen spread. The
FAO Technical Guidelines on Aquaculture Development states that transfers of eggs,
fingerlings and adults among river basins or large water bodies should be avoided.
Introduced species are often preferred because they attract higher prices and have
greater export potential.

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Where possible, Governments should assist in ensuring grouper seed and broodstock
are sold free of disease by:
 Requiring a breeding and disease history be maintained for broodstock and
seed that is be transferred within the country or exported. Where possible, only
eggs or seed that are certified as specific pathogen free should be used
(including those supplied to backyard nurseries);
 Requiring the use of approved chemicals and drug use prior to and during
transport of seed and marketable fish and
 Developing guidelines on certifying seed for trans-boundary movements.
Most disease outbreaks occur during the first 2 - 12 weeks after initial placement in
the grow-out cages. And depends on the condition of the fish on arrival, their size and
fish species involved. Regular monitoring of the health of cultured grouper is
important for effective prevention of diseases caused by infectious micro-organisms or
stress, and early detection of health problems. The main areas for consideration that
will facilitate the prevention and containment of diseases include:
 Poor handling and transportation techniques that induce stress, lower water
quality and cause external injuries;
 Disease transmission in transportation through contaminated water;
 Disease transmission caused by farming multiple species that come from
various locations in close proximity and by regularly exposing newly
introduced juveniles to existing pathogens in the cages;
 Poor feed handling and storage of trash fish or artificial feeds
The socio-economic impacts of higher costs imposed on small-scale aquaculture
nursery operators in adopting disease prevention and treatment programs should be
considered in terms of higher benefits. Governments, non-government organizations
and regional agencies should facilitate extension, outreach and technical support
activities that raise awareness of farmers and aquaculture operations on health
management issues including:
 Technical training to farm managers and workers on the surveillance,
monitoring and early detection of disease in fish and the course of action to be
taken once diseased fish are identified;
 The availability of diagnostic services to identify those pathogens already
present in the culture environment and the methods for sending specimens for
diagnosis; and
 Common diseases in grouper species and their prevention and treatment.

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Routine disease prevention or prophylactic treatment should be incorporated into both
the transport and packing of grouper seeds the farm management activities for newly
arrived seed/fish. The main principles of disease treatment and control are to:
 Establish an accurate diagnosis;
 Select the appropriate environmentally responsible treatment; and
 Evaluate management practices and identify areas critical to the prevention of
future outbreaks.
Any chemicals or drugs used should be acceptable in terms of risk to human health or
the environment and to end markets, should be easily available and importantly, their
correct use must be understood.
Responsible Practice:
 Controlling trans-boundary movements. Trans-boundary movements of fry,
fingerlings and market size fish should be conducted in ways that minimize risk
of spread of fish pathogens
 Utilize existing international codes of practice. Existing international codes
of practice that address trans-boundary movement and use of introduced
species in aquaculture should be used as a framework to develop codes relevant
to tropical latitudes and species. Existing databases should be used to identify
and determine risks from imported species.
 Recording breeding and disease history. Breeding history and disease history
should be maintained for aquaculture stocks to facilitate exchange of disease
free brood stock and seed both within the country and for export.
 Farms should ensure fish are sold free from disease. Aquaculture farm
should use eggs or seed that are certified as specific pathogen free (including
eggs supplied to backyard nurseries)
 Accessing fish health management advice. Governments, non-government
organizations and regional agencies should facilitate extension, outreach and
technical support activities that raise awareness of farmers and aquaculture
operations on health management issues including technical training,
diagnostic services and disease prevention and treatment.
Adopting farm and fish health management practices:
 Fishers, exporters and farms shall adopt effective fish health management
practices for the prevention and containment of diseases by:

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 Reducing stress potential for injury during handling and
transportation,
 Minimizing the potential for disease transmission among
different cohorts and species; and
 Implementing good handling and storage practices for trash fish
and artificial feeds
 Aquaculture farms shall adopt effective prophylactic treatment programs for
the prevention, treatment and control of disease through:
 Establishing effective and accurate diagnosis procedures,
 Selecting the treatments that meet acceptable environmental and
human health risks; and
 Evaluating management practices and identifying critical
prevention areas
 Recognize socio-economic impacts: The socio-economic impacts of higher
costs from adopting disease prevention and treatment programs should be
offset against potential higher benefits
Good Farming Health Management Practices:
A health management program has several requirements and must cover all levels of
aquaculture activity. At the production level, the requirements for a healthy
environment include strong healthy seed and juveniles, proper nutrition, appropriate
waste management, optimal water quality, and regular monitoring. At the farm site
level, good record keeping is essential. It should cover all aspects of farm operation.
Farmers should be trained to understand the importance and value of such information
in determining the course or nature of a disease outbreak, providing accurate and rapid
diagnosis, and enabling sensible management decisions for intervention and control.
Record keeping is crucial to aquaculture and can go a long way in supporting effective
health and productivity management efforts.
A good farm profile should contain the following information:
 Treatment administered;
 Clinical signs (behavior, appearance);
 Farm lay-out (inflow, outflow, connection of ponds);

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 Animals cultured (species, numbers, origin, age classes);
 Yields (per pond, per cage, per farm, normal survival rates);
 Nutrition (live food, manufactured food, sources, feeding practices);
 Management practices (continuous stocking, closed operation, stocking
densities);
 Mortality data (affected sites, cages, ponds along with approximate percentages
and numbers); and
 Unusual events (abnormal weather changes, mortality above average, yield
below average, land-use activity, run-off, spills, abnormal growth, spawning
events).
In addition to regular record keeping, there should be a continuous monitoring and
updating of information (new animals on farm, change of feed, new ponds connected,
and new farms upstream).
Economic investments and opportunities in aquatic animal health:
Economic impacts have also been expressed in terms of costs of investment in disease
research and control and health management programmes. so far no systematic
economic assessment has been carried out. In the foreseeable future, there will be
increasing demand for such assessments in order to gain attention and continuous
support from both the public and private sectors.
Conclusion:
Aquaculture activities in Bangladesh are predominantly pond based. Addressing
health questions with both pro-active and reactive programs has become a primary
requirement for sustaining aquaculture production and product trade. The current
strategy in the Asia-Pacific region emphasizes responsible health management to
minimize the risks of disease incursions brought about by the movement of live
aquatic animals and their products. The risk of major disease incursions and newly
emerging diseases will keep on threatening the sector, and unless appropriate health
management measures are maintained and effectively implemented, the government
and private sectors will be faced with more costs in terms of production losses and the
efforts needed to contain and eradicate diseases, funds that would have been better
spent in preventing their entry into the system. Focusing efforts on prevention, on
better management practices and on maintaining healthy fish maybe more important
than focusing on why fish get sick. Health management is a shared responsibility, and
each stakeholder's contribution is essential to the health management process.

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