Fish Diseases: Velvet Disease & Dropsy

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BARKATULLAH UNIVERSITY
BHOPAL
DEPARTMENT OF ZOOLOGY & APPLIED
AQUACULTURE
FISH DISEASES
Microbial , Parasitic & Fungal Diseases Of Fish And
Shellfish
SUBMITTED BY SUBMITTED TO
SHUBHAM PATIDAR Miss- ANUBHUTI MINNARE
M.F.Sc. - 2ND
Sem

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(1)VelvetRust Disease
 Velvet disease (also called gold-dust, rust and coral disease) is a fish disease caused by
dinoflagellate parasites of the genus Piscinoodinium, specifically Amyloodinium in
marine fish, and Oodinium in freshwater fish. The disease gives infected organisms a
dusty, brownish-gold color. The disease occurs most commonly in tropical fish, and to a
lesser extent, marine aquaria.
Etiology
 Velvet is caused by a small parasite known as Oodinium which can latch onto the body,
gills and fins of fish. It is sometimes also referred to as rust disease or gold dust disease.
... Certain conditions may also put fish at higher risk of velvet due to stress.
Life Cycle
 The single-celled parasite's life cycle can be divided into three major phases. First, as a
tomont, the parasite rests at the water's floor and divides into as many as 256 tomites.
Second, these juvenile, motile tomites swim about in search of a fish host, meanwhile
using photosynthesis to grow, and to fuel their search. Finally, the adolescent tomite finds
and enters the slime coat of a host fish, dissolving and consuming the host's cells, and
needing only three days to reach full maturity before detaching to become a tomont once
more.
Pathology
 Velvet (in an aquarium environment) is usually spread by contaminated tanks, fish, and
tools (such as nets or testing supplies). There are also rare reports of frozen live foods
(such as bloodworms) containing dormant forms of the species. Frequently, however, the
parasite is endemic to a fish, and only causes a noticeable "outbreak" after the fish's
immune system is compromised for some other reason. The disease is highly contagious
and can prove fatal to fish.
Transmission Mode
 Also known as Rust or Gold Dust disease, Velvet is caused by tiny parasite known as
Oodinium that gives the fish a dusty, slimy look. Velvet is one of the common goldfish
diseases cause by un-quarantined new goldfish
 Its life cycle is very similar to that of Ich. You must treat the whole tank as a single
parasite can produce a new generation.
 This disease is highly contagious and can prove fatal. It's usually spread by contaminated
tanks, fish or tools like testing supplies or nets.

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 Velvet (in an aquarium environment) is usually spread by contaminated tanks, fish, and
tools (such as nets or testing supplies). There are also rare reports of frozen live foods
(such as bloodworms) containing dormant forms of the species.
Sign and Symptoms
1. Scratching body against hard objects
2. Fish is lethargic
3. Loss of appetite and weight loss
4. Rapid, labored breathing
5. Fins clamped against the body
6. Fine yellow or rusty colored film on the skin (giving a velvety appearance)
7. In advanced stages, skin peels off
Diagnosis
 Fish may rub, scratch or flick its body on surfaces in the tank to dislodge the Oodinium
parasite. Velvet disease appears as yellow, rust or gold-dust coloured spots or film on the
body of the fish which gives it a velvet-like appearance. Usually there are not clinical
sing in the fish with one or up to few tens of parasite specimens the early diseases phase
in creosed fiashing fish scratch their skin on the substrate typical later fish may becaome
yellow diseased fish are lethargic
Treatment
• Raise water temperature
• Dim lights for several days
• Add aquarium salt
• Treat with copper sulfate for ten days
• Discontinue carbon filtration during treatment
• Velvet is highly contagious and usually far advanced before being diagnosed, it is
important to take steps to treat it as soon as possible. Treatment is targeted at the free-
swimming stage (tomite) of the parasite.
• Copper sulfate is the treatment of choice. It should be used according to the
manufacturer’s instructions for a full ten days to ensure that the parasite is completely
eradicated. Atabrine (quinacrine hydrochloride) is another medication that can be used to
treat Velvet.

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• Because Oodinium is dependent on light, dimming the aquarium lights aids in
eliminating the infestation. Increasing the water temperature to 82 degrees F will speed
the life cycle of the parasite, making it faster to treat and infestation. Adding salt to the
water (1 to 3 level teaspoons per gallon of water) will increase the mucus production of
the fish to help deter the parasite and will reduce the osmotic stress in the water.
Whenever adding any treatment to the aquarium water, activated carbon should be
removed from the filter, as it will remove the drugs from the water.
Prevention and Control
• Quarantine new fish for two weeks before putting them in your aquarium
• Maintain high water quality
• Provide fish with a nutritionally balanced diet
• Velvet usually only arises when poor aquarium conditions prevail and is highly
infectious. Quarantine of new fish for two weeks will greatly reduce the likelihood of
contaminating a healthy established aquarium. Any fish that appear to be ill should
immediately be removed from the aquarium and kept in a hospital tank to avoid the
spread of the parasite
(2)Aeromonas Hydrophila (Dropsy)
Aeromonas Hydrophila
 Aeromonas hydrophila is a heterotrophic, Gram-negative, rod-shaped bacterium
mainly found in areas with a warm climate. This bacterium can be found in fresh or
brackish water. It can survive in aerobic and anaerobic environments, and can digest
materials such as gelatin and hemoglobin. A. hydrophila was isolated from humans and
animals in the 1950s. It is the most well known of the species of Aeromonas. It is
resistant to most common antibiotics and cold temperatures and is oxidase - and indole -
positive.
Fish and amphibians
 Aeromonas hydrophila is associated with diseases mainly found in freshwater fish and
amphibians, because these organisms live in aquatic environments. It is linked to a
disease found in frogs called red leg, which causes internal, sometimes fatal
hemorrhaging. When infected with A. hydrophila, fish develop ulcers, tail rot, fin rot,

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and hemorrhagic septicemia. Hemorrhagic septicaemia causes lesions that lead to scale
shedding, hemorrhages in the gills and anal area, ulcers, exophthalmia, and abdominal
swelling.
Dropsy (Fish Disease)
 Dropsy is a disease in fish caused by the buildup of fluid inside the body cavity or
tissues. As a symptom rather than a disease, it can indicate a number of underlying
diseases, including bacterial infections, parasitic infections, or liver dysfunction
 Dropsy is an old medical term for a condition that today would be more likely called
edema or ascites—the swelling of soft tissues in a body cavity, such as the abdomen, due
to an accumulation of water and other fluids. The English term derives from the Middle
English word dropesie, from the Old French word hydropse, and from the Greek word
hydrops, which is itself a derivation of hydro, meaning water.
A Disease of Immune-Compromised Fish
 Dropsy in fish is actually a cluster of symptoms caused by an infection from bacteria
commonly present in all aquariums. Consequently, any fish may be exposed to the
dropsy-causing bacteria, but healthy fish rarely fall prey to the disease. Fish are only
susceptible when their immune system has been compromised by some other stress
factor. If all the fish in the tank are under stress, it’s quite common for the entire tank to
become infected, but it is also possible for only one or two fish to fall ill, especially when
prompt action is taken to prevent the spread of the bacteria.
Sign and Symptoms
 As the infection progresses, skin lesions may appear, the belly fills with fluids and
becomes swollen, internal organs are damaged, and ultimately the fish will die. Even with
prompt treatment, the mortality rate is high. Successful treatment is very unlikely unless a
fish is diagnosed in the early stages of the infection
 Symptoms of the underlying bacterial infection can vary widely. Some fish will have the
classic swollen belly, others display skin lesions, while still others show few symptoms at
all. This variability is what makes diagnosis difficult. In most cases, a number of
symptoms are observed, both physical and behavioral.
 Grossly swollen belly
 Scales that stand out with a pinecone-like appearance
 Eyes that bulge
 Gills that are pale
 The anus that becomes red and swollen
 Faces that are pale and stringy
 Ulcers on the body, along the lateral line
 General lethargy

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 Refusal to eat
 Swimming near the surface
Causes of Dropsy
 The agent that causes the symptoms of dropsy is usually the very common Aeromonas
bacteria, one of several gram-negative bacteria present in most aquarium habitats. The
bacteria are known as gram-negative because they do not take on a specific stain used in
the Gram Stain method of identifying bacteria species
 The bacteria will only lead to serious infection in a fish that already has a compromised
immune system. This can happen as the result of stress from a number of factors, such as:
 Poor water quality
 Ammonia or nitrite spikes
 A large drop in water temperature
 Stress from transportation
 Improper nutrition
 Generally, a single or short-term exposure to stress will not compromise the ability of the
fish to fight infection. In most cases, the stress exposure must be present for an extended
period of time, or several stress factors must occur in rapid succession, in order to affect
the fish's immune system.
Treatment
 The infection causing dropsy is not easily cured. Some experts recommend that all
affected fish be euthanized to prevent the spread of the infection to healthy fish. Also,
when combined with popeye , the prognosis is bleak. However, if the infection is
detected early and the fish are isolated for proper treatment, it is possible to save affected
fish. Treatment is geared toward correcting the underlying problem and providing
supportive care to the sick fish:
 Move the sick fish to a "hospital tank."
 Add 1 teaspoon of salt per gallon of water in the hospital tank
Feed the fish fresh, high-quality foods.
 Treat the fish with antibiotics, either in the food or in the water.
 Test the water in the hospital tank daily to ensure it is appropriate for the fish.
 Provide the ill fish with a variety of fresh, high-quality food. Often this is enough to
resolve the infection in cases that are not too far advanced, if the fish is still eating. Keep
the fish under observation for several weeks after the symptoms disappear.
Prevention and Control
 As with many diseases, prevention is the best cure. Almost all the factors that stress fish
enough to make them susceptible to infection can be prevented. Because poor water

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quality is the most common root cause of stress, tank maintenance is critical. Factors to
keep in mind include:
 Test the aquarium water regularly to ensure it is healthy for your fish.
 Perform regular water changes.
 Keep the tank clean
 Clean the filter regularly.
 Use a gravel vacuum to remove wastes from the bottom of the tank.
 Avoid overcrowding the tank.
 Do not over feed fish.
 Use flake foods within one month of opening the packages.
 Vary your fish's diet.
(3)Columnaris disease (Saddle back disease)
Introduction:
It's a chronic to subacute common bacterial disease caused by Flexibacter
columnaris affecting the most species of fresh water fishes but also occurs in brackish
and sea water fishes characterized by development of area of gray discoloration around
the base of the dorsal fin.
Etiology:
The disease caused by Flexibacter columnaris or Flavobacterium
columnare. While the disease caused by Flexibacter maritimus in
marine fishes. These organisms are gram-negative slender and flexible rods motile by
gliding movement. The organism will not grow on most common laboratory media.
Cytophaga agar has been found the best medium for primary isolation.. A common
feature among these organisms is yellow to yellowish -brown or orange -pigmented
growth on solid media. The organisms belong to larger group often called the yellow-
pigmented bacteria. All freshwater fishes are susceptible to infection with the disease and
also infection occurs in brackish and seawater fishes. Young fishes are more susceptible
than adult ones. The incubation period of columnaris disease is variable, this due to stress

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factors, which fishes are subject. The incubation period being less than 24 hours losses
can occur after two to three days.
Mode of transmission:
1) Injuries of the skin or gills help in transmission of the disease.
2) Movement of the infected fishes help in spreading of the infection.
3) Carriers transmitted the infection among fishes.
Clinical signs:
1. On body surface: Small lesions start as areas of pale discoloration at the base of the
pectoral or dorsal fins.. This may have the characteristic appearance of a saddle (saddle
back disease). The surface of these area have slight lemon-yellow colour. Skin becomes
completely eroded. Large numbers of bacteria are present at the advancing edges of the
lesion. The necrosis lead to the complete loss of the pectoral fins and then spreads to the
head region.
2. Gills: have yellow-orange areas of necrosis this start usually at the periphery of the gill
and extend towards the base of the gill arch. Which lead to completely destroy the gill
filament.
3. Loss of appetite and slow swimming.
Diagnosis:
a) Case history.
b) Clinical signs.
c) Microscopical examination: Scrapings from an infected areas of gills and examined
under the microscope with or without staining. Presence of long slender, rod-shaped or
haystack-like colonies or gram-negative organisms assists in diagnosis.
d) Isolation and identification of the causative agent.
e) Slide agglutination, ELTSA and fluorescent antibody test help in diagnosis of the
disease.

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Treatment:
 Potassium permanganate: 500mg/100L for 1 hour by bath method.
 Malachite green: 10mg/100L for 30-96 hours by bath method.
 Oxytetracycline: 50-100mg/kg body weight of fish/day for 10 days.
Prevention:
 Rapid diagnosis and treatment of disease are necessary for practical control of the
disease.
 Stress factors must be avoided.
 Maintenance of nutrition health condition of the fishes will reduce the rate of disease.
 Lowering the temperature (adding cold water) will reduce disease severity.
 Control of F. columnaris infection may be possible by immunization.
(4)Epizootic Ulcerative Syndrome (EUS)
Introduction:
Epizootic ulcerative syndrome (EUS) is considered to be an infection with the
(fungus)oomycete known as Aphanomyces invadans or A. piscicida and characterised
histologically by penetrating hyphae surrounded by granulomatous inflammation. It is an
epizootic condition of wild and farmed freshwater and estuarine fish. EUS has a long
history starting as early as 1975 in Australia and progressed in south east Asian countries
reaching in 1992 in Srilanka and 1994 in Pakistan. This disease can cause damage in a
wide variety of fishes but Chinese carp and tilapia is comparatively resistant.
Channa striatus (striped snakehead), an economically important species is highly affected
by this Infection.
EUS occurs mostly during periods of low temperatures or 18–22°C and after periods of
heavy rainfall

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Etiology:
EUS is a seasonal epizootic condition of great importance in wild and farmed freshwater
and estuarine fish. It has a complex infectious aetiology and is clinically characterised by
the presence of invasive Aphanomyces infection and necrotising ulcerative lesions,
typically leading to a granulomatous response. EUS is also known as red spot disease
(RSD), mycotic granulomatosis (MG) and ulcerative mycosis. The genera Aphanomyces is
a member of a group of organisms commonly known as the water moulds. Aphanomyces
invadans grows best at 20–30°C; it does not grow in-vitro at 37°C. Water salinity over 2
parts per thousand (ppt) can stop spread of the agent. The susceptible life stages of the fish
are usually juvenile and young adults.
Mode of transmission:
 EUS is transmitted horizontally. The Aphanomyces zoospores can be horizontally
transmitted from one fish to another through the water supply.
 Uncontrolled water exchange in fish farms in endemic areas will result in EUS
outbreaks in most of the farms that culture susceptible fish species.
 Motile spore attaches to the skin of the fish, the spore will germinate under suitable
conditions and its hyphae will invade the fish skin, muscular tissue and reach the
internal organs. Fish skeleton muscle is the target organ.
Clinical Signs:
It starts as a red spot in the skin then it eventually becomes an ulcer. As it progresses, the
ulcerative area gets eroded. Infected fish swims with a disintegrated caudal peduncle and
eroded head due to it the high general resistance to infections. The smaller freshwater
fishes such as minnows die much before the infection can erode any organs. It also affects
other Channa sp. and Indian major carps. Ulcers can be in any place of the body.

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Diagnosis:
 Clinical signs
 Isolation of A. invadans from internal tissues.
 EUS outbreaks have been associated with mass mortality in farms during periods of low
temperatures and after periods of heavy rainfall.
 The early signs of the disease include loss of appetite and fish become darker. Infected
fish may float near the surface of the water, and become hyperactive with a very jerky
pattern of movement.
 squash preparations of the skeletal muscle from beneath an ulcer to identify the septate
hyphae of the water mould.
 Grocott’s stain is used for fungal staining. It gives black colouration in the fungal hyphae.
Treatment:
 In the initial stage, application of lime and sodium chloride treatment was found to be
effective.
 CIFA produced a mixture of CIFAX, for controlling EUS but not much standardized.
 Treating the water with chlorine before letting in to the pond, avoidance of water use
from large water body with improper water quality, use of filters in water channels to
avoid wild fish entry and preventing the entry of predatory birds are central to disease
management strategy.
Prevention:
 Infected fish should be moved into high quality water, where they may recover if their
clinical signs are mild.
 If disease occurs eradication is required. Once the disease is eradicated good husbandry,
surveillance and biosecurity measures are necessary to prevent recurrence.

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 In countries free of epizootic ulcerative syndrome, quarantine and health certificates are
necessary for the movement of all live fish to prevent the introduction of the disease.
(5)ENTERIC RED MOUTH DISEASE
INTRODUCTION
Enteric redmouth disease, or simply redmouth disease is a bacterial infection of freshwater
and marine fish caused by the pathogen Yersinia ruckeri. It is primarily found in rainbow
trout (Oncorhynchus mykiss) and other cultured salmonids. The disease is characterized by
subcutaneous hemorrhaging of the mouth, fins, and eyes. It is most commonly seen in fish
farms with poor water quality. Redmouth disease was first discovered in Idaho rainbow trout in
the 1950s.[1] The disease does not infect humans.
ETIOLOGY
Enteric redmouth disease (ERM) is a serious septicemic bacterial disease of salmonid fish
species. It is caused by Yersinia ruckeri, a Gram-negative rod-shaped enterobacterium. It has a
wide host range, broad geographical distribution, and causes significant economic losses in the
fish aquaculture industry.
TRANSMISION MODE
Some fish species serve as vectors for the disease and have subsequently spread the pathogen to
other parts of the world.[1] An example is the fathead minnow (Pimephales promelas) which is
responsible for the spread of redmouth disease to trout in Europe.[2] Other vectors include
the goldfish (Carassius auratus), Atlantic and Pacific salmon (Salmo salar), the emerald
shiner (Notropis atherinoides), and farmed whitefish (Coregonus spp.). Infections have also
occurred in farmed turbot (Scophthalmus maximus), seabass (Dicentrarchus labrax),
and seabream (Sparus auratus).[1] It can now be found in North and South America, Africa, Asia,
and Australia, as well as Europe.
CLINICAL SIGN AND SYMPTOMS

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Infection can cause subcutaneous haemorrhage that presents as reddening of the throat, mouth,
gill tips, and fins, and eventual erosion of the jaw and palate. Hemorrhaging also occurs on
internal organs, and in the later stages of the disease, the abdomen becomes filled with a yellow
fluid - giving the fish a "pot-bellied" appearance. The fish often demonstrate abnormal behavior
and anorexia. Mortality rates can be high.
A presumptive diagnosis can be made based in the history and clinical signs, but definitive
diagnosis requires bacterial culture and serological testing such as ELISA and latex
agglutination.
TREATMENT AND CONTROL
Several antibiotics are available forthe treatmentof redmouth diseaseinfish. Vaccinescanalsobe used
inthe treatmentandpreventionof disease.Managementfactorssuchas maintainingwaterqualityand
a lowstockingdensityare essential fordiseaseprevention.
(6)VIBRIOSIS IN FISHES
INTRODUCTION
Vibriosisisone of the mostprevalentfishdiseases and iscausedby bacteriabelongingtothe
genusVibrio.One of the mostimportantstrainis Vibrioanguillarum whichisof majorimportance
to salmonidfishculture industryandis alsoknownas Red pest of eels.Itisa gram negative curvedand
rod shapedbacteriumwithasingle polarflagellum.Otherspecies(e.g. V.salmonicida) mayhave
numerouspolarflagella. V.anguillarum hasbeendivided intotwoseparate biotypesof which V.
anguillarumbiotypeII has beenrenamedandclassifiedasanew species Vibrio ordalii.It
causeshaemorrhagic septicaemiaand leucopenia.
ETIOLOGY
Vibrio anguillarum isfoundin cultured and wildmarine fish in shallow saltorbrackishwaterduringlate
summer.The pathogenwasthoughtto be spreadby contact withscavengingwildfishfeedingaround
the farms butV. anguillarum,hasbeen foundinthe food of culturedand wildhealthyfish
TRANSMISSION MODE

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Outbreaks of vibriosis have been seen in Pacific and Atlantic salmon, Trout, Turbot, Striped
bass, Winter flounder, Cod, Red sea-bream, European and Japanese eel, Saithe (Pollachius
Virens), Gilthead sea-bream, Sea mullet, Seriola, Channel catfish, Milkfish, Ayu, and Tilapia. It
can also affect molluscs and crustacean including European and Japanese oyster, clam, lobster
and shrimp.
Disease outbreaks can be influenced by water quality and temperature, the strain and
virulence of the Vibrio bacteria and the amount of stress imposed upon the fish.
CLINICAL SIGN AND SYMPTOMS
Clinical signs of vibriosis are haemorrhage to intestines, body cavity, spleen and
muscle, distended mucoid and necrotic intestine and petechiation, erosion and darkended
colouration to the skin and fins. Changes to the eyes include distension and cloudiness and
periorbital swelling. White/grey lesions can be found on the intestines and spleen and in fry,
splenomegaly can be seen.
V. damsela and V.vulnificus cause severe, progressive necrotizing infection in humans.
DIAGNOSIS
Presumptivediagnosiscanbe made fromclinical signsespeciallycharacteristicredspots,swollenand
dark lesionsonthe skinthatbleedandophthalmicchanges;althoughsome acute andsevere casesdie
withoutclinical signs.With V.anguillarum more severe pathologyisseenin the descending
gastrointestinal tract as the conditionsbecome more alkaline.Mosttissuesare septicwithnoevidence
of phagocytosis.
TREATMENT AND CONTROL
Fishcan be treatedwith ampicillin,chloramphenicol,nalidixicacidderivatives,nitrofurans,
sulphonamidesandtrimethoprim.Drug resistantstrainshave appearedbecauseof extensive use of
these chemicals.
A formalin-killed V. anguillarium vaccine is available and can be administered via
intraperitoneal injection, immersion or oral administration.
(7)Brown spot disease (Shell disease or Rust disease)
Introduction – The presence of brown or black spots on shrimp is a syndrome related to

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bacterial or fungal cuticle, appendages or gills, causing commercial depreciation of the product.
It’s scientific name is chitinolytic bacteria (gram negative rods).
Etiology – Bacteria such as Vibrio spp., Aeromonas spp., and Flavobacterium spp., with
chitinolytic activity.
Transmission mode – The operations of capture, transport and handling in general, must be
carried out with extreme caution in order not to cause micro cracks to the carapace, which can
become infected for the presence of Vibrio species opportunist. The precautions are especially
important in the case of individuals for breeding, since the early transmission of the disease (eggs
and larvae) causes high mortality.
Signs and Symptoms - The affected animals show presence of brownish to black eroded areas
on the body surface and appendages.
Diagnosis - Diagnosis of brown spot disease is achieved by simple observations on the gross
signs and symptoms and confirmed by isolation of the bacteria from the site of infection on
Zobell’s Marine Agar and identification of the pathogen.
Treatment – No known treatment. Shell disease can be managed in captive and cultured
populations by reducing crowding, wound avoidance, proper husbandry and system hygiene.
Prevention -Reduce organic load in water by increased water exchange. Avoid unnecessary
handling and overcrowding to minimize chances of injury and infection.
Control - Induction of moulting by applying tea seed cake may be useful. Improve water
quality by increasing water exchange. Although antibiotics may be useful their use in the
culture system is not recommended.
(8)FUNGAL DISEASE (larval mycosis in shrimp)
Introduction - It is one of the most devastating diseases in shrimp hatcheries. However, larval
mycosis has been successfully controlled during the recent years with better management
practices.

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Etiology- Oomycetous fungi, Lagenidium spp, Sirolpidium spp, and Haliphthoros spp. These
fungi are filamentous, non-septate and coenocytic. Upon infection, the fungal mycelium replaces
the larval tissues and ramifies into various parts of the body. Vegetative propagation of these
fungi is through production of bi-flagellate zoospores, which are released into the rearing
medium. These zoospores further infect fresh shrimp larvae. These fungi can be isolated on
peptone yeast extract glucose (PYG) agar or Saboraud's dextrose agar.
Transmission mode – Direct contact. Vegetative propagation of these fungi is through
production of biflagellate zoospores, which are released into the environment these zoospores
further infect fresh shrimp larvae.
Sign and symptoms - Affected shrimp larvae appear opaque and weak. The protozoeal and
mysis stages are highly susceptible. Within 1-2 days, whole stock of shrimp larvae may suffer
mortality.
Diagnosis - Microscopic demonstration of presence of extensively branched non-septate,
fungal hyphae within the body cavity of the shrimp larvae. The fungus can be identified by
microscopic examination of its characteristic canoe shaped micro-conidia. Other oomycetous
fungi such as Saprolegnia spp. and Leptolegnia spp. are also known to affect shell of shrimp
and produce dark necrotic lesions causing gradual mortality.
Treatment – Treflan or trifluralin at 0.2 ppm for 24 hrs.
Prevention - Remove bottom sediments and dead larvae periodically. Disinfect the tanks and
other equipment in the hatchery from time to time. Reduce stocking density. Increase water
circulation.
Control – Observe rigid water management and sanitation. Disinfect eggs with detergent at
20ppm fir 2 hrs long before hatching. Treat spawners with 5 ppm treflan bath for
1 h.

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(9)FINROT
INTRODUCTION-
Fin rot is a symptom of disease or the actual disease in fish. This is a disease which is most
often observed in aquaria and aquaculture, but can also occur in natural populations. Finrot
disease mainly IMC, exotic carp and cat fishes.
Betta fish
ECTIOLOGY-
Fin rot can be the result of a bacterial infection (Pseudomonas fluorescens, which causes a
ragged rotting of the fin), or as a fungal infection (which rots the fin more evenly and is more
likely to produce a white "edge"). Sometimes, both types of infection are seen together.
TRANSMISTION MODE-
Infection is commonly brought on by bad water conditions, injury, poor diet, stress, or as a
secondary infection in a fish which is already stressed by other disease.
SIGN-
Fin rot starts at the edge of the fins, and destroys more and more tissue until it reaches the fin
base. If it does reach the fin base, the fish will never be able to regenerate the lost tissue.
Symptoms-
 Fin edges turn black / brown
 Fins fray
 Base of fins inflamed

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 Entire fin may rot away or fall off in large chunks
 Fins have white dots
Treatment-
 Change the water and check the filter
 Find out the pH and correct it if necessary.
 Treat with a suitable treatment such as phenoxyethanol, malachite green methylene blue
 Use antibiotics if the rotting is jagged.
 Use antifungal medication if the rot is more evenly spread out and the fin has holes. This
may also be a symptom of an external columnaris infection, especially if it progresses
rapidly (within 24 hours) and the rotted edge has a white, fuzzy appearance.
(10) Bacterial shell fish disease
INTRODUCTION-
BROWN SPOT DISEASE (litopenaeus vannamei )- The presence of brown to black spots on
shrimp Litopenaeus vannamei is a syndrome related to bacterial or fungal cuticle, appendages or
gills, causing commercial depreciation of the product.
Etiology-
the presence of dark Brown spots to black in the exoskeleton and appendages, stooped posture,
muscles infected by Psudomonas and Aeromonas genera with inflammation and necrosis,

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together with a high mortality. The aspects evaluated as a diagnostic to define a septic process,
defined as the inability to conduct the cultivation of the species under the conditions tested.
Transmition mode-
Poor water quality parameter
Unhygienic condition
Poor handling
Unhygienic condition of pond
Sign -
The disease manifests itself as brownish to black, single or multiple, eroded areas on the general
body cuticle ,appendages ,and gills.
In larval and post larval stages ,the affected appendages shows a cigarette butt-like appearance
Symptoms-
(a)-Diseased panaeids are examined for appearance of multfocal melanized cuticular lesions on
the cuticle or general body surface ,the appendages,or the gills.
Prevention and control –
 Maintain good water quality and use nutritionally adequate diets.
 Keep organic load of the at low levels by removing sediments
 Minimize handling and overcrowding and reduce other forms of stress.
 Avoid injuries to the exoskeleton of the shrimps

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(11)RED SEA BREAM IRIDOVIRAL DISEASE
(RSIVD)
RSIVD is a major cause of death of farmed red sea bream and more than 30 other farmed
marine fish species. The disease was first recorded in Japan. It can also be found in many East
and South-East Asian countries. Outbreaks are mostly seen in the summer season at water
temperatures of 25°C and above.
Aetiological agent
RSIVD is caused by infection with red sea bream iridovirus (RSIV), from the genus
Megalocytivirus within the family Iridoviridae, including many viruses that are considered to be
synonyms of RSIV. The disease is also caused by infectious spleen and kidney necrosis virus
(ISKNV), which is one of the viruses related to, but distinct from, RSIV. A number of other
iridoviruses that cause similar diseases in ornamental freshwater fish have been reported. These
viruses are difficult to distinguish genetically from ISKNV, and it has not been determined
whether these diseases should be included in RSIVD.
Signs
Animals with this disease may show one or more of these signs, but the pathogen may
still be present in the absence of any signs. Disease signs at the farm, tank or pond level are:
 low to high mortality
 lethargic swimming obvious opercular movement (increased respiratory effort).
Gross pathological signs are
 dark skin (change in skin colour is a significant gross sign)
 petechial (pinpoint) haemorrhage of the gills
 pale gills and enlarged spleen.
Microscopic pathological signs are:
 enlarged cells, deeply giemsa positive, in the spleen, heart, kidney, liver and gills of
infected fish, which are characteristic of this disease small dark spots within fresh wet
mounts of gill lamellae (melano-macrophage centres).
Epidemiology

21
 RSIVD is highly contagious.
 Juveniles are more susceptible to disease than adults.
 Mortality is highly variable (0% to 100%) and can depend on water temperature, with
higher mortalities occurring at higher water temperatures.
 Transmission is horizontal, via the water column from other infected fish. Vertical
transmission has yet to be confirmed.
 Outbreaks of disease occur at water temperatures greater than 20°C, with viral
multiplication increasing with water temperatures up to at least 28°C.
 The virus is stable within tissue to –80°C, and can be inactivated by ether, chloroform
and formalin.
Differential diagnosis
The list of similar diseases in the next section refers only to the diseases covered by this
field guide. Gross pathological signs may also be representative of diseases not included in this
guide. Do not rely on gross signs to provide a definitive diagnosis. Use them as a tool to help
identify the listed diseases that most closely account for the observed signs.
Similar diseases
Epizootic haematopoietic necrosis (EHN), grouper iridoviral disease, infection with
infectious spleen and kidney necrosis virus (ISKNV)-like viruses and Tilapia lake virus (TiLV)
disease.
Control and prevention
Vaccination Effective formalin-killed commercial vaccines for RSIVD are currently
available for red sea bream, striped jack and other fish species belonging to the genus Seriola in
Japan. Protection of fish belonging to the genus Oplegnathus by vaccination is difficult.
Chemotherapy- Not available.
Immunostimulation- Under investigation.
Resistance breeding -Under investigation.
Restocking with resistant species -Under investigation.
Blocking agents -Unknown.
Disinfection of eggs and larvae -No data available.
General husbandry practices
A number of general husbandry practices are used to reduce RSIVD-associated losses.
These include: introducing pathogen-free fish; implementing hygiene practices on farms; and

22
avoiding practices that can decrease water quality and/or increase stress, such as overcrowding
and overfeeding.
Sample collection
Only trained personnel should collect samples. Using only gross pathological signs to
differentiate between diseases is not reliable, and some aquatic animal disease agents pose a risk
to humans. If you are not appropriately trained, phone your state or territory hotline number and
report your observations. If you have to collect samples, the agency taking your call will advise
you on the appropriate course of action. Local or district fisheries or veterinary authorities may
also advise on sampling.
.

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