Protozoan, bacterial, and fungal diseases are common in fish. Protozoan diseases include those caused by flagellated protozoans like Ichthyobodo necatur, ciliated protozoans like Ichthyophthirius multifilis which causes white spot disease, and myxozoans like Myxobolus cerebralis which causes whirling disease in salmonids. Common bacterial diseases are furunculosis caused by Aeromonas salmonicida, colamnaris caused by Flexibacter columnaris, dropsy caused by Pseudomonas punctata, tuberculosis caused by Mycobacterium species, and bacterial gill disease caused by Myxobacteria. Major fungal diseases are saprolegn

1. TOPIC– Different types of Fish diseases; Protozoan disease, Bacterial disease and Fungal
disease
SubmittedBy – SmritiBiswas

2. Introduction
 Disease is an any harmful deviation from the normal structural or
functional state of an organism, generally associated with certain
signs and symptoms and differing in nature from physical injury.
 Fish also get sick and is affected by various kinds of diseases and
pests, mainly in the intensive and commercial fish culture,
resulting in huge loss to the farmers.
 Fish diseases are caused by a wide range of infectious organisms,
including viruses, bacteria, fungi, protozoan and metazoan
parasites.
 Diseases can be traced to stress, which weakens their immune
systems.

3. Causes and Common symptoms of disease
Symptoms
• Lethargic swimming
• Loss of appetite
• Respiratory distress
• Jumping from the water
• Colour of gills changed
• Fins become frayed
• Patches on the body
• Staying near the water
surface
• Scraping or scratching
themselves against objects
• Weakness
Causes
•Poor water quality
•Fluctuation in temperature
•Improper nutrition
•Access waste deposition

4. Protozoan Disease
Protozoan disease, caused by protozoans. Protozoans
may remain in the host's body for their entire life
cycle or a particular part of their life cycle.
Protozoan disease in fishes are
divided in to three categories -
1)Flagellated Protozoans
2)Ciliated Protozoans
3)Myxozoans

5. 1) Flagellated Protozoans
Ichthyobodo necatur
Flagellated protozoans, very small in size but flat and ovoid when swimming.
Largely affects young and under nourished carp, trout. Uses a sucking
organelle to penetrate host.
Symptoms
Dull spots on body blue slime, pale gills,
haemorrhaging, fin necrosis.
 Loss of appetite, flashing.
Control:
Salmonids need prophylaxis with formalin (1:4000 for 1 hr).
carp need 1% salt bath 30 minutes repeated 3-4 times.

6. 2) Ciliates Protozoans
Ichthyophthirius multifilis (ICH)
Single-celled protozoan type, adult is round in shape, up to 1 mm in diameter,
known as “trophont”. This species causes white spot disease in fishes.
Symptoms:
White pustules in advanced cases.
Sometimes called white spot disease if found
on gills, not found on body.
Control:
Difficult to treat.
Chemotherapy requires treating water, not the fish.
Formalin treatment around 250 ppm.
Malachite green 1.25 ppm daily for 30 min.

7. 3) Myxozoans
Myxobolus cerebralis
Exclusively endoparasites, multicellular during adult life. Causative agent of
Whirling disease in salmonids.
Symptoms:
Development in cartilage, usually young fish,
carriers asymptomatic.
fish exhibits tail chasing when feeding or alarmed,
whirling caused by destruction of inner ear by spores
(loss of equilibrium).
Can cause “blacktail” by controlling production of
chromatophores in spinal column, also “pugnose”,
skeletal deformities.
Control: Non-treatable, avoidance critical UV of water, filtration to less than
10 μM.

8.  Clinical signs of systemic bacterial disease include lethargy, anorexia,
abnormal swimming patterns/spinning, hemorrhagic lesions on the skin,
abdominal distension, exophthalmia and external ulcerative lesions.
 Most bacterial infections are caused by Gram-negative organisms
including the genera -
Aeromonas, Citrobacter, Edwardsiella,
Flavobacterium, Pseudomonas, and
Vibrio.
 Aeromonas is more commonly a pathogen in freshwater fish,
whereas Vibrio usually affects marine fish.

9. 1. Furunculosis
Causative agent – Aeromonas salmonicida
Furunculosis is highly contagious disease that affects fish of all ages. The
infection causes high mortality in salmonids, though some other species
of fish are affected.
TREATMENT
Drain the pond and treat it with slaked lime.
Disinfection may be done with 0.015 % sol. of merthiolate or 0.185 %
sol. of Acriflavin .
Iodine is used to decontaminate the surface of fertilised eggs to prevent
vertical transmission.
Symptoms
 Furuncles involving skin and/or muscle
progressing to lesions.
 Haemorrhages on the skin, mouth and fin bases.
 Bloody discharge from nares/vent, stomach filled with
mucus, blood.

10. 2. Colamnaris (cotton mouth)
Treatment
 Add antibiotic in water .
 Normally used antibiotics include the chloramphenicol ( 10 ppm
repeated at 2 -5 days interval ) and furance ( o.1 – 0.3 ppm ) in
which the infected fishes with cotton mouth disease are kept for a
long time bath.
Causative Organism: Flexibacter
columnaris/Chondrococcus
columnaris.
•Often mistaken for a fungal infection
because of its mold-like lesions.
•Columnaris is a common bacterial
infection in aquarium fish, particularly
livebearing fish and catfish.
Symptoms
• White spots on mouth, edges
of scales, and fins.
• 'Saddleback' lesion near the
dorsal fin.

11. 3. Dropsy
Symptoms
• Swollen belly and scales stand out.
• Eyes bulge.
• Internal organs are affected, most notably the liver
and kidneys.
• Spine may become curved and finsish hangs near
the surface.
Causative agent- Pseudomonas punctata
• Fish suffering from Dropsy often have a hugely swollen belly.
• It was the most feared disease in carp culture.
Treatment
 Removal and complete destruction of fishes. The infected fishes may be cured by a
two minutes dip in 5 mg / KMnO4 sol.
 Resistant strains bacteria may be killed by applying streptomycin or chloromycetin or
oxytetracyclin along with supplementary food or by injecting the severely infected
fishes.

12. 4.Tuberculosis
Causative agent - Mycobacterium species. Mycobacterium can be
present in wild caught as well as captive-bred fish and stay
lurking in our aquariums without us ever realizing it.
SYMPTOMS
• Fin rot , waxy coat on body,
ulcer on body.
• Nodules in the internal organs.
• Loss appetite and loss body weight.
• Loss of scales and loss of colours.
Treatment
 Dip treatment for one minute in 1 : 2000 copper sulphate solution for 3-
4 days may be useful.
 Alternatively the fishes may be destroyed and the pond sterilized with
KMnO4 or with soaked lime restocking.

13. 5. Bacterial gill disease
Causative agent- Myxobacteria
This reduces the ability of the gills to supply oxygen to the blood and results
in mortality if left unchecked.
Symptoms:
Swelling in gill lamellae.
Change in gill colour.
Treatment
Application of antibiotics like neomycin chloramphenicol etc may be
useful in treatment of bacterial gill disease in fishes .

14.  Fungi are colourless (no chlorophyll) and heterotroph.
 Fungi have eukaryotic cell.
 Fungus are responsible for serious an economically
important diesease in Teleosts.

15. 1. SAPROLEGNIASIS
Causative agent: Saprolegnia parasitic, Saprolegnia diclina and Achlya
hoferi are the major etiological agents.
It is fungal disease of fishes and fish eggs caused by member of family
saprolegiaceae.
Symptoms
•The appearance of cotton-like, white to grey
growth on the skin, gills, fins and eyes or eggs of
fish.
•In severe cases, 80% of body may be covered with
fungal growth. In early infections, skin lesions are
gray or white in color.
Treatment and control
Avoiding damage of skin during transportation of fish.
Right kind of food with sufficient amount must be provided to fish.
Over crowding of fish must be prevented.

16. 2. Branchiomycosis (gill rot)
Causative agent: Branchiomyces sanguinis and Branchiomyces
demigrans.
Symptoms:
• Fish become weak in movement.
• There are respiratory distress in infected fish and
fungus develops on or in gill tissue, or penetrates
the blood vessels causing obstruction and necrosis
of gill tissues.
Treatment and control:
Strict sanitation and disinfection are essential for disease control.
Ponds with branchiomycosis should be dried and treated with calcium oxide
or 2 to 3 kg copper sulphate per hectare.
Diseased fish can be treated with malachite green at 0.1mg/l for extended
periods of time or 0.3mg/l for 12 hours.

17. 3. Aspergillomycosis
Causative agent
Infection caused by Aspergillus spp. has increased in the recent
years in fresh water fish.
Symptoms:
•Abdominal distension.
•Darkening of color.
•Fishes showing external symptoms
like white fungoid patches.
Treatment
Salt bath treatment effective in primary stage, authorized
medicines are not available.

18. 4. Ichthyophonosis
Causative agent:
Ichthyophonus hoferi, obligate parasite, spherical or oval in
shape, yellowish-brown and has granulated cytoplasm.
Symptoms
•Fish with slight or moderate infection.
•Fish with advanced infection have rough or
granulomatus skin, the term sandpaper effect is used
to describe the granulomatus appearance.
•Lesions found in the internal organs.
•Infection of liver or kidney lead to abdominal
distension & exophthalmia.
Treatment and control
There are no therapeutic procedures for treatment of
ichthyophonus disease.