A disease in an abnormal condition of body function or structure that is considered to be harmful to the affected individual. In this broad sense, it sometimes includes injuries, disorders, syndromes, infections, isolated symptoms deviant behaviors and typical variation of structure and function. This disease is caused by various factors. Some times it caused by some pathogens such as virus, bacteria, fungus and parasites. Some times it caused by non pathogenic factors such as environmental factor, hereditary defects, glandular dysfunction, dietary deficiency or some abnormal cell growth. The disease which is caused by pathogen is called infectious diseases. From different pathogen bacteria most harmful and cause some harmful disease in fish.
Bacteria are unicellular organisms have a massive reproductive potential which make it harmful diseases causing agent. Bacterial diseases have a significant impact on cyprinids and can equally affect both wild and cultured cyprinids. Stress and crowding will favors the transmission of bacterial disease. Some cyprinid establish favourable transmission conditions for pathogens by forming into vast shoals, especially at spawning times. Some diseases are the result of the obligate bacterial pathogen. Bacteria also cause or act as an agent of secondary infection.
Some important bacterial diseases are observed in some fishes, which is discussed bellow with symptoms and remedial action.
Furunculosis:
Furunculosis disease is a well known bacterial disease in fishes. Furunculosis of salmonids is the designation presently recognized (Gittino, 1968) for an epidemic bacteriosis of freshwater salmonids and occasionally brackish water fishes. The first mention of this disease was made in Germany by Emmerich and Weibel (1890, 1894) as a basilus disease in trout culture in a Bavarian fish farm. Since Emmerich and Weibel noted that boils (Furunkle) appeared in the disease region of the torso, the disease has been turned as furunculosis. The causing agent or pathogen, host, symptom and remedial measure of furunculosis disease are mentioned bellow.
Pathogen:
Aeromonas salmonicida.
Host:
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Freshwater salmonids, occasionally brackish water fish
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Cyprinids and non cyprinids fish
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It also infects species of warm and cold water fishes.
Symptoms:
There are four symptomatilogically and epizootiologically different forms are observed in furunculosis disease.
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Ulcerative form
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Hemorrhagic form
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Intestinal furunculosis
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Asymptomatic form.
Before describing these type of form some condition of the furunculosis disease should be mentioned which is described by Herman(1968). He divided theses into four types.
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Acute type: death is rapid without manifestation of external signs in this condition.
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Sub acute type: In this condition death occurs with the formation of furuncles. It is less harmful than acute type.
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Chronic type: here death occurs after the appearance to a certain degree of sign such as enteritis and hemorrhaging at the fin.
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Latent type: in this condition pathological bacteria are isolated but signs do not appear and death does not occur.
Now the symptoms are discussed by different form.
Ulcerative form: the ulcerative is characterized by open ulcer on the back and side of the body. These arises from the deep lying hemorrhagic muscle necrosis which can become visible, initially as clear slightly raised, occasionally dark colored boils. The ulcers have a diameter of 2-20mm and are highly necrotic with white marginal zones. The ulcerative form is seen in chronically or sub acutely infected fish. The losses among salmon caused by the ulcerative form are quite significant.
Hemorrhagic form: Hemorrhagic form exists as acute to highly acute (rarely sub acute), since it rapidly causes considerable mortality. Puntiform bleeding and petechiae appear in the viscera, especially the liver and also on the skin, gills, musculature and the base of the fin. In the kidneys, besides bleeding, degenerative changes and necrosis of the hematopoietic connective tissue are fond. The hemorrhagic form occurs most frequently in the large salmonids in the hatcheries.
Intestinal furunculosis: Intestinal furunculosis is more or less confined to the intestine. The intestine become very large and its blood vessels are enlarged. Hemorrhage occurs especially in the pyloric caeca. Blood cells can often identify in the intestinal content and the inflamed anus protrudes.
Asymptomatic form: the asymptomatic form is often considered the most dangerous one. It causes heavy losses and difficult to diagnose.
Remedial measure: the following should be considered among the measure of general prophylaxis in a hatchery.
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Maintain an optimum prevailing environment (02, NH3, pH, temperature, Fe).
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Feeding fish a balanced diet.
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Cleanliness and orderliness in the in the hatcheries as a consistent sanitary measure.
To prevent the invasion of bacteria in the fish farms which are not contaminated with the bacteria,
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Eggs should be disinfected during transfer of eggs in the eyed stage.
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Organic ionic agents would be the best disinfectant.
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Organic ionic agents diluted to an effective iodine concentration of 100 ppm, eggs are immersed for 10-15 minutes (10-150c).
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pH of the water is set at 7(6-8).
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0.5 g of sodium bicarbonate may be added to 1 letter of soft water.
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Overcrowding should naturally be avoided and the avoidance of stress which are the source of infection.
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Cultivation of disease resistance strains of fish would be another preventive measure but that has not been carried out yet.
Vaccine:
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Prevention by vaccine would be most desirable.
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Vaccines in some cases import resistance to fish and are effective to a certain degree.
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Fish normally infected and subjected to oral administration of vaccine usually have lower mortality rates than other treatment. [Source: Egusa shuzo; 1992. Infectious disease of fish, page:179]
Other Aeromonas and Pseudomonas infections:
Red fin disease of eel:
Eel in the cultivation ponds, are characterized by reddening developing due to hyperemia and hemorrhaging on the anal fins and on the skins of the ventral surface of the head and body.
Pathogen:
Aeromonas hydrophila.
Host: Eel
Symptoms:
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The skin on the ventral surfaces of the head, trunk, tail, the anal fin and the pectoral fins frequently redden due to hyperemia.
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Hemorrhagic spots and bloches appear with the advance of the disease, ultimately, the entire surface is extremely red.
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Reddening also appears on the dorsal fin and on the dorsal surface of the trunk and tail.
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Diseased fish naturally have poor appetite and they often are stationary near the pond walls.
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During this period they raise there heads swim vertically without much strength.
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Swelling often develops in the head. The skin of the swellings collapses and ulcer often develop(schaperclaus,1930)
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Swellings form on the surface of the head and trunk and that ulceration occurs.
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Small reddening regions develop on the skin in arbitrary places of the head, trunk and tail.
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Intestine hyperemia occasionally seen in the gills.
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Anemia develops in the fish in which the signs have advanced and faded color is also seen.
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Spotty hemorrhaging frequently occurs on the abdominal wall but there is no accumulation of ascities.
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The liver generally exhibits dark reddening due to intance hypermia and hemorrhaging spots are occationally evident.
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The spleen swells, often exhibitin dark reddening, hypermia is exterme in the vains and capilaries and the pulp is engorged with blood generally.
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Extreme degeneration usually occurs in the kidney and hypermia as well as hemorrhaging of the capillaries of the glomeruli.
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The intestine exhibit partial or general reddening externally.
Remedial measures: following measures should be taken to prevent red fin disease.
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This disease could be eliminated through cautious disinfection of cultivation pond and removal of diseased or dead fish from the ponds as soon as they appear. Every effort should be made to ensure a hygienic environment.
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The distribution of bacterial strains with high virulence was clarified and quarantines t prevent fish from infected regions from being transferred to non infected regions would be essential.
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Some oral vaccine treatment should be done to prevent the red fin disease of eel.
Infectious abdominal dropsy:
This disease is also known as Ascites infectious cyprinorum (AIC), infectious ascites, hemorrhagic septicemia of carp, rubella, infectious dropsy of carp ascites infectious cyprinorium, hydropisie infectious.
Pathogen:
Aeromonas hydrophila
Host: mostly common carp, some times other carp.
Symptoms:
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The most conspicuous signs of the infectious abdominal dropsy syndrome are first abdominal dropsy, ascites(chiefly in the acute spring stage), and second abscesses and ulcers which occur additionally or only in the skin as “erythrodarmatitis”.
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Fairly marked swelling of the abdomen due to accumulation of fluid in the body cavityand the frequent occurrence of ulcers in the stratum spongiosum or close bellow the skin.
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The ulcerative form was rare in the beginning. After long period of infection, when the epizootic changed to a chronic state, numerous ulcers were observed.
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It was not that only ascites that appeared at one time and only ulcers appeared another time. Both ascites and ulcers, along with other symptoms belong to the infectious abnormal dropsy syndrome produced by hydrophila – punctata group.
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Actually infected fish come up gasping to the surface.
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The eye rotation reflex is reduced or absent.
Skin:
When the infection is mild, the skin can become somewhat pale red or covered with a whitish film
This white film is termed as “death-coat”
Skin edema has been observed in the advanced disease, leading to scaly roughness (lepidorthosis)
A partial atrophy of the epidermis and the stratum spongiosum of the skin is often striking among carp.
Blisters can also form un the spongy layer; these are filled with serous fluid and often appear as small thickenings and indurations, especially on the lateral line
Flat hemorrhagic inflammations are petechial bleedings in the mouth can also become noticeable.
With the formation of concentrated, local centers of inflammation, there appear skin abscesses or ulcers which project outward. I n the center of such an ulcer the denuded red musculature is then visible.
Open hemorrhagic inflammations are often noticed on the fish.
Internal organ:
Signs found in varying intensities and close association with ascites are predominant edema (dropsical swelling) in the skin and various internal organs, hydrops universal (general dropsy) lepidorthosis (scaly roughness), exophthalmos (development of staring eyes) and abdominal dropsy
Sometimes the intestinal inflammation is only symptom during healing process.
Since the body cavity is filled with exudates and due to the distension of intestine, the anus which is also inflamed and reddened.
Remedial measures:
All measures which can now be employed to control infectious abnormal dropsy (IAD) can be combined into three categories;
Developing hardness n fish against IAD
- Resistance fortification.
- Natural and artificial immunization, maintaining the immunohomogeneity.
- Improving the condition of carp
Exposure prophylaxis, measures of sanitary hygiene
- Care of diseases-free stocks.
- Isolating infected fish stocks
- Disinfection and hygiene.
Medicinal prophylaxis and therapy.
- Intraperitoneal infection of effective drugs
- Feeding medicated feed.
- Inter nal application of drugs with catheter.
- Medicinal baths.
Resistance fortification:
By artificially infecting the spawning carp and selecting the resistance fish among them the mortality rate can be reduced.
Natural and artificial immunization, maintaining the immunohomogeneity:
Artificial active immunization can be used successfully. Active often offers several advantages as againbest the prophylactic administration medicaments.
Medicinal prophylaxis and therapy:
Carp which are suffering from ascites and ulcers could be cured or relieved from teor latent infection by a single intraperitoneal infection of Chloramphenial or Streptomycin.
Vibriosis:
The bacterial infection of fresh water fish and salt water fish due to members of the genus Vibrio is termed vibrio diseases or vibrisis. Vibriosis is an enzootic diseases of fish, recoded from all over world. According to Anderson & Conroy (1970), it has already occurred in Eels in salt water ponds along Italian coast in early 19th century. It has known as the Red pest (Peste Rossa) inducing reddening of the body and fins with internal hemorrhaging leading to death.
Pathogen:
Vibrio anguilarum
Vibrio parahaemolyticus.
Vibrio hervei
Host: Freshwater, brackish water and saltwater fishes, carp, Eel. Trout, Gold fish, Angel fish, Cod, Founder, Pike, Kelli fish, Herring.
Symptoms:
Two forms can be observed in the course of vibriosis; acute and chronic.
Acute form: associated with the general infection of entire organism.
Chronic form: associated with local infections especially of the skin, musculature and intestine. Infecton with Vibrio parahaemolyticus can either lead toacute septicemic diseases signs or have a latent couse. The following signs can be observed not only in fish diseases in natural bodies of water, cultured waters and aquaria but also in those artificially infected.
Acute course:
Highly virulent vibriosis can result in death without visible signs.
In general, there is a development of hemorrhages and erythema on fins or other parts of the body which can advance to a reddening over entire body.
Swelling of he spleen and kidney, hyperemia in the internal organs and hemorrhages in the entire body cavity.
A pronounced anemia occurs as a result of the decreases in the number of erythrocytes.
Chronic courses:
In the case of less susceptible fish species or those with a favorable state of immunity, there are mostly only local infections which can be characterized by intramuscular phlegmons with body contents, ulcers or shallow lesions on different parts of the body.
At times, only on intestinal inflammations occurs.
In the case of chronic infection the pathogen can generally be isolated only from the affected parts.
Remedial measures:
It is not possible to control vibriosis among in natural bodies of water. Here prophylaxis can only be directed toward removing the infected fish from the body of water.
Vibrio anguilarum has a high sensitivity to chlorophenicol, oxytetrocycline, nitrofurantoin, chlortetracycline, novobiocin, pterider 0/129, nifurpirinol, sulfamerazine, soluthiazomide, tetramycine with sulfadiazine, sulfanilamide, sulfathiazole, sulfamethoxy pyridazine and sulfamethylphenzol.
In the view of high sensitivity of Vibrio anguilarum to several antimicrobiotics,vibriosis inintensive fish production systems can generally be prevented.
Administering furazolidone in the feed therapeutically meaningful only in achronic course of vibriosis with symptoms of intestinal inflammation.
Vibriosis can also be prevented by controlling temperature, fish density nutrition and other parameters.
[Source: Schaper Claus, Wilhelm; 1991, Fish Diseases.Vol-1, page: 509-523]
Myxobacteriosis:
Myxobacteriosis have so far been the most frequently diagnosed diseases of fresh water fish. Outbreaks of these diseases have also occurred in brackish water and seawaters. Aliments due to myxobacters have occurred not only under conditions of intensive fish culture but also under natural conditions and have also caused losses among aquarium fish.
Myxobacteriosis can be subdivided into:
- Columnaris diseases.
- Bacterial cold water diseases.
- Bacterial ill diseases.
Columnaris diseases:
Freshwater and occasionally brackish water fishes are affected by this diseases. It occurs due to branchial and dermal infection of bacteria, Chandrococcus columnaris classified in the order Myxobacterales but since the publication of Bergey’s Mannual of determinative Bacteriology, 8t edition(1974) the name has been amended to Flexibacter columnaris.
Pathogen:
Flexibacter columnaris
Host: Mainly freshwater fishes are affected but saltwater and brackish water fish also found in worm and cold water.
Symptoms:
The first signs of columnaris diseases are small, grey-white, puntiform lesions on the entire surface of the body which may be concentrated particularly on the head, fin, gills and in the mouth cavity.
Gills are most readily attacked. Yellow-white adhesions in various sites on the lamellae and mucous secretions from the ills become extreme.
The gill become dark red due to hyperemia and large numbers of small haemorrhagic spots often appear.
When the number of yellow adhesions in various parts of lamellae increases and grows in size, the soft tissue of the gill filaments and lamellae to which they adhere collapse, leaving cartilage.
The cartilage collapses & develops gaps of various size in various sites of the gills.
Moreover, the gill filaments and lamellae, which have become necrotized and whitened.
Infections in Eels can occur on the skin if the tail and fins near the tails.
The epidermis of infected skin readily collapses and the dermis becomes narcotized and changes color.
Infection in the skin of the mouth occurs in small carp or trout fingerlings.
The skin become inflamed collapses and reddening as well as due to hyperemia n the diseased sections and in the periphery result in the mouth rot.
Some time fins collapses and partial losses of fins develops.
Virtually all bacteria in the branchial diseased sections form colonies othe surface of branchial lamellar tissue.
Here the collapse of branchial tissue readily occurs.
Hyperemia, swelling and occasional internal hemorrhaging are also evident.
[Source: Ehusa, Shuzo;1992, infectious Diseases of fish, page250-253.]
Two form of the course of columnaris diseases can be distinguished.
Chronic course: Caused by a weekly virulent pathogen, death occurs only after extensive damage to the skin.
Acute course: Caused by a highly virulent pathogen; the diseases generally occurs without symptoms and progress rapidly. There is a general (systemic) infection.
Remedial measures:
Prevention by avoiding of overcrowding and not handling or nettng durng times of elevated water temperature is of utmost interest.
All activity that may lead to epithelial damage such as, transplantation, weighing, sorting etc. should be restricted to minimum necessary.
Feeding the best quality diets, ensuring optimum environmental conditions and careful handling of the fish constitute together the best prophylaxis columnaris diseases.
Baths with disinfectants, dyes, chemotherapeutics, and antibiotics have been recommended for the therapeutic treatment of local columnaris infections.
The large scale practice of bathes trypaflavine has proved very effective for treating local columnaris infections among Eel, carp and trout.
General infections are controlled by the oral subcutaneous or intraperitonial administration of antibiotics, sulfonamides and nitofurans.
To treat systemic columnaris diseases, feed with oxytetra cycline in a doses of 50-100 mg /kg of body weight for ten days or orally administering sulfonamides n a dosage of 200-240 mg/kg of body weight over ten days has proved successful in actual practice.
Bacterial cold water diseases:
The myxobacterial infectious diseases occurs at water tempterature below 12o C. At first, this disease described as caudal or peduncle diseases, after this Brog (1960) designed t cold water diseases.
Pathogen:
Cytophaga psychrophila.
Host: Salmon, Rainbow trout.
Symptoms:
This disease starts from the adipose fin or dorsal fin of fish body. The outer edge of the fin become white.
The disease spread and necrotized the base of the fin and next the entire peduncle.
In the peduncle, the musculature is attacked and the caudal fin dissipated so that only a stub of tail is left from which the vertebral column often projected.
The gills, heart, peritoneum and spleen sometime infected.
The gills are not locally infected superficially but the pathogens are detected in the respiratory tissue.
Remedial measures:
General measures, such as reducing the density of fish or rearing young fish at higher temperature n closed space, serve as prophylaxs against bacterial cold water diseases.
The prophylactic measure of adding sulfamethazne to the feed at dosages of 44 mg /kg body weight per day is continued until the temperature is more than 10oC.
Maintenance of the fundamental principles of sanitary hygiene reduced the spread of the diseases.
Bacterial gill disease:
This is a myxobacterial infectious disease of the gills of various freshwater fish species with the participaton of predisposing environmental influence.
Pathogen: Cytophaga psychrophila
Host: various fresh water fish, Rainbow trout.
Symptoms:
Large amont of mucus are secreted in he gills in cases the signs have progressed to a certain degree.
The gills exhibit a dark red color due to hyperemia and hemorrhaging and the individual branchial lamellae swell and often become wraped.
Small red spots due to swelling of blood vessels and hemorrhaging appear.
The initial signs are swelling and proliferation of epithelial cells at the tip of the branchial lamellae through the gills and fuson begins.
With further progress of the disease there are necrotic changes in the gills.
Diseased fish reduce their intake of food & ultimately give it up altogether.
They swim principally on the water surface and appear to reach for inflow.
When they are exhausted they finally drift toward the outflow and die there.
Remedial measures:
Since bacterial gill disease represents a secondary infection, attention should be mainly directed toward eliminating the factors which are the primary causes of the disease.
Stress situations (handling, stocking, temperature variations and so on) must be restricted to the minimum or completely eliminated.
Medicinal prophylaxis is carried out by bathes with disinfectants, dyes, and chemotherapeutics.
Mycobacteriosis: (Fish tuberculosis)
Mycobacteriosis due to the infection of bacteria of the genus Mycobacterium has long been known to occur in various species of freshwater and marine fish
Pathogen: Mycobacterium marinum
M. piscium
M. salmoniphilum
Host:
Wild and farmed cyprinids have zoonotic importance
The disease occurs often in fish aquarium, especially in tropic fish and in wild fish
Gold fish Carassius carassius, carp, rainbow trout, salmon are detected by mycobacteriosis
Symptoms:
It is characterized by the formation of large numbers of small nodules or tubercula nodules in the internal organs, mainly in liver, spleen and kidney grayish-white military nodules can be seen
The modules are frequently visible macroscopically as small spots
In addition to the nodules, small necrotic lesions also develop. The appearance of this lesion is frequent in the liver, kidneys and spleen.
In addition various organs such as the gills, heart pyloric caeca, gonads, peritoneum, brain, eyes, muscles and skin are attacked.
Diseased swim bladders are white and filled with liquid sometimes colorless ascetic fluid found in the body cavity
Infected fish appear emaciated stunted and show loss of appetite
Areas of light grey discoloration are present on the body surface and can gay from local areas of scale loss to open
Remedial measures:
In the case of temperate cyprinids prevention is by not cohabitin the stock with water ornamental fish spices
The prompt removal of corpses and drying fish, where feasible will help reduce transmission
There is no significantly effective treatment available but some success has been achieved with ornamentals using multidrug antibiotic therapy.
