Aquaculture-Fish Diseases-Pathology.pptx

This ppt contains details about various diseases (bacterial, viral, fungal and parasitic) affecting the fishes

1. FISH DISEASES Dr. B.Elia , M.Sc., Ph.D Lecturer in Zoology P.R. Govt College (A) Kakinada-533001 ANDHRA PRADESH

2. VIRAL DISEASES IN FISH

3. VIRAL HEMORRHAGIC SEPTICEMIA  ( VHS )

4. VIRAL HEMORRHAGIC SEPTICEMIA  ( VHS )

5. Viral hemorrhagic septicemia  ( VHS ) is a deadly infectious  fish disease  caused by viral hemorrhagic septicemia virus (VHSV). It afflicts fish of over 50 species of freshwater and marine fish in several parts of the  northern hemisphere . [ VHS is also known as " Egtved disease," and VHSV as " Egtved virus. Symptoms Fish that become infected experience hemorrhaging of their internal organs, skin, and muscle. Some fish show no external symptoms, but others show signs of infection that include bulging eyes, bloated abdomens, bruised-looking reddish tints to the eyes, skin, gills and fins. Some infected fish have open sores that may look like the lesions from other diseases or from  lamprey  attacks. There may also be a nervous form of the disease where fish are constantly flashing and showing abnormal behaviour.

6. Identification:  Viral Hemorrhagic Septicemia (VHS) is caused by a virus that infects fish in both marine and freshwater environments. Infection signs differ depending on the course of the disease. Some infected fish show no symptoms at all. Others may become hyperactive and display nervous symptoms, such as twisting of the body and erratic swimming. In its most severe form, fish become lethargic and dark, with bulging eyes as well as liver and kidney abnormalities. They also have bleeding in their eyes, skin, gills, fin bases, skeletal muscles, and internal organs. This form of the disease almost always kills the infected fish. In less severe infections, the death rate is low. Survivors may show no outward symptoms, but are capable of carrying and spreading the virus for the rest of their lives.

7. IPN

8. Infectious pancreatic necrosis  (IPN) is a severe  viral disease  of  salmonid fish . It is caused by  infectious pancreatic necrosis virus , which is a member of the  Birnaviridae family . This disease mainly affects  young salmonids , such as  trout  or  salmon , of less than six months, although adult fish may carry the virus without showing symptoms. [1] A sharp rise in mortality is often seen (depending on the  virulence  of the disease). Other clinical signs include  abdominal swelling ,  anorexia , abnormal swimming, darkening of the skin, and trailing of the feces from the  vent . On  necropsy , internal damage (viral  necrosis ) to the  pancreas  and thick mucus in the  intestines  often is present.Surviving fish should recover within one to two weeks.

9. BACTERIAL DISEASES IN FISH

10. Dropsy is a common but often fatal fish disease that causes distinctive raised scales pointing away from the body in an affected fish. Although used as the name of the disease, it is more accurate to say that dropsy describes the symptoms of the disease as it is due to the swelling caused by fluid accumulation in the tissues or body cavities of an animal. The actual cause of the swelling and of the disease consists of a variety of factors, including kidney disease, infection, and nutritional and environmental factors. It is the prominent swelling primarily in the abdominal region of the fish that causes the protrusion of the scales away from the body. This protrusion results in the pine cone-like appearance of the fish.

11. VIBRIOSIS IN SNAPPER

12. Definition: Vibriosis is one of the most prevalent fish diseases caused by bacteria belonging the genus  Vibrio  affecting many marine and fresh water fishes. The disease characterized by septicemia , dermal ulceration, ascitis and haematopiotic necrosis.   Causative agent: The most important etiological agent of vibriosis is  V. Anguillarum

13. Causative agent: The most important etiological agent of vibriosis is  V. Anguillarum Clinical signs: 1.      The course of the infection is rapid and most of the infected fish die without showing any clinical signs. 2.      Anorexia, darkening of the skin and sudden death in young fish. 3.      There is abdominal distension, anemia and dermal hemorrhages . 4.      Red spots found on the ventral and lateral areas of infected fishes. 5.      Congestion and swelling of the spleen, liver and kidney. 6.      There is intestinal hyperemia together with clear viscous fluid within the intestinal tract. 7.      There may be boil like lesions found under the skin and in muscles not much different from furuncle. For this, the disease called saltwater furunculosis in salmonids . 8.      These furuncles break to the exterior and necrotic skin lifted away, leaving large open ulcer. 9.      Eye lesions are common including corneal edema , ulceration and exophthalmos . 10.     Fin rots and paleness of gills may be show in chronic infection.  

14. Definition: Furunculosis is an acute, subacute , chronic or latent disease, primarily among salmonid fishes characterized by formation furuncle or boil-like lesions in various tissues of the body.   Causative agent: The disease is caused by gram-negative, short bacilli called  Aeromonas salmonicida , which is classified into two strains. 1.     Typical  A. salmonicida , isolated  from salmonids only. 2.     Atypical  A. salmonicida , isolated from salmonids & non salmonids species

15. Clinical signs: These are different forms showing on diseased fishes: 1.      Per-acute form :         This form is characterized by rapid death of fish especially young fish, whose defenses against a severe bacterial septicemia will be poor Darkening of skin, rapid breathing and slight exophthalmos may be observed on infected fish. Cardiac damage is a possible cause of death. 2.      Acute form : Fish with an acute infection show signs of hemorrhagic septicemia , including body and vents. Skin lesions may be haemorrhagic patches along the side or on the dorsal body surface, hemorrhages at base of fins. Darkening of skin and sluggishness in movement. Hemorrhages scattered over abdominal walls, viscera and heart. Soft and friable or liquefied kidney is observed. Enlarged spleen with round edges. Pale liver with subcapsular haemorrhages. Stomach & intestine may contain bloody mucous. Swim bladder is hyperaemic. Raised furuncles, which usually develop in the dermis due to localization of bacteria rather than the hypodermis. Fish may die within 2-3 days.

16.   3.      Subacute and chronic form : In this form mortality rate is low & more common in older fish. The clinical includes. Slight darkening of skin, inappetance , and lethargy and congested blood vessels at base of fins. Slight exophthalmos & fish may have pale or congested gills. The furuncle may be small and compact or large & soft. They contain dark red pus with numerous bacteria. The mature furuncle bursts leaving deep ulcer or healed furuncle may leave scar tissue. The furuncle may be found in liver, kidney and spleen. 4.      Intestinal form : This form is associated with low mortality. Prolapse of anus and intestinal inflammation may occur.

17. FIN AND TAIL ROT

18. Causes of Fish Fin Rot Fin Rot is caused by different types of gram-negative bacteria, including Aeromonas , Pseudomonas fluorescens , and Vibrio . These organisms eat away at the membranes of the fish’s fin, leaving them ragged and frayed. The damaged and frayed tissue is then vulnerable to secondary fungal infections. The biggest cause of Fin Rot is the condition of the living environment. Bacteria overgrowth and the spread of disease is much more common in environments with poor water quality. Overfeeding fish can contribute to poor water quality, and overcrowding can cause stress and lead to higher risk of disease. Aggressive fish may damage the fins of other fish, which causes stress and a risk of infection.

19. Fish Fin Rot Symptoms Symptoms of Fin Rot include inflamed patches on the fins, faded color or discoloration on the edges of the fins, and fraying of the fin or tail. Other symptoms include lethargy and loss of appetite. If the disease is left untreated, the disease can spread to other areas of the body.

20. Columnaris   (also referred to as cottonmouth) is a symptom of  disease  in  fish  which results from an  infection  caused by the  Gram-negative , aerobic, rod-shaped  bacterium   Flavobacterium columnare . It was previously known as  Bacillus columnaris , Chondrococcus columnaris , Cytophaga columnaris  and  Flexibacter columnaris . Symptoms An infection will usually first manifest in fish by causing frayed and ragged fins. This is followed by the appearance of ulcerations on the skin, and subsequent epidermal loss, identifiable as white or cloudy, fungus-like patches – particularly on the gill filaments. Mucus often also accumulates on the gills, head and dorsal regions. Gills will change colour, either becoming light or dark brown, and may also manifest necrosis. Fish will breathe rapidly and laboriously as a sign of gill damage. Anorexia and lethargy are common, as are mortalities, especially in young fish.

21. Bacterial Gill disease Definition: It's a chronic to acute disease, affect primarily cultured and aquaria fishes. Disease characterized by respiratory and osmoregulatory impairment.   Causative agent:  Gills disease is caused by several agents: 1.      Myxobacteria ( flavobacterium branchiophilum ) in combination with unfavorable environmental conditions. This type termed (bacterial gill disease). 2.      Deficiency of pantothenic acid. This type is called nutritional gill disease. 3.      Chemical pollution or pesticides with secondary mycotic infection (Haemorrhagic gills disease).

22. Clinical signs: 1.      Food intake by fish is reduced. 2.      Sluggish movement of affected fish. 3.      Fish remain near the water surface and often line up against the water inlet. 4.      One of the most constant symptoms is the increased mucous secretion by the gills. 5.      Gills may be swollen and congested, which results in their appearance deep red than normal. 6.      In advanced cases gills lamellae are clubbed and filaments may be fused together because of hyperplasia of gill epithelium and depris protruding from beneath the operculum. 7.      Signs of bacterial gill disease are white to gray spots on the gills. These spots are apparent when fish swims or turns in the water. 8.      Haemorrhagic gills disease is characterized by the presence of sand-grains size aneurysms in the gill capillaries.

23. BACTERIAL GILL DISEASE

24. RED SPOT DISEASE IN FISH

25. RED SPOT DISEASE IN FISH Epizootic ulcerative syndrome (EUS), also known as red spot disease (RSD) and mycotic granulomatoses (MG), is a seasonal epizootic condition of great importance in wild and farmed freshwater and estuarine fish. The fungus involved in EUS is also known variously as Aphanomyces invadans , A. piscicida , A. invaderis and ERA (EUS-related Aphanomyces ) . Rhabdoviruses have also been associated with particular outbreaks, and secondary Gram-negative bacteria invariably infect EUS lesions. SYMPTOMS When EUS spreads into a fish culture pond, high morbidity (>50%) and high mortality (>50%) might be observed in those years that have a long cold season, with water temperatures between 18 and 22C. Some infected fish may recover when the cold period is over.  EUS can be readily detected in diseased fish specimens collected from EUS-infected areas using histological techniques. Fish may exhibit red spots or small ulcers. 

26. FUNGAL DISEASES IN FISH

27. iii. Fungus ( Saprolegnia ): Water Mold disease Symptoms: Tufts of dirty, cotton-like growth on the skin, can cover large areas of the fish, fish eggs turn white. Fungal attacks always follow some other health problems like parasitic attack, injury, or bacterial infection. The symptoms are a grey or whitish growth in and on the skin and/or fins of the fish. Eventually, if left untreated, these growths will become cottony looking. The fungus, if left untreated, will eventually eat away on the fish until it finally dies. Treatment: Use a solution of phenoxethol at 1% in distilled water. Add 10 ml of this solution per litre. Repeat after a few days if needed, but only once more as three treatments could be dangerous inhabitants. If the symptoms are severe the fish can be removed and treated with small amount of providone iodine or mercurochrome. For attacks on fish eggs, most breeders will use a solution of methylene blue adding 3 to 5 mg/1 as a preventive measure after the eggs are laid.

28. PROTOZOAN DISEASES

29. The major parasitic diseases, which face fish production are caused by: 1.      Protozoa: a.     Ciliates: i .     Ichthyophthirius multifiliis . ii.     Chilodonella . iii.     Tetrahymena . iv.     Trichodina . v.     Ambiphyra . vi.     Apiosoma . vii.     Epistylis . viii.     Capriniana . b.     Flagellates i .     Hexamita . ii.     Ichthyobodo . iii.     Piscinoodinium . iv.     Cryptobia . v.     Myxozoa . vi.     Microsporidia . vii.     Coccidia

30. 2.      Monogenean trematodes : a.      Dactylogyrous   sp . b.      Gyrodactylus spp. 3.      Digenean trematodes 4.      Nematodes 5.      Cestodes 6.      Parasitic Crustacea a.      Ergasilus . b.      Lernaea . c.       Argulus 7.      Leeches.

31. ICHTHYOPHTHIRIASIS OR WHITE SPOT It is one of the most prevalent disease affecting  mostly cultured and aquraium fishes caused by   Ichthyophthirius multifiliis , characterized by presence of white spots allover the external body surface (skin ,fins, gills and body surface). Ichthyophthiriasis comes in front of all parasitic diseases, as it is widespread in all types of intensive culture. Also, outbreaks of this disease lead to mass mortality and reduce the growth rate of fish. In Egypt disease was recorded in numerous fish species such as tilapia carp and ornamental gold fish. Etiology of Ichthyophthiriasis : Disease caused by  Ichthyophthirius multifilliis .

32. Clinical signs: The disease is characterized by appearance of white spots on the skin, gills, fins and cornea of the eye. The white spots appeared as white specks on their skin as though they were sprinkled with salt.  The fish react to the infestation of parasites by irritation, flashing and rubbing on the bottom, swimming violently and holding the fins close to the body. More severe attacks result in skin detachments. When the gills become infected, they appeared pale in color and swollen, respiration become difficult and the fish aggregate at the water inlet and die.

33. Microsporidean parasites (now classified with the fungal organisms) produce a spore-filled cyst within almost any tissue of many freshwater and marine species. As the cysts gets larger, infected muscle tissue becomes displaced and turns white in color .  Pleistophora hyphessobryconis , causes a syndrome called "neon tetra disease" in zebra danios , cichlids and cyprinids. Myxosporideans are a common sporozoan parasite of many species of fish. These parasites form a spore-filled tissue cyst that displaces or disrupts the function of the infected tissue. Coccidial ( Eimeria  sp. and  Goussia  sp.) infections of the intestinal tract and kidney, respectively, are a common occurrence in young fish where infection can cause poor growth, emaciation and death. Infections can also be found in adult fish, but the resulting pathology is generally less severe. SPOROZOAN DISEASE IN FISH

34. Myxobolus cerebralis  is a  myxosporean   parasite  of  salmonids  ( salmon ,  trout , and their allies) that causes  whirling disease  in  farmed salmon and trout and also in  wild fish populations . It was first described in  rainbow trout  in Germany a century ago, but its range has spread and it has appeared in most of Europe (including Russia), the United States, South Africa, Canada and other countries. In the 1980s,  M. cerebralis  was found to require a  tubificid   oligochaete  (a kind of  segmented worm ) to complete its life cycle. The parasite infects its hosts with its cells after piercing them with  polar filaments  ejected from  nematocyst -like capsules. WHIRLING DISEASE IN FISH

35. The fish's tail may darken, but aside from lesions on cartilage, internal organs generally appear healthy. Other symptoms include skeletal deformities and "whirling" behavior (tail-chasing) in young fish, which was thought to have been caused by a loss of equilibrium, but is actually caused by damage to the spinal cord and lower brain stem. Experiments have shown that fish can kill  Myxobolus  in their skin (possibly using  antibodies ), but that the fish do not attack the parasites once they have migrated to the central nervous system. This response varies from species to species.

36. HELMINTH DISEASES

37. DACTYLOGYROSIS

38. Definition: Dactylogyrosis is a parasitic disease caused by species of genus dactylogyrus , affecting the fresh water & marine water fishes characterized by respiratory manifestation.   Etiology : The disease caused by the genus Doctylogyrus . The genus belongs to monogenetic trematodes . There are several recognized species from Dactylogyrus , which they parasitized on freshwater and marine fish. These species are  D.vastator , D.extensus ,   D.anchoratus ,   D.lamellatus  etc.). 

39. Clinical signs: 1.     Infected fish become restless and collect in large number at water inlet. 2.     The gills are pale, sometimes mosaic-patterned & covered with mucus. 3.     Fish gasp for air & their respiration is impeded. 4.     Young fish suffer from inappetence and emaciated. The head becomes large as compared to the body. 5.     Dark coloration can appear among the diseased fishes. 6.     At the point of attachment of the parasites there is destruction of the epithelium & disruption of tissues. 7.     The edge of the gill has grayish coloration & appears clotted & the opercula appear to be somewhat opened. Hyperplasia and necrosed of the gills may occur. 8.     Sometimes develop a white to gray-white areas of thickening mucous on the skin, especially behind the fins or anterior to dorsal fin. 9.     Secondary infection with bacteria or fungi may also present.

40. Gyrodactylus are small, leech-like parasites. Over 400 species have been described, from fish and frogs, in fresh and salt water.  They attach to the host by the attachment organ, or opisthaptor at one end of the body and feed using glands at the other end. Attachment can cause large wounds and feeding can damage the epidermis, allowing secondary infection. 

41. CRUSTACEAN DISEASES

42. ARGULOSIS

43. ARGULUS

44. Clinical Signs: 1.                 Infested fish become irritable 2.                 Flashing 3.                 Loss of scales 4.                 Skin fissures 5.                 Hyperplasia at wound margin 6.                 Caudal peduncle, buccal cavity, and fins 7.                 Secondary infection ARGULOSIS

45. ii. Anchor Worm ( Lernaea ): Symptoms: The fish scrapes itself against objects, whitish-green threads hang out of the fish’s skin with an inflamed area at the point of attachment. Ahchor worms are actually crustaceans. The youngs are free swimming and borrow into the skin, go into the muscles and develop for several months before showing. They release eggs and die. The holes left behind are ugly and may become infected. The anchor worm is too deeply imbedded to safely remove. Treatment: A 10 to 30 minute bath in 10 mg per litre of potassium permanganate, or treat the whole tank with 2 mg per litre, but this method is messy and dyes the water.

46. LERNEA ON MURRAY COD

47. Ergasilus : Symptoms: The fish scrapes itself against objects, whitish-green threads hang out of the fish’s gills. This parasite is like the anchor worm, but is smaller and attacks the gills instead of the skin. Treatment: Treatment can best be done with a 10 to 30 minute bath in 10 mg per litre of potassium permanganate.