SECTION-8 Sustainable Water Resource Management, Policies And Protocols

EPIZOOTIC ULCERATIVE SYNDROME IN FISH AT BARAK VALLEY, ASSAM, INDIA
Devashish Kar1 , S.C. Dey2 , Aurobindo Roy3 and Manabendra Mandal2

ABSTRACT
INTRODUCTION
MAJOR SPECIES AFFECTED AND PATTERN OF SPREAD OF EUS
SYMPTOMS AND GROSS PATHOLOGY
PATTERN OF INVESTIGATION OF EUS
AETIOLOGICAL STUDIES:-BACTERIA
VIRUS
ELECTRON MICROSCOPIC STUDIES
FUNGI
HISTOPATHOLOGY, HAEMOTOLOGY, HISTOCHEMISTRY AND ENZYMOLOGY
CONTROL OF EUS
REFERENCES

ABSTRACT: first topic previous topic next topic last topic

The dreadful fish disease, Epizootic Ulcerative Syndrome (EUS), has been causing large-scale mortality among the freshwater fishes since 1988, initially affecting four species of fishes widely. The study revealed the fluctuation in intensity of disease in relation to species effect. Large hemorrhage cutaneous ulcers, epidermal degeneration and necrosis followed by sloughing of scales are the principal symptoms of EUS. Low total alkalinity could be a pre-disposing 'stress' factor. Sick fishes show low haemoglobin and polymorph, but high ESR and lymphocytes. Communicative nature of EUS revealed a variation in time-gap between fish and infection in different species. Inoculation of microbes into the test animals did not reveal any sign of ulceration for two years. Bacterial culture revealed occurrence of haemolytic E. Coli, Aeromonas hydrophila, Pseudomonas aeruginosa, Klebsiella sp., and Staphylococcus epidermitis in the surface lesions as well as in the gut, liver, gills, heart, kidney and gonads of sick fishes, all of which have been found to be sensitive to Chloramphenicol, Septran, Gentamycin, etc. Fungal isolation revealed occurrence of Aphanomyces sp with concomitant occurrence of the same fungal genus in histological sections of EUS affected fishes. Histopathological studies revealed focal areas of fatty degeneration of hepatocytes surrounding the portal triads in the liver. The preliminary histochemical studies with regard to interruptions in glycogen synthesis and blockade of respiratory pathways are being conducted. Similarly, preliminary enzymological studies are being conducted with regard to the amount of alkaline phosphatase, SGOT, SGPT and LDH. Inoculation of 10% homogenate from EUS affected Clarias batrachus into 80% confluent monolayer of BF 2 fish cell line in Leibovitz L-15 medium revealed progressive CPE at a dilution of 10 which was passable in subsequent cultures; indicating the isolation of the virus. Electron microscopic studies with the ultra-thin sections of still-occurring EUS - affected fish tissues, revealed the presence of virus-like particles (inclusion bodies); and further studies in this regard are being conducted.

INTRODUCTION: first topic previous topic next topic last topic

Fish is a dependable source of animal protein in developing countries like India. Large-scale mortality occurs among the fresh water fishes often due to environmental stress followed by pathogenic attacks and parasitic afflictions (Epizootic Ulcerative Syndrome, EUS) causing a tremendous loss to the nation. Such an epizootic, hitherto unknown, assumed epidemic dimension and has been sweeping a big part of the globe starting from Australia and tropical South-America during early seventies and reaching South - East and south Asia down the years; and in these regions, this epizootic is persisting even today, posing a serious threat to the existence of freshwater fish.

Following reports of Mycotic granulomatosis (MG) in Japan (1972), the earliest report of EUS in Papua New Guinea (1974), most of south-east and south-Asian countries like Indonesia (1980), Malaysia (1979-83), Thailand (1981-85), Kampuchea and Lao PDR (1984), Myanmar (1984-85), Sri-Lanka (1987), Bangladesh (1988), and the Barak valley region of Assam, India (1988). Since then, it has been spreading rapidly causing large-scale mortality among freshwater fishes.

MAJOR SPECIES AFFECTED AND PATTERN OF SPREAD OF EUS: first topic previous topic next topic last topic

A systematic study undertaken since 1988 in India, revealed wide scale attack among four species of fishes, viz, Channa punctatus, Macrognathus aral, Mystus vittatus and Puntius conchonius. Other species affected by EUS during the same period included Aorichthys aor, Amblyphayngodon mola, Catla, Cirrhinus mrigala, Heteropneustes fossils, Labeo rohita, Lepidocephalus guntea, Notopterus notopterus and Salmostoma bacaiia.

The study revealed EUS attack among different species of fishes (other than those mentioned above) during the subsequent years (Kar and Dey 1990 a,b). The recent studies (Kar et.al., 1993;1994;1995a,b; 1996;1997;1998a,b,c;1999 a, b,c,2000a, b) indicated that species like Channa striatus, C. Punctatus, Clarias batrachas and Anabas testudineus have been severely affected by EUS in this region since 1995 and the outbreak has been occurring during the period from November to March. This indicates that there is a differential pattern of species susceptibility as EUS has been spreading through different years.

SYMPTOMS AND GROSS PATHOLOGY: first topic previous topic next topic last topic

EUS is characterised by the occurrence of large haemorrhagic or necrotic ulcerative lesions on the base of fins and other parts of the body, which later become larger inflamed areas with acute degeneration of epidermal tissues.

PATTERN OF INVESTIGATION OF EUS: first topic previous topic next topic last topic

Sniesko (1974) stated that an overt infectious disease occurs when a susceptible host is exposed to virulent pathogen under stress. Field estimation of temperature, turbidity, pH, Dissolved oxygen, free carbon dioxide and conductivity in water; temperature, pH, conductivity, organic carbon and NPK in soil; aquatic macrophytic biomass (AM) and total planktonic count did not reveal any noticeable differences in the values of these parameters obtained during the disease outbreak period in the similar water bodies. This could indicate that, there had not been any severe organic pollution of water and soil in these water bodies; and hence organic pollution of water and soil may not be considered as the principal cause of EUS outbreak in this region. However there has always been severe fall in total alkalinity (TA) values in these water bodies prior to EUS outbreak; thereby causing 'stress' condition for fishes in the water and making them susceptible to attack by the pathogens; leading to the outbreak of EUS (Kar and Dey, 1990a).

Estimation of mercury, lead, Arsenic and Cadmium (by atomic adsorption spectrophotometry), did not reveal any appreciable differences in the quantity of these elements in the water and soil samples of the EUS affected and unaffected waterbodies. This had indicated that, absence of trace element contamination, in the outbreak of EUS (Kar and Dey, 1990 b).

AETIOLOGICAL STUDIES:
BACTERIA: 		first topic previous topic next topic last topic

Regular isolation of bacterial flora from the surface lesion of EUS affected fishes as well as, from, their muscles, gut, liver, gills, heart, kidney and gonads revealed the occurrence of haemolytic strains of Eschericha coli, Aeromonas hydrophila, Pseudomonas aeruginosa, Staphylococcus epidermitis and Klebsiella sp. All these bacteria have been found to be sensitive to chloramphenicol, septran, streptomycin, gentamycin and norfloxacin (Kar et.al, 1999 a).

VIRUS: first topic previous topic next topic last topic

Absence of haemorrhagic septicaemia (which is so characteristic of Aermonas infection) in all but most of the ulcerated fish (Roberts 1989); non-occurrence of these pathogens in the early stages of the disease (Lilley et al., 1992); and close association of these bacteria with the fish since time immemorial (Kar and Dey 1990 b) suggest that A. hydrophila is unlikely to have any primary role in the pathogenesis of EUS. And, a primary viral aetiology has always been suspected to be associated with the initiation of EUS (FAO 1986; Kar et.al., 1990 a).

As a confirmation for the presence of viruses in the EUS - affected tissues, BF 2 fish cell lines was used by infecting the growing cells with filtrate from homogenised tissue of ulcerated Clarias batrachus. A progressive CPE was noticed even at dilution of 10 of a 10% tissue homogenate. The infection was less in the subsequent cultures indicating the isolation of virus (Kar et.al., 1993). Electron microscopic study of the TCF showed occasional round particles unlike those previously reported (Frerichs et.al., 1986).

ELECTRON MICROSCOPIC STUDIES: first topic previous topic next topic last topic

Detailed electron microscopic studies done with ultra thin sections of EUS - affected fish tissues revealed the membrane bound and granular abnormal structures; hepatocytes with vacuolations and virus-like inclusion bodies in the nucleus.

FUNGI: first topic previous topic next topic last topic

Kar et.al., (1999b) isolated Aspergillus sp from diseased fishes in Assam. Subsequently, Kar et. al (2000a) also isolated Aphanomyces sp from the EUS affected fish tissues. However, fungi may not be considered as the primary aetiology in view of the fact that, they have always been associated with fishes in water without generally causing any harm.

HISTOPATHOLOGY, HAEMOTOLOGY, HISTOCHEMISTRY AND ENZYMOLOGY: first topic previous topic next topic last topic

Detailed histopathological (HP) studies (Kar and Upadhyay 1998a) revealed focal areas of increased fibrosis and chronic inflammatory cell infiltration in muscles; focal areas of fatty degeneration of the hepatocytes surrounding the portal triads and occasional infiltration by mononuclear cells in the liver. Preliminary haemotological studies revealed higher DLC and ESR but low Hb content in the blood of EUS affected fishes as compared to the corresponding healthy fishes of the same species (Kar et.al., 1994). Preliminary histochemical studies (Kar and Das 1999 b) revealed interruption of glycogen synthesis in the liver and blockade of respiratory pathways in the gills. Preliminary enzymological studies (Kar 1999a) in the EUS - affected fishes revealed high values of alkaline phosphatase, SGOT, SGPT and LDH.

CONTROL OF EUS: first topic previous topic next topic last topic

Effective control and treatment of EUS is a major problem today, because the primary pathogen has not yet been identified. Control of EUS in large natural water bodies may not be possible. However in view of the fact that TA of water acts as a predisposing 'stress' factor, application of lime in low alkaline water bodies, helps to control the spread of EUS. EUS today is a semi-global problem among the fresh water fishes. Unfortunately, in view of its complex infectious etiology, it is yet to be accurately defined.

REFERENCES: first topic previous topic next topic last topic

  • FAO, 1986. Field and Laboratory Investigations into Ulcerative Fish Disease in the Asia-Pacific region, Food and Agricultural Organisation (Bangkok). 214.
  • Frerichs, G.N., Miller, S.D. and Roberts, R.J., 1986. Ulcerative Rhabdovirus in South-East Asia. Nature 322(6076) 216.
  • Kar D, Dey S C and Mandal M., 2000 b An overview of Epizootic Ulcerative Syndrome in the fishes of India. Proc. International Symposium, Lake 2000, Indian Institute of Science, Bangalore.
  • Kar, D and Das, M., 1999b. Preliminary Histochemical studies on fish tissues affected by Epizootic Ulcerative Syndrome in Assam. Proc. National Symposium on Fish Biotechnology, Central Institute of Fisheries Education, Mumbai, 1:31.
  • Kar, D and Dey, S.C., 1990a. A preliminary study of diseased fishes from Cachar district of Assam, Matsya, 15-16:155-161.
  • Kar, D and Dey, S.C., 1990b. Fish Disease Syndrome: A preliminary study from Assam. Bangladesh J. Zoology, 18:115-118.
  • Kar, D and Upadhyay, T., 1998a. Histopathological study of fishes affected by Epizootic Ulcerative Syndrome in Assam. Proc. National Symposium on Veterinary Pathology, Assam Agricultural University, Guwahati, 24.
  • Kar, D., 1998c. Fish Disease Diagnostics and Fish Quarantine Problems in India and South-East Asia with particular emphasis on Epizootic Ulcerative Syndrome (EUS) -Fish Disease Problems. Proc. International Workshop on Fish Disease Diagnosis and Quarantine, Indian Council of Agricultural Research (ICAR), Ministry of Agriculture (Govt. of India), Network of Aquacultural Centres in Asia (NACA), Food and Agricultural Organisation (FAO) of the United Nation, OIE (France) and Central Institute of Freshwater Aquaculture (CIFA), 1.
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  • Kar, D., 2000a. Epizootic Ulcerative Syndrome Fish disease in Barak valley region of Assam. India. Proc. National Symposium on Current trends in Wetlands and Fisheries in the New Millennium, 8-9, Nov 2000, Assam University, Silchar :2.
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    • ADDRESS first topic previous topic

    1.) Department of Zoology,
    Gauhati University,
    Guwahati-14,
    India.

    2.) Department of Life Sciences,
    Assam (Central) University,
    Silchar-11,
    India

    3.) Division of Tissue Culture,
    National Institute of Virology,
    Pune-1,
    India.