All living beings, in their natural surroundings, become susceptible to diseases one time or the other in their life.

Fishes and shellfishes are also no exception.Even in the natural conditions, a few of fishes and shellfishes become diseased and most of the cases pass unnoticed possibility due to lack of interest

Pillai, C Thankappan

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Fish and Shellfish Diseases in Culture Systems IV. Bacterial diseases C. Thankappan Pillai Central Marine Fisheries Research Inst itute, Cochin· 18 "Disease may ensure immunity but not life" All living beings, in their natural 'surroundings, become susceptible to dis· eases one time or the other in their life. Fi shes and shellfishes are also no excep-tion. Even in the natural conditions, a f ew of fishes and shellfishes become dis-eased and mos t of the cases pass "'nnoticed possibility due to lack o f inter-est and and/or odservation. Ocuurrecce ·of diseases in these organisms either in thei r natural envi ronments Or in cu lture system adversely affect the population. So, a thorough study of th e diseases is absolute ly essent ia l, espec ially in the present context of a global aware-·cess to enhance the food production through aquaculture of f ishes and shellfishes in order to ineet the requirements of anima l protein for the increasing population. Considerable work has been carried out in severol countries in this field .and substan tial l iterature is availab le (Conroy and Herman, 1970; Sinder-m ann, 1970 and 1977, Snieszko , 1970; Bullock, 1971; Bullock; Conroy and Snieszko 1971 ; Mawdesley - Thomas, 1972; Reichenback - Klinke, 1973; van August, 1981 . Duijn , 1973, Roberts and Shepherd. 1974; Ribelin and Mijaki . 1975; Dulin, 1976; Hoffman, 1977; and Roberts, 1978) . . Ho weve r, fe w investigations have been undertaken rn th!s disc ipline in our country and it is imperative that concerted efforts should be made to study and underst and the various important fish and she llfish diseases affecting our resources. Some important bacterial diseases, which cause heavy los, to cu lti vabl e· species of fi sh and she llfishes are: 1 . Hemorhagic sep ticaemia 2. Vibriosis 3. Furunculo sis 4. Eye disease 5. Fin / tail rot 6 . Ulcer 7 . Skin les io n 8 . Myxobacteriosis 9. Kidn ey d isease 10. Gill rot 11 . Tuberculosi s 12. Enteric bacteriosis Fish and shellfihh es being mute and living in a dynam ic envi ronment, 19 ·detection and disease diagnosis in these cultivabl e species are rather difficult as compared to that of human diseases. The symptoms of a disease are ·of considerable help to privisionally diagnose the case. But, detection of the aetiological agent of the disease will be of definite hope to confirm the case and makes it easier to treat the disease :prophylactic outbreak. as well as to sdopt proper measures against its Nevertheless, symptomatic treat-:ment shall be followed as any delay in treatment results in heavy mortality ·of the afflicted population. Consider-ing the needs, a provisional key, for the diagnosis of cases and treatment, .is formulated and presenied in table 1. Bacterial diseases predominate .among fishes and shell-fisees. But, it may be surprising to note that these -organisms are not necessarily essential to be the cent percenr cause(s) always 'for an outbreak of disease. Because, in any community, it has been detected that normal individuals I hosts also sometimes harbour or carry potentially pathogenic microbes without showing any apparent disease symptoms or ,falling sick. For example, species of Aeromonas and Pseudomonas which are the normal bacteria of the aquatic environments cause diseases to the fishes and shelifishes when they are 'under stress. Any sort of stress (eg. dense population) explicates the {;hances of invading organisms to make the host more susceptible and provokes diseases. And, this happens due to failure of the host's defense mechanism in ' the struggle against the invading August, 1981 agent. Here, it is better to real ise that stress always lowers the resist ance of anima is and enhances suscepti b ilty to disease. 'Stress' · is a state of condition, caused by intrinsic or extrinsic factors, which upsets the adaptive responses of the animals and reduse the chances of their surv ival. Stress can be short term or chronic . In the case of short term stress (eg. cold shock) the animals return to normalsy within a few (4 - 8) hours. But chronic stress cause seve.re damage as a result of increased susceptibility to infections probably because of reasons such as decreasing inflamma-tory respon ses (basic protective responses to tissue damage). decreasing amount of circulating lymphocytes (white blood cells responsible for immune responses). Impairing of gamma - globuling (plasma pro t ein concerned with . antibody production against infections) production and depressing interoferon (important defe-nsive factor against virus infection) production etc. Thus it is essential to maintain the natural equilibrium to a resonably possiole level among the host, para-site and envoronment to minimise diseasas Outbreak of adisease is usually the result of abnormal alternation in the adjustment of the interrelationship of the host: parasite and environment and the seventy of the disease depends on the intensity of the alteration. Hence, enough care has to be taken in sele-cting dis ease-free and immunised seed, observing hygienic measures, . main-taining congenial water and other ' sanitary conditions, and supplying; suitable balanced diet for having, healthy and quality fishes and shell-· fishes. 21 SI. No. 1 . 2. 3. Disease Hemorrhagic sept icaemia Vibriosis Fu runculosis Clinical symptoms Body reddening, sk'in lesion with pus and/or blood, swollen belley, protruding scales, sun-ken or ptotruded eyes inflamed anus, bloody discharge from the vent, discolourstion and degeneration of . the . I.iver, swollen spleen, inflamed swim .. bladder, qnaemia. Erythemia or hyperemia of the skin and fins, pete-chiae in the mouth, swimming with uneasiness . near water surface, body darkening, abdo-minQI distension, corneal 'opa-city, anorexia, pale gills, enlargement or liquefaction of the spleen and kidney myo-cardial infection. Boils may be presart, skin lesion with pus/or blood, pale gills, sluggish , movements, fraying of the fins, inflamed intestine, myocardial necrosis, iiquefaction of the kidney and spleen, bleeding from the gills. Drug(s) Chloromycetin Terramycin - do -Terramycin Administration Shari bath in suitable water' having any one of the drugs at a rate of 25 - 75 mg . per liter of watar OR intraperito-neal inject ion of anyone of the drugs at a level 0 .02 mg. per gram body weig4t of the fish or anyone of the drugs may be given along with feed, at a rate of 1 mg. per 10 gram body weight of the fish, once daily for 7 - 21 days. - do ·-Along with feed, the drug may be administered at a rate of 5 -10 mg. per 100 gram body weight of the fish once daily for 7 - 21 days OR in-traperitoneal injection of the drug at a dose of 0.02 mg . per gram body weight of thefish. SI. No . Disease 4 . Eye disease 5. Fin I tail rot 6. Ulceer 7. Skin lesion TAB L E - 1 (Coniinued) Clinical ~ymptoms Eye opacity with tissue prol i-feration, weak movements, pale gills, anorexia . Loss of natural colour begin-ning f rom the out margin of fin I tail " fraying of the fin I tail , progressive disintegration of the fin ! tail tissue, weak movements , . swimming near water surface. EcchYlT'osis may be noti~ ed . Shallow open sores mostly with white rim, presence of pus and I or blood, erdoded fins and mouth ' Skin lesion clearly visible in water, pus and I or blood in the lesion, s,luggishness, anO-rexia : Orug(s) Brilk,mt green Chloromycetin Acriflavine Acriflavine Chloromycetin Acriflavine Brilliant green ChlQromycetin Administration One mg. of chloromycetin may be given in feed per 10 gram body weight of the fish, once daily for 21 days . Swabbimg with brilliant green solution (0 .1:%, ) at the area with or without surgical remo-val of the infected t issue . Dip in 1 - 5 ppm acrjfl avine suitable water or surgical removal of the infected tissue and application of the drug (0 .1%) in solution in the operated area . One mg . of chloromycetin may be given in feed per 10 gram body weight of the fish once daily for 7 - 21 days. Swab-bing with acriflavine (0.1 ~; ) solution at the site of infec-tion. Swabbing either with acrifla-vine or brilliant green (0 .1%) solution at the site of infection OR short bath thrice daily in ~~ital;>l~ wat~r havinlj the SI. No. 8. 9. 10. Disease Myxo-bacterious Kidney disease Gill rot ; "' TAB L E - 1 (Continued) Clini ca l Symptoms Grayish whi t e spo ts or patches in the body and f ins with pus and f or blood, swo llen lips, anorexia, sluggishn ess, dama-ged gill tissue. Body lesion, bilateral expo-th al mia, swollen abdomen, ba lanceless sw imming, body d arkenin ing , swollen kidney , swo ll en sp lean, infected li ve r, pericarditis, fal se membrane over kidney, liver and spleen may . be noticed . Iso lated movements, anorexia restl essness , surface floating. orientation against the current, weakn ess, gill tissue decay or proliferation , Drug(s} Terramycin Erythromycin Copper Sulphate Erythromycin Administration antibiotic at a rate of 25-75 mg, per litre of water for 3 - 10 days. One mg. of the drug in feed , per 10 gr"m body we ight of the fish , once daily for 7-21 days OR shorr bath having the drug in suitable water at a dose of 25 - 75 mg. per liter of waterfor 7 - 21 days. - do -One mg . of the drug (erythro-mycin) in feed, per 10 gram body weight of the fish , once daily for 7 - 21 days OR dip treatment (for few seconds) in copper sulphate in suitable water at a rate of 1 - 2 m(J. per liter of water , SI No. Disease 11. Tube lculosis 12. Enieric bacteriosis TAB L EO - 1 (Continued) . Clinical symptoms Progressive body weakening, damaged or folded fins,swelling of abdomen, anorexia, colour fading , deformities in the skeletal system, sluggish movements, opacity in the cornea, scale defects listless-ness, presen ce of tubercles. Enteritis, sluggish movements, body lesions, body discolour-ation, reddening of the anus, cyclic movements. swimming near water surface. Kidney may be ihfected. Drug(s) Kanamycin Sulphadizine Sulphisoxazole Administration One mg. of the drug in feed, per 10 gram body weight of the fish, once daily for 7-21 days DR intraperitoneal injec-tion of the drug at a rate of 0.02 mg. per gram body weight of the fi sh. One mg. of sulphisoxazole in feed, per 10 gram body weight of the fish, once daily for 7 - 10 days OR short bath, having sulphadiazine in suit-able water at a rate of 25-75 mg. per liter of water, for 3 -14 days. • Habitat water or water similar in quality to that of habitat water should be us,d. 

Fish and shellfish diseases in culture systems IV. Bacterial diseases

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Fish and shellfish diseases in culture systems IV. Bacterial diseases

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