2. INTRODUCTION
Fish disease has become one of the most important factor for succe-
-ssful aquaculture management. It is essential to recognized various
diseases and health problems of fish in their culture practices often
causing mass mortality.
In India, the major carps and other groups of fishes are susceptible
To non infectious and infectious disease.
Non infectious disease are of relatively less occurrence and less impo-
-rtance but infectious disease are commonly caused by virus, fungus,
Bacteria, Protozoans and Metazoans.
Diagnosis of disease is very important for successful fish farming
operation.
CAUSE S OF DISEASE OUT-BREAK
There are different factors which causes disease in fishes like poor
Husbandary, over crowding, unsuitable water quality and dietary
Imblance.
Physical injurey due to rough handling & varies o2 levels, temperature
3. Fluctuation, inadequate nutrition and a verity of trorins in water used.
They produce stress and make the fish susceptiable to a variety of dise—
ease outbreak.
There are many steps involved in the proper digrames of fish diagnose of
fish disease as follow.
CIRCUMSTANTIAL DATA
When disease occurs, it is essential to collect information redarding the
affected area, nature of infection, whether the affected areas are in the
vicinity of agriculture field/industrial belt/sewage disposal system etc.
and whether disease occurred in these areas previously and the time of
occurrence and rate of mortality.
Collection and preservation of diagnostic fish samples:-
For reliable diagnosis, live fish sample with distinct clinical symtoms
should be collected which should be immediately examined.
Species, size and percentage of the diagnostic fish sample should be
carefully noted.
If immediate examination of the sample is not possible. The sample
should be preserved for isolation and identification of actiological
agents.
4. FOR BACTERIA, VIRUS AND FUNGUS :- Sample should be preserved by
chilling or freezing.
FOR PARASITE :- Sample should be preserved in 10% formalin.
FOR HISTOPATHOLOGIAL STUDIES :- Sample should be preserved in proper
fixative like 10% neutral buffered formalin.
OBSERVATION ON BEHAVIOUR AND CLINICAL SYMPTOMES OD
DISEASE SAMPLE :- Disease sample of fish shows some diagnostic behavioral
symptoms – which are to be recorded and these help in the diagnosis of disease.
PATHOMORPHOLOGICAL EXAMINATION :- General appearance like
healthy, stunted, emaciated or sickly appearance of the fish should be observed.
Pigmentation, visible signs on the body like hacmorrhages, patches etc should
be noted.
Gills, skin, fins should be examined for the presence of pathogen and errosion/
patches/haemorrhages etc.
PATHOANATOMICAL EXAMINATION :- Disease fish should be dissected and
the viscera should be examined i.e. organs like liver, spleen, kidney, gut,
pancreases, air bladder should be examined for any abnormality in their colour
and consisting the presence of any haemorrhages, lessions/ inflamations ctc.
Squash preparation of these organs should be made and examined for the
presence of parasites/bacteria/fungus etc.
5. HAEMATOLOGICAL EXAMINATION :- From the live specimens blood
should be collected and various haematological parameter such as haematocrit
values differencial count, haemoglobin, total RBC and WBC count, must be
setimated.
Smear preparation of kidney, spleen should be made and examine under
microscope for parasites, bacteria and fungi.
ISOLATION AND IDENTIFICATION OF PATHOGENS :- For determining
the nature and type of pathogens involved in the diseased fishes specific studies
are required for isolating and identifying the pathogens.
BACTERIOLOGICAL EXAMINATION :- From the living dicrease fish swabs
should be taken from different organs and should be inoculated in suitable
media under ascqetic condition for subsequent isolation, identification and char-
acterisation of the bacterial agents involved.
VIROLOGICAL EXAMINATION :- Sample of kidney, liver, spleen and
gonads from diseased fishes are collected and processed for inoculation in the
monolayer fish cell line and their cytopathic effect CPE are studied.
Detection of virus can be made by electron microscopy of the infected
tissue.
PARASITOLOGICAL STUDIES :- Sample for parasites are to be collected
from diseased fish and should be preserved in 10% formalin for subsequent
studies. Sample for parasites should be taken from the living fish only, because
6. many parasites leave the host where they die.
EAXMINATION FOR FUNGAL PATHOGENES :- Sample of fungus are
collected from the disease specimen and should be cultured and isolated in pure
form in suitable media. If immediate examination is not possible then they
should be preserved in proper fixative 10% formalin for subsequent
examination
HISTOPATHOLOGICAL EXAMINATION :- Histopathology is the most
important tool for disease diagnosis. It confirms the involvements of etiological
Agents in the organs and tissue of diseased fishes and also describe the extent of
damages caused in various organs system. Details of histopathological
technique are as follow :-
Tissue sample are to be collected only from freshly killed speciemen. Small
bits of tissue (3-4mm thick) from different organs of diseased fishes are to be
collected and fix in10% neutral buffered formalin for 18-24hrs.
Fixed samples of tissue are to be processed through standard histological
methods involving treatments through grades of alcohal cleaning by xylol and
impregnation of processed tissue in wax making them ready for section cutting.
Wax impregnated tissue are then cut into thin sections (5-7 meu) by a rotatary
microtome and these sections, being mounted on clean glass slides are pread
proper.
Routine staining of the cut section is then done by haematoxylin & Eosin.
7. for parasites fungus, bacteria to confirm these pathogens in tissue section.
Permanent slides to be prepared and maintained for documentation and
publication of results of investigations through photo micrography of the
stained preparation.
ANALYSIS OF WATER QUALITY PARAMETERS :- When disease out-break
occurs in pond and tanks, it is necessary to collect water sample for analyzing
the value of its parameters i.e. co2, pH, alkalinity, turbidity, ammonia & nitrate
etc. and to examine whether these values are within the acceptable limits or
some of them have crossed the tolerance limits of fishes.
These abnormal parameters cause stress and magnify the risk of disease
outbreaks.
Therefore, while diagnosing any disease incidence water quality parameters
of affected ponds/tanks should be analyzed.
========================================THANKS========
