Disease means…………deviationfrom normal condition eitherbehavioral, structure or physiologicalstateYou must know normal condition todetect abnormal one……………….easily to be done bycontinuous observation
The aim of diagnosis process todetermine the accurate cause of thedisease the select the proper treatmentThe owner should be advised to bringboth the fish (live and freshly dead )and a water sample in separate cleancontainers.
Steps of diagnosis• Case history• Clinical signs• PM exam• Lab exam (Parasitological, Bacterial, Mycological, Virological and water quality)• Histopathological exam• Molecular methods to detect and characterize the agent’s nucleic acid• Biological test
I – Case History1)Fish2)Environment A) Rearing unit B) Water
a) Recent rates Water problem O2 or toxicb) Time ….early Has considerable morbidity morning or suddenc) Species Chronic or parasitic especially when affect some species involvedd) Size and age of dead fish
• All run facilitiesb)Sudden change in routine managementb) Usual routine for feeding as well Change in diet quantity, quality or forms. (fry, fingerlings or broad stock). As well source and protein percentages.
c) prior treatments, includingmedications, have been given.• Abnormal behaviour or functionof fish
2) Environment A) Rearing unit• Type, size and location of the facilities
2. System of fish management3. Stocking rate /stocking time
7. Habitat utilization …weeks ???8. The surrounding of rearing unite…human habituations, neighborinfected farm
B) Water1) Water source: sewages, underground water or surface water.
2) Water exchange rates3) Physical examination of water- color and transparency… algae…- turbidity- smell…..amonia…..organic matter
4) Chemical examination of water-Dis O2- Ammonia, nitrite,- pH………..acidic……Branchyomycosis- Hardness……….soft water……Deedisease- heavy metals
II-Clinical sign 1- Behavioural Examination General Exploration• If a client submits live fish to the clinic, aeration should be immediately placed into the container that holds the fish.• (Examination of fish in water)
2- escape reflex 3- sick fish easily caught4- position of fish….TB
• flashing or itching (rubbing against objectssuggesting skin problems)• piping (staying near the air - water interface toobtain more oxygen, suggesting gill problems)• Sick fish may exhibit other behavioral signs,including staying near the surface of the water= respiratory distress• Extremely sick fish may be in dorsal or lateralrecumbency.
•scraping the body or holding the ﬁns close to thebody ( “ clamped ” ) because of parasite irritation•showing various behavioral abnormalities•Sick fish often congregate together, separatingthemselves from healthier• Different fish species inhabit different parts of thewater column (surface, bottom, shoreline, etc.), andthis position often changes with sickness.
Clinical Examination* Precautions during examinations 1. Fish should be carefully handled 2. Not allow fish to come in contact with hard objects that affect slim 3. Examine fish on moist substances 4. Examine in shade and avoid wind to prevent dryness 5. You examine by naked eye, stereo microscope or magnifing lence.
2- External examination: - small fish can be examined atmoist palm, small plat
- large fish put on their rightside on moist glass or plasticdiaper. Put fish on their rightsides and held them by lefthands. Save eyes with palm ofhands and with other handssupport tail.
* Body inspection1- color of the body• Sick fish are often abnormally colored, comparedwith the healthier• Fish in breeding condition often have more brilliant colors than nonbreeding fish• Darkness over whole body…..chronic disease, bad water quality
Parasites or other irritating conditions may also elicit a thickening of theskin, leading to a whitish or bluish skin color. This change might behighly localized (pinpoint to larger foci) or cover nearly the entire body
local tissue irritation/damage, such as parasite feeding,
chronic wounds, or healing wounds, which cause a change in the pigment cell distribution at that site
5- abnormalities in the vertebral column, mandible, nose…
Streptococcus swollen vent, hemorrhage8- abnormalities in anus, uorogenital opening or operculum
Special histological / Cytological techniques1- Immunohistochemistry (IHC) / Immunofluorescent chemistry (IFC)Enables identification of agent or altered cell receptor expression in relation to localization within the body and within the tissue and in relation to alterations in histomorphology. Therefore, it facilitates the understanding of potential pathogenicity.3 - Electron microscopy
VI. Laboratory exam(Parasitological, Bacterial, Mycological, Virological) Start by killing of the fish by one of the following methods 1- cut spinal cord 2- over dose of anesthesia 3- electric current 4- Catch the fish with dry towel and hit to hard object Not use chemicals in killing of fish especially in bacteriological examination
VII. Molecular methods1. Polymerase chain reaction (PCR)The PCR reaction is ideal for detecting thepresence of bacterial, viral, parasitic(protozoal or metazoal), or fungalpathogens. The principle of detection is toattempt PCR with primers that arecomplementary to a part of the genome ofthe pathogen, but not of the host.
1.1. Conventional PCR protocols are for thedetection and identification of DNAsequences1.2. Real-time Taqman® PCR is a variation ofconventional PCR. This type of PCR can beused to detect and quantify the load of aninfectious agent in clinical samples. It candetect RNA or DNA sequences.1.3. reverse transcriptase PCR (rtPCR)protocols are for the detection andidentification of RNA sequences (RNAviruses, bacteria).
General lines1- DNA or RNA will be extracted from the samples2- PCR reaction mix contains specific primers3- replication in thermal cycler4- The resulting PCR mix will be analyzed usingelectrophoresis on a gel, to see if a band of the expected size
2. Restriction fragment length polymorphism (RFLP)/DNA fingerprinting• Used to identify a change in thegenetic sequence. Can be used totrace inheritance patterns, identifyspecific mutations, and identifybacterial strains
3. Microarray analysisUsed to detect gene expression. Itassesses the expression or activityof a specific gene of an organismby quantifying the amount ofmRNA the gene produces. notcommonly for the detection ofinfectious agents.
4. In-situ hybridization (ISH) • Detects presence and location of nucleic acids within lesions in order to establish a link between infection and disease. • Based on identified labled nucleic acid prob on histological sections prepared by modified method.
• Stress may be a result of: 1) Poor water quality 2) Poor nutrition 3) ______________ 4) Handling 5) ____________________What causes fish to get sick?
• Fish are generally more vulnerable to disease outbreaks during summer months because: 1) _____________________ 2) Dissolved oxygen 3) ______________________________ 4) Disease organisms are more active at warm temperatures What causes fish to get sick?
Behavioral: 1) Slowing or Cessation of Feeding 2) __________________ 3) Abnormal Distribution 4) __________________ 5) Lethargic Swimming Symptoms and signs of disease
Physical Symptoms and Signs • I. Gross External Signs: 1) Production of Excess Mucus 2) _______________________ 3) Eroded Fins, Gills, and/or Sores on the Body 4) _____________________________ 5) Swelling or Cysts on the Body, Head, or Fins 6) _____________________________ 7) Hemorrhages on Body Surface Symptoms and signs of disease
Physical Symptoms and Signs • II. Gross Internal Signs: 1) Discoloration 2) ______________________________ 3) Lesions 4) Changes in texture of Organs, Tissues, and Musculature 5) ________________________________ 6) ________________________________ Symptoms and signs of disease
• Three major patterns: 1) Mortality due to ______________ ___________________ 3) Mortality due to ______________ ___________________ 5) Mortality due to ______________ __________________ Mortality Patterns
Mortality(# fish) Mortality(# fish)A. B. 1 12 24 1 12 24 Time (days) Time (hrs) Mortality(# fish) C. 1 12 24 Time (weeks)