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Questions and Answers
Why is sanitation and disinfection important during the quarantine of fish?
What is a common early sign of disease in fish?
What method can be used to examine fish for parasites?
What role does the client play in diagnosing fish diseases?
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When should sampling of quarantined fish be conducted?
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What type of adjustments might clients be asked about regarding the fish environment?
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What type of diagnostic information can be obtained from blood culture in fish?
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What should be observed throughout the quarantine period for fish?
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Which behavioral sign indicates a sick fish?
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What is a physical sign of a sick fish?
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What should be checked first when sick fish are suspected?
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Which water quality parameter is critical to check for suspected sick fish?
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What does rubbing against objects indicate in fish?
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What condition is indicated by a distended abdomen in fish?
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Why should records be kept in a fish farming operation?
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What role do colorimeters play in fish health management?
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What is the recommended cooking temperature and time to effectively kill parasites in fish?
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Which method is commonly used for the detection of parasites in fish flesh?
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What should be done with visibly infected fish before marketing?
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At what freezing temperature and duration should fish be treated to kill parasites?
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Which of the following is NOT a common handling step performed by processors?
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What is the primary focus of inspections conducted on eviscerated fish?
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What does biosecurity in aquaculture aim to reduce?
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What factor can affect the successful detection of nematode larvae using the candling method?
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What role does pathogenicity play in pathogen management?
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Which type of pathogens are Aeromonas and Vibrio classified as?
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Why can some pathogens be difficult to diagnose?
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What practice is essential for effective disease control?
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What is a consequence of repeated and incorrect drug application in aquaculture?
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What is the recommended dose range for sodium hypochlorite as a disinfectant?
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Which of the following statements about viruses is true?
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What is the contact time required for the effective disinfection using sodium hypochlorite?
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Why is it beneficial to observe a patient fish in its home environment?
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What may indicate respiratory compromise in fish?
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Which behavior is commonly seen in fish infected with external parasites?
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During the observational examination, what should be documented besides abnormal behaviors?
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What is the purpose of using general anesthesia during a physical examination of fish?
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What unusual sign is typically associated with fish exhibiting respiratory issues?
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What might be one of the first signs that a fish is sick?
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Why is it important to inspect the patient's living quarters during the observation?
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Study Notes
Behavioral Signs of Sick Fish
- Sick fish may stop eating or respond poorly to food, appearing lethargic. Healthy fish typically eat aggressively at feeding time.
- Sick fish might hang in shallow water, gasping at the surface for oxygen. Pond fish are usually only visible during feeding.
- Rubbing against objects or pond walls suggests a problem like parasites irritating the skin.
- Flashing behavior in the pond is another indicator of illness.
Physical Signs of Sick Fish
- Sores (wounds, ulcers, hemorrhages) on the body.
- Ragged or frayed fins.
- Abnormal body shape, such as a swollen abdomen ("dropsy") or bulging eyes ("Popeye").
- Loss of mucus.
- Loss of scales.
Diagnosing Sick Fish: Water Quality & Record Keeping
- Check water quality parameters: dissolved oxygen, ammonia, temperature, nitrite, pH, total alkalinity, total hardness, and conductivity. Use test kits or meters.
- High ammonia levels are especially dangerous, particularly with overcrowding.
- Maintain daily records of stocking dates, fish size/age, source, feed type/rate, growth rate, mortality, and water quality. These records are vital for diagnosis and treatment. A complete case history is needed, including these records and any treatments attempted.
Food Hazard Reduction Measures
- Reduce parasites during harvesting/processing. Special handling includes reducing parasite numbers and inactivating them through heat or freezing.
- Heat treatment: above 60°C for at least 1 minute.
- Freezing treatment: -20°C for 24 hours or -35°C for 15 hours (except for trematodes).
- Prevent marketing of heavily infected fish by reducing infection levels or removing visibly infected fish. Good hygiene and screening are crucial.
- Processing steps potentially impacting parasite levels: heading, gutting, filleting, skinning, trimming.
- Inspection for parasites should focus on the abdominal cavity, liver, and roe (for consumption). Inspect fillets/slices during trimming and after processing.
- Candling (examining fish on a light table) is a common detection method, but its effectiveness varies depending on fillet thickness, presence of skin, oil content, pigmentation, and operator expertise.
Biosecurity and Quarantine Procedures
- Biosecurity reduces the risk of introducing and spreading infectious diseases within and between aquaculture facilities.
- Consult a fish health expert for disease diagnosis and management.
- Pathogenicity: Understanding how pathogens cause disease is vital for control. Some are opportunistic (affecting stressed fish or those in poor water quality), while others readily infect susceptible species.
- Diagnostics: Routine tests can identify many pathogens; some are harder to diagnose due to low numbers or hiding within the host. Environmental factors like temperature can impact diagnostic test results.
- Disease control: Sanitation, disinfection (use correct concentration and duration), and drugs can control disease. Preventive practices and vaccination are crucial, especially for viruses. Overuse/misuse of drugs can lead to resistance.
Chemical Disinfectants in Aquaculture
- Chlorine (Sodium hypochlorite): 200-500 mg/L for 10-60 minutes.
Quarantine Procedures
- Isolate incoming fish. Use sanitation and disinfection to prevent cross-contamination.
- Observe fish for normal/abnormal appearance and behavior (swimming, feeding, lesions). Loss of appetite is a common early sign. Good nutrition enhances disease resistance.
- Sample fish at the beginning and end of quarantine, and whenever disease signs appear. Examine skin, fins, gills (microscopy for parasites), and use blood cultures (bacterial infections). Use the results to improve quarantine methods and treatment.
Diagnosing Fish Diseases: History & Examination
- Detailed history is crucial: species affected, clinical signs, disease duration, treatments attempted (chemicals, antimicrobials, etc.), environmental changes (temperature, salinity).
- Observe fish in their natural environment if possible (tank, pond). Note interactions with other fish, behaviors (e.g., isolating, congregating near water outlets, at the surface for oxygen).
- "Flashing" (rubbing against surfaces) suggests external parasites; increased opercular rate and "piping" (gaping at the surface) indicate respiratory problems.
- Document behavioral abnormalities, color changes, and lesions.
- Direct physical examination under anesthesia is needed for a close assessment of abnormalities. Anesthesia also protects the practitioner.
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Description
This quiz covers the behavioral and physical signs of sick fish, including changes in feeding habits, symptoms like sores and abnormal body shapes, and water quality diagnostics. Test your knowledge on identifying and addressing health issues in fish.
