Principles of Aquaculture Diagnostics

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Principles of Aquaculture DiagnosticsDr. Craig Kasper FAS 2253 Fall 2006

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IntroductionReadings from Chapters 1-5 of Noga (1996) What are diagnostic tests? A series of tests designed to determine the health status of a healthy population of animals vs. that of a population of animals deemed unhealthy. (Healthy vs. sick)

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Introduction2. Why should they be performed? Often involves establishing a background or baseline information concerning the health of a population of animals, i.e. parasite load, nutritional status, bacterial exposure. Anything that is considered abnormal is also known as a lesion.

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Introduction3. How should these tests be performed? Hopefully, under strict guidelines using quality control and S.O.P’s with a list of written procedures! But doesn’t always happen. Look for American Association of Veterinary Laboratory Diagnosticians accreditation (ADVLD).

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Introduction4. Who is qualified to perform these tests? a. Two issues should be addressed here, esp. if you are the one performing the tests. i. Moral = Can I do it? (I might actually have the skills.) ii. Legal = Am I licensed to do it? (Can I testify in court? Am I liable if I am wrong? Rem: drugs, pharmacy, licenses, etc. What would I need? DVM, Ph. D., affiliation with university or organization (lab), ACVP, Diplomate, AFS –pay dues for being a fish health inspector!

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Introduction5. What should be included in the diagnostic evaluation? a. Animals b. Facilities c. Environment, i.e. water quality, feed d. Questions for the producer/owner! May be the most important piece of information.

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IntroductionWhat is the final outcome of the diagnostic? What should the lab tell you? “Your fish have a clear case of acute multifocal necrotizing supperative hepatisis!” WHAT??? Translation PLEASE!!

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IntroductionAcute multifocal necrotizing supperative hepatitis Time location dead neutraphils inflammation cells of the liver “A rapid onset of dead white blood cells throughout an inflammed liver, put simply your fish have bacterial hepatitis!”Why didn’t you just say so?

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Introduction6. What is the final outcome of the diagnostics? a. Morphological Diagnosis (only?) b. Recommendations re: husbandry? c. Treatment recommendations? d. Changes in facilities, environment? e. LABS WON’T PERFORM TESTS TO DETERMINE IF FISH ARE SAFE FOR HUMAN CONSUMPTION.

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IntroductionThe clinical evaluation a. History b. Physical Examination c. Clinical Signs d. Gross lesions e. Cytologic evaluation f. Biopsy g. Necropsy h. Ancillary testing bacteriology virology Toxicology (water and animal samples) Clinical pathology (serum chemistries, hematology)j

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IntroductionSample sizes and inferences about a population based on samples. Must have sufficient number or diagnosis is meaningless. Over-interpretation Under-interpretation

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Statistics: Sampling Size**Based on assumed 5% prevalence level in the population.

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Symptoms vs. SignsSymptoms: Description of how an individual feels to a proessional health care specialist. Why doesn’t this work for aquatic critters? Clinical signs: Observation of behavior of non-healthy animals.

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Common Clinical SignsAnorexia Flashing Piping Lethargy Erratic Swimming Patterns Isolation Loss of Fright Response

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Lesions vs. Pus, Crud or Goop?A lesion simply stated is…any abnormal (unhealthy) tissue. Lesions may contain purulent exudate, hemorrhage, necrotic muscle, etc.

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Examples of LesionsAscites Exophthalmia Hemorrhage and/or congestion Cutaneous erosions and ulcerations Gill necrosis Abscesses Granulomas

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DO CLINICAL SIGNS & LESIONS ALLOW YOU TO MAKE A DIAGNOSIS?

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NO! Clinical signs and lesions suggest to you the possible disease processes. The diagnosis can only be “made” by isolating or demonstrating the presence of the pathogenic organism with a concurrent disease process.

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Last Updated: 8th March 2018

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