Principles of Aquaculture Diagnostics

Dr. Craig KasperFAS 2253Fall 2006

Introduction

• Readings from Chapters 1-5 of Noga Readings from Chapters 1-5 of Noga (1996)(1996)

1.1. What are diagnostic tests?What are diagnostic tests?

A series of tests designed to determine A series of tests designed to determine the health status of a healthy population of the health status of a healthy population of animals vs. that of a population of animals animals vs. that of a population of animals deemed unhealthy. (Healthy vs. sick)deemed unhealthy. (Healthy vs. sick)

Introduction2. Why should they be performed?2. Why should they be performed?

Often involves establishing a background or Often involves establishing a background or baselinebaseline information concerning the health of a information concerning the health of a population of animals, i.e. population of animals, i.e. parasite loadparasite load,, nutritional statusnutritional status, , bacterial exposurebacterial exposure..

Anything that is considered abnormal is also Anything that is considered abnormal is also known as a known as a lesionlesion..

Introduction

3. How should these tests be performed?3. How should these tests be performed?

Hopefully, under Hopefully, under strict guidelinesstrict guidelines using using quality quality controlcontrol and S.O.P’s with a list of written and S.O.P’s with a list of written procedures! But doesn’t always happen. procedures! But doesn’t always happen.

Look for American Association of Veterinary Look for American Association of Veterinary Laboratory Diagnosticians accreditation Laboratory Diagnosticians accreditation (ADVLD).(ADVLD).

Introduction4. Who is qualified to perform these tests?4. Who is qualified to perform these tests?

a. Two issues should be addressed here, esp. if you are the one a. Two issues should be addressed here, esp. if you are the one performing the tests.performing the tests.

i. i. MoralMoral = Can I do it? (I might actually have the skills.) = Can I do it? (I might actually have the skills.)

ii. ii. LegalLegal = Am I licensed to do it? (Can I testify in court? Am = Am I licensed to do it? (Can I testify in court? Am I liable if I am wrong? Rem: drugs, pharmacy, licenses, etc.I liable if I am wrong? Rem: drugs, pharmacy, licenses, etc.

What would I need? DVM, Ph. D., affiliation with university or What would I need? DVM, Ph. D., affiliation with university or organization (lab), ACVP, Diplomate, AFS –pay dues for being a organization (lab), ACVP, Diplomate, AFS –pay dues for being a fish health inspector! fish health inspector!

Introduction

5. What should be included in the diagnostic 5. What should be included in the diagnostic evaluation?evaluation?

a. Animalsa. Animalsb. Facilitiesb. Facilitiesc. Environment, i.e. water quality, feed c. Environment, i.e. water quality, feed d. Questions for the producer/owner! d. Questions for the producer/owner! May be the most important piece of information.May be the most important piece of information.

Introduction6. What 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!!

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?

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.

Introduction6. The clinical evaluation

a. Historyb. Physical Examinationc. Clinical Signsd. Gross lesionse. Cytologic evaluationf. Biopsyg. Necropsyh. Ancillary testing

bacteriologyvirologyToxicology (water and animal samples)Clinical pathology (serum chemistries,

hematology)j

Introduction

7. Sample sizes and inferences about a population based on samples.

Must have sufficient number or diagnosis is meaningless.Over-interpretation Under-interpretation

Statistics: Sampling Size*Lot sizeLot size Number of fish to Number of fish to

samplesample

5050100100

35354545

250250500500

50505555

>2000>2000 6060

*Based on assumed 5% prevalence level in the population.*Based on assumed 5% prevalence level in the population.

Symptoms vs. Signs

• Symptoms: 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.

Common Clinical Signs

• Anorexia• Flashing• Piping• Lethargy• Erratic Swimming Patterns• Isolation• Loss of Fright Response

Lesions vs. Pus, Crud or Goop?

• A lesion simply stated is…any abnormal (unhealthy) tissue.

• Lesions may contain purulent exudate, hemorrhage, necrotic muscle, etc.

Examples of Lesions

• Ascites• Exophthalmia• Hemorrhage and/or congestion• Cutaneous erosions and ulcerations• Gill necrosis• Abscesses• Granulomas

DO CLINICAL SIGNS & LESIONS ALLOW YOU TO

MAKE A DIAGNOSIS?

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.