Principles of Aquaculture
Diagnostics
Dr. Craig Kasper
FAS 2253
Fall 2006
Introduction
•
Readings from Chapters 1-5 of Noga
(1996)
1. 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)
Introduction
2. 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.
Introduction
3. 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).
Introduction
4. 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!
Introduction
5. 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.
Introduction
6. 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!!
Introduction
Acute multifocal necrotizing supperative hepatitis
Time
location
dead
cells
neutraphils
inflammation
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?
Introduction
6. 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.
Introduction
6.
The 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
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 size
Number of fish to
sample
50
100
35
45
250
500
50
55
>2000
60
*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
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•
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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
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•
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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.