Chap 10 Presentation

8/8/2019 Chap 10 Presentation

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Diagnostic TechniquesDiagnostic Techniques

LAT Chapter 10


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Chapter 10

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Chapter 10

To Make A DiagnosisTo Make A Diagnosis

Diagnosis responsibility of veterinarian. Diagnostic tests may be performed by a technician.

Diagnostic techniques, history, clinical examination,

and other information considered.

Also used to define or establish health status of a

clinically normal animal.

Diagnostic techniques: radiography, anatomical

pathology, necropsy, microscopic examination oftissue sections, clinical pathology, microbiology,

hematology, blood chemistry, immunoserology,

parasitology and urinalysis


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Chapter 10

Anatomical PathologyAnatomical Pathology

Study of structure of diseased tissues

Gross pathology performed at necropsy.

Perform necropsies as soon after death as possible.

Animals that cannot be examined immediately should be

refrigerated, but not frozen, to slow the process of decomposition. Proper protective clothing must always be worn while

conducting a necropsy.

Good necropsy has consistent, thorough, routine method

for examining the entire carcass. Examine exterior of animal. Open abdomen and each internal

organ is examined in a specific order. Next the thorax is opened,

and heart and lungs are observed.

Make a precise record of each tissue collected and label each

container accurately with the types of tissues, date of collection

and name of investigator.


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Chapter 10

NecropsyNecropsy

Collected tissues are preserved by placing

them in a solution of 10-percent buffered formalin.

Stops all tissue decomposition and fixes the tissue to preserve its

anatomical structure.

Place remains in leak proof bag and barrel.

If radioactive or infectious, store and dispose of separately.

Mark containers with hazardous material involved.

Once fixed, slices of tissue are cut and placed in trays. Next they are treated with a number of chemicals, and then

embedded in paraffin.

Slices mounted on slides and stained with dyes.

Procedure is referred to as histopathology (histo = tissue).


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Chapter 10

Clinical PathologyClinical Pathology

Analysis of blood, urine, feces,

tissues, and exudates

Diagnostic microbiology to isolate and identify

microorganisms, interpret culture results, and perform

antibiotic sensitivity tests

Sterile swabs of various types are used for collection of

cultures from the area that is thought to be infected.

Throat swabs - dont touch lips, tongue, or other oral surfaces.

When culturing wounds or abscesses, obtain sample

from the edge, or wall, of the lesion.

Fresh feces for microbiological examination should be

collected in a clean container.

If feces not available, a rectal swab is acceptable but less ideal.


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Chapter 10

Bacterial CultureBacterial Culture

Prevent drying of the sample or swab.

Ampule at bottom of culture container is crushed to release fluid

transport medium to keep bacteria alive for 24 hrs.

Sample is inoculated for culture and identification.

Individual colonies are picked and grown as a pure culture.

Tentative ID made based on colony shape and staining.

Definitive ID requires biochemical, serological, and various tests.

Antibiotic sensitivity

Organisms inoculated over the surface of petri dish then several

small disks containing various antibiotics placed on surface.

If sensitive to a particular antibiotic, growth will be inhibited

around that particular sensitivity disk.

Supplies information for prescribing proper antibacterial therapy.


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Chapter 10

HematologyHematology

Blood = erythrocytes (red blood cells),

leukocytes (white blood cells), platelets, and plasma

Total blood volume = ~ 68% of body weight.

B

lood cell structures and normal ratios providesinformation to evaluate health status.

Reptiles, amphibians, and birds all have nucleated

erythrocytes.

Rabbits and guinea pigs have neutrophils with redstaining granules in the cytoplasm that make these cells

appear more like the eosinophils of dogs.

Some guinea pig lymphocytes also contain large, red-

staining granules called Kurloff bodies.


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Chapter 10

Blood CollectionBlood Collection

Red blood cells ruptured (hemolysis)

during collection by pulling too hard during aspiration, or

by forcing blood in a syringe through a needle.

Can result in inaccurate values for clinical chemistry tests.

Insert the needle bevel up to ensure smooth entry into the vein.

Syringe plunger pressure just sufficient to pull blood in.

Needle held firmly while attaching vacuum vial to prevent the

needle from pulling out or being pushed through vein.

Large animals - collect from veins on legs or from jugular.

Mice / rats collect small amount of blood from the tail

vein, heart or retroorbital.

Rabbits - collect from the vessels in the ear.


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Chapter 10

Blood CollectionBlood Collection


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Chapter 10

Serum & PlasmaSerum & Plasma

EDTA, sodium citrate or heparin prevent clotting, which

allows whole blood to be separated into plasma and the

red cells, white cells and platelets.

Whole blood will separate into clotted and a liquid fraction.

Some tests require whole blood, others require serum or plasma.

Red (orange) stopper indicates no anticoagulant.

Used to collect blood that is going to be allowed to clot.

Purple (lavender) stopper indicates EDTA.

Prevents clotting and allow the collection of plasma.

Green stopper indicates heparin.

Centrifuge spins tube very rapidly and forces the cells or

clot to bottom, separating liquid from cellular fractions.

The liquid (serum or plasma) can then be removed.


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Chapter 10

Blood Diagnostic TestsBlood Diagnostic Tests

1.Packed Cell Volume (PCV) = hematocrit, is a measure of

the % of cells vs. liquid in the sample.

2. Differential Leukocyte Count is a count of different types

of leukocytes in a drop of whole blood.

3. Total Red and White Cell Counts

When a diagnostic laboratory receives a request to

perform a Complete Blood Count (CBC) on a blood

sample, the lab will do all of the tests listed above, plusseveral more not mentioned here.

Clinical chemistry tests help to determine that the kidney,

liver and other organs are functioning normally.


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Chapter 10


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Chapter 10

Blood ChemistryBlood Chemistry

Accuracy of tests depends on method of collecting and

transporting specimen.

If whole blood or plasma is required, sample is immediately

mixed gently with a anticoagulant.

If serum is required, the sample is allowed to clot.

Proper withdrawal and submission procedures =>

uniform, representative specimens.

Tests for renal (kidney) function include analysis for

blood urea nitrogen (BUN) and creatinine.

Waste products produced during normal body metabolism.

These waste products are eliminated mainly by the kidneys, and

elevated blood levels of either one usually indicates an

abnormality in the urinary system.


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Chapter 10


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Chapter 10

Blood Chemistry (continued)Blood Chemistry (continued)

Chemical tests of liver function include metabolic tests,excretion tests, and serum enzyme tests.

Some substances formed in the liver are bile pigments, albumin,

fibrinogen, prothrombin, and cholesterol.

Excretion tests involve intravenous injection of dyes. At a standard time after injection, blood level of dye is measured

and excretion rate calculated.

Enzymes in high concentration within the cells of the liver.

When damaged, enzymes are released into the blood stream.

Serum ion levels important in disease diagnosis and

postsurgical treatment.

If uncorrected, severe illness or death may result.

sodium (Na), potassium (K), magnesium (Mg), calcium (Ca),

phosphorus (H

PO4), and chloride (Cl)


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Chapter 10


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Chapter 10

ImmunoserologyImmunoserology

Disease agents act as antigens (immune system

stimulators) => protein molecules called antibodies.

Antibodies in the serum indicate either an active

infection, or exposure to disease.

Serum antibody levels = antibody titer.

Techniques to measure antigen-antibody reactions

complement fixation, fluorescent antibody precipitation,

hemagglutination, and ELISA

Consecutive samples determine if antibody level is rising,

falling, or remaining constant.

An indication of the immune competence of the host, as well as

approximate stage of the disease.


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Chapter 10


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Chapter 10

Immunoserology (continued)Immunoserology (continued)

Viruses differ from bacteria mainly by being intracellular

and requiring living cells in which to grow.

Solutions containing cells known to support viral growth are used.

Once inoculated cells in the culture become infected,damaged or killed in characteristic patterns.

Testing tissues for the presence of DNA from specific

organisms is a means of identifying a disease.

A procedure called the polymerase chain reaction (PCR)

has made it possible to detect very small numbers of

organisms by artificially increasing (amplifying) the DNA

they contain.


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Chapter 10

ParasitologyParasitology

Therapy and prevention depend on accurate ID of a

parasite or parasite ova.

To detect helminth (worm) infections, fecal examination

for ova is performed.

Pinworms (Syphacia spp.), lay their eggs on the exterior

of animal around the anus.

Heartworm infestation of dogs and cats is diagnosed by

microscopic examination of the blood for microfilaria(immature larval forms).

External parasites, especially mites, may be identified by

microscopic examination of the fur or by skin scrapings.


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Chapter 10

Flea LifecycleFlea Lifecycle

University of Illinois Department of Entomology:http://www.life.uiuc.edu/entomology


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Roundworm OvaRoundworm Ova


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Pinworm EggPinworm Egg SyphaciaSyphacia speciesspecies


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Pinworm EggsPinworm Eggs

In The Uterus ofMature Adult


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Chapter 10

Male Adult PinwormMale Adult Pinworm

Syphacia mesocriceti


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Chapter 10

Hamster Skin MiteHamster Skin Mite (lateral view)(lateral view)

Demodex aurate.


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Chapter 10

Demodex aurate.

Hamster Skin MiteHamster Skin Mite (ventral view)(ventral view)


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Chapter 10

Isolated from Non-Human Primate

PsoregatesPsoregates Mange MiteMange Mite (ventral view)(ventral view)


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Chapter 10

Urine ExaminationUrine Examination

Physical, chemical tests + microscopic exam of sediment

culture and antibiotic sensitivity testing of bacteria isolated from

urine for diagnosing and treating bacterial infections

pH (acid or alkaline), specific gravity, color, and volume

Chemical tests detect mainly proteins, carbohydrates,

electrolytes, pigments, and hormones.

Urine sediment examination identifies cells, renal tubular

casts, and crystals.

Location of a disease in the urinary tract determined through

examination of the urinary sediment.

Important collection consideration:

Specimen must be collected in a clean, dry container.


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Chapter 10

Diagnostic ImagingDiagnostic Imaging

Bone absorbs X-rays, air absorbs very few X-rays.

The film directly beneath the bone appears white.

Film placed under the lungs appears dark or black.

Movement will cause blurring of the image and make

interpretation of the image more difficult.

Fluoroscope - X-rays of moving objects

X-rays are ionizing radiation.

Proper shielding worn by

personnel at all times.

Computerized Axial Tomography

Positron Emission Tomography

Magnetic Resonance Imaging

Ultrasound scanning


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Chapter 10

SummarySummary

Effective treatment can be initiated sooner if diagnostic

results can be made quickly available to the clinician

treating a disease outbreak.

The diagnostic techniques discussed above are equally

important in determining the true health status of normal-

appearing animals, since subclinical infections can have

devastating effects on research results.

It is through the combined use of these techniques,

coupled with clinical examination and daily observations

by laboratory animal technicians, that the health status of

both individual animals and entire colonies can be

accurately defined.


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Chapter 10

Summary (continued)Summary (continued)


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Chapter 10

Additional ReadingAdditional Reading

1. McCurnin, D.M. Clinical Textbook for Veterinary

Technicians. W.B. Sanders, Philadelphia, PA, 1994.

2. Pratt, P.W. Laboratory Procedures for VeterinaryTechnicians.Mosby, St. Louis, MO, 1996.

3. Sharp, P.E. and La Regina, M.C. The Laboratory Rat.

CRC Press, New York, NY, 1998.

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