T7: Laboratory Procedures

Question 1

Why are faecal tests peformed?

Answer 1

to help diagnose causes of diarrhoea and weight loss

Question 2

What should you record in a gross examination of faeces?

Answer 2

1. Consistency (hard, soft, liquid),
2. colour (eg red indicates bleeding, black indicates digested blood)
3. presence of fat, mucus
4. presence of obvious material such as bone, hair, grass, worms/worm eggs, foreign bodies (plastic bag, chewed toys, socks and other underwear etc)

Question 3

Describe how you would prepare wet prep faecal smear

Answer 3

1. Put a drop of saline onto slide
2. Add an equal amount of faeces
3. Add stains if required, eg Lugol’s iodine, methylene blue
4. Mix and make a thin smear, cover with coverslip
5. Examine under microscope in a systematic manner at 10´ for worm eggs, and 40´ for protozoan oocysts. Begin at one corner of the cover slip, move down, and then back up until the whole area has been examined.

Question 4

Describe how to perform a faecal flotation

Answer 4

1. Place faecal sample into fecalyser container
2. Add flotation medium to level indicated
3. Mix thoroughly
4. Push down filter
5. Fill container with more flotation medium to the brim
6. Place a cover slip over the fluid meniscus, leave for 10-20 minutes
7. Carefully remove cover slip and place it onto a slide
8. Examine slide under microscope systematically to examine entire area.

Question 5

Describe how you would make a bacterial smear

Answer 5

1. Direct smear from swab - roll the swab directly onto the middle of a clean slide
2. Direct smear from tissue sample or pus.
3. Fluid sample - use a sterile pipette to put a drop of the fluid onto the slide.
4. Agar plate colony - put a drop of sterile saline onto the slide, then pick up a colony with a flamed cooled wire loop, and mix it with the saline.

Question 6

How can you collect fluids for samples?

Answer 6

• Aspirated
• (sucked up using a syringe) from abscesses, body cavities, joints, the spinal canal, heart or bladder, and transferred to these containers.
• If you are passing the needle through another surface to aspirate the fluid these other surfaces must be sterile.

Question 7

Name the three shapes bactera may be?

Answer 7

• cylindrical rods (bacilli)
• spherical cocci
• spiral shaped (spirilla or spirochaetes)

Question 8

What colour are gram +ve bacteria?

Answer 8

blue-purple

Question 9

What colour are gram -ve bacteria?

Answer 9

pink-red

Question 10

Describe how you would prepare a microbial plate (agar)?

Answer 10

1. Take your aseptically collected sample and place a small amount onto the agar near the edge of the petri dish.
2. Flame a wire loop until red hot, then cool; touch it to the agar to check it is cool
3. With the wire loop, touch the area where the sample was applied, and streak out several lines to cover one-third of the plate
4. Flame the loop, then cool
5. Streak through the pattern to cover the next 3rd of the plate
6. Flame the loop, then cool
7. Streak through again to cover the next 3rd of the plate
8. Flame loop.
9. Cover petri dish with lid
10. Place into incubator upside down (stops water condensing onto the colonies and agar surface).

Question 11

What is a biopsy?

Answer 11

a sample of tissue taken from a living animal for diagnostic purposes.

Question 12

What is cytology?

Answer 12

study of structure, function and chemistry of cells

Question 13

What is histology?

Answer 13

study of the structure and function of microscopic anatomy of plants and animals

Question 14

For fixation of tissue, what ratio of formalin to tissue should there be?

Answer 14

For optimum fixation and sectioning use 10% formalin; 10:1 ratio; and a biopsy size 10mm cubed

Question 15

Describe how to perform a skin scraping

Answer 15

1. Use a clean scalpel blade and a clean microscope slide
2. Place a drop of paraffin oil onto the slide
3. Clean the affected skin area with 70% alcohol swab
4. Squeeze the area
5. Apply a drop of paraffin oil to the scalpel blade
6. Use the scalpel blade to scrape the top surface of the skin at the edge of the lesion until minor bleeding occurs
7. Wipe the blade onto the slide to transfer sample material.
8. Add 2 drops of 10 % potassium hydroxide wait 30-40 minutes (optional)
9. Put on a cover slip and examine under the microscope

Question 16

Why are skin scrapings performed?

Answer 16

used to look for mites and fungal spores

Question 17

What is fluroscein staining used for in the eye?

Answer 17

checking the eye to see if a foreign body or scratch or blow, has caused a corneal ulcer

Question 18

Why are post mortems performed?

Answer 18

• Determine cause of death
• Assess treatment
• Confirm or refute diagnosis
• Disease surveillance
• Insurance purposes
• Legal purposes in suspected notifiable and exotic disease cases
• Flock/herd health management

Question 19

What information do you need to obtain from a post-mortem?

Answer 19

• the time of death (a post-mortem more than 24 hours after death may not yield any useful information)
• any suspicious circumstances surrounding the death
• a complete history of the patient particularly if not a current patient or a referral
• where the animal was found, and on which side the body was lying may be helpful
• what the owners wish to do with the body -after the post-mortem is completed.

Question 20

List the equipment needed for a post-mortem

( you may need some or all)

Answer 20

• scalpel handle and blades
• scissors (sharp-ended, straight blunt-ended mayo scissors)
• forceps: rat tooth and plain tooth
• bone/rib cutters: short-handled and long-handled secateurs
• hacksaw: large or small depending on the size of the animal
• butcher’s boning and skinning knives
• sharpening equipment including a sharpening steel, wet stone or oil stone with sewing machine oil
• buckets, disinfectant, mop and broom
• surface disinfectant in a spray pack
• plastic ruler
• equipment for specimen collection
• steel spatula with a wide blade for searing the surface of organs
• Bunsen burner with matches (portable units are available for sterilising forceps and heating the spatula)
• a jar of 70% alcohol (to hold scissors, forceps, scalpel, etc. ) 70 ml sterile containers
• transwabs (for microbiology)
• blood tubes: plain and EDTA
• 10% buffered formalin
• overalls or coat
• disposable latex gloves or re-useable rubber dish-washing gloves
• protective goggles and masks if needed
• strong non-slip impervious boots (gum boots are ideal, especially for large animal post-mortems).