Faecal Sampling

Question 1

Why do we collect faecal samples?

Answer 1

Provide info on GI tract and how well it’s functioning - can aid diagnoses of parasites in GI tract

Question 2

What are the 2 ways in which faeces can be collected and what are the advantages/disadvantages?

Answer 2

1. Direct from Ground
   - has to be fresh!
   - has to be from correct pet!
   - Easy for owner to do
2. Direct from Rectum
   - PPE and lube (to avoid skin flora in sample)

Question 3

How should faecal samples be stored?

Answer 3

Ideally, should be examined within 2 hours or stored in the fridge with as little air in the sample as possible (or can add double the volume of formal saline).
Ideally 5g of sample should be collected.
If anaerobic examination required then as much faeces as possible should be put in tube to minimise air and prevent the reduction of viable anaerobic bacteria in the sample.

Question 4

What are the normal contents of carnivore faeces?

Answer 4

Water
Small amounts of undigested food
Pancreatic secretions - enzymes
Bile Products
Small amounts of mucus
Bacteria
Small numbers of Epithelial cells
Small amounts of blood or hair from prey

Question 5

What are we looking for in a faecal sample?

Answer 5

Signs of undigested food or ingested materials
Parasites
Blood

Question 6

What are the 3 ways faeces can be examined?

Answer 6

Gross examination (observation)
Microscopy (Smears)
Concentration Methods (Flotations, sediment)

Question 7

What do the colour variations in faeces mean?

Answer 7

Brown - normal
Black - melaena (bleeding from SI)
Red - Haematochezia ( bleeding from LI)
Yellow - malabsorption of nutrients / liver disease
White - eaten too many bones or too fatty a diet

Question 8

What does a rancid smell of faeces indicate?

Answer 8

Malabsorption of nutrients

Question 9

What does fatty or mucoid faeces indicate?

Answer 9

Exocrine Pancreatic Insufficiency or Colitis

Question 10

What can a direct smear be used to look for?

Answer 10

Worm eggs
Partially digested food (presence would suggest EPI)
Protozoan oocysts

Question 11

Describe the method for a direct smear

Answer 11

1. Place a drop of saline in the centre of a microscope slide
   Add an equal volume of faeces
   Add a stain
   Mix well, make a thin smear and add a cover slip
   Low power to look for worm eggs and high power for protozoa

Question 12

What are the stains you can use for a faecal smear?

Answer 12

Lugols iodine - stains starch blue/black
Methylene Blue - shows undigested meat fibres
Sudan IV - shows fat globules red

Question 13

What are the adv and disadv of a direct smear?

Answer 13

Cheap and Easy
But Qualitative (I.e. it only detects heavy infestations)

Question 14

What does the floatation method depend on?

Answer 14

The weight of certain debris and the use of liquids with different SGs

Question 15

What is the specific gravity of
water
parasite eggs
salt/sugar solutions?

Answer 15

1. 000
2. 100-1.200
3. 200-1.350

Question 16

What happens to faeces in a salt/sugar solution?

Answer 16

Heavy debris sinks to the bottoms - light eggs rise to the surface

Question 17

What is the most common faecal flotation? what do you have to be careful of when using it?

Answer 17

Sodium nitrate

- it will form crystals and distort the eggs if left to stand for more than 20 minutes

Question 18

What are the 3 types of flotation tests?

Answer 18

1. Standard
   - Test tube used where faeces are mixed with flotation solution. Cover slip left on top. Parasitic eggs float up and stick to slide. Then examine.
2. Centrifuge
   - quicker and more effective
   - spin tubes at 1000-1500rpm for 3-5 minutes
3. Commercial Kits
   - come with tubes, sieve and solution
   - expensive!

Question 19

Describe the standard flotation method

Answer 19

Mix faeces with water (3g faeces + 50ml)
Put mixture through a sieve
Put the filtrate in a test tube and leave for 5 mins
Pour off supernatant and add flotation solution
Fill the test tube to top and add meniscus
Place a cover slip over the top and leave for 15-20 mins
Lift cover slip off vertically and examine under microscope at 25x

Question 20

What does a sediment test do?

Answer 20

It allows the parasitic eggs and oocysts to sink to the bottom of a liquid (usually water)

Question 21

When is a sediment test used?

Answer 21

Used if suspected infective eggs are too heavy to float for a flotation test

Question 22

Describe the method for a sediment test

Answer 22

Mix 2g faeces with tap water and strain
Half fill a centrifuge tube with filtrate
Spin at 1500rpm for 5 minutes
Pour off the supernatant
Put some of the sediment onto a slide with a pipette and put cover slip on
Lugols iodine can be mixed with the sediment but can be difficult to see the eggs in all the debris

Question 23

What is the outcome of the Modified McMaster Technique?

Answer 23

Determines the number of eggs per gram of faeces

Quantitative assessment

Question 24

What are the disadvantages of the Modified McMaster Technique?

Answer 24

Clinical signs are not caused by the eggs

Egg numbers are different across species and may be sporadic

Question 25

Describe the method for the Modified McMaster Technique

Answer 25

Add 3g of faeces to tap water
Sieve and collect filtrate
Pour filtrate into 15ml centrifuge tube
Centrifuge at 1500rpm for 4 mins
Pour off liquid at top
Add sodium chloride to the tube and mix 
Fill McMasters chambers
Put under the microscope
Count the number of eggs in each grid and add together 
Multiply this number by 50. This gives you the number of eggs per gram of faeces.

Question 26

When would you see occult blood?

Answer 26

In chronic bleeding form ulcers, neoplasia, parasites

Question 27

Define malaena

Answer 27

Changed blood in faeces

Question 28

Define Haematocheza

Answer 28

Fresh blood in faeces

Question 29

How do we determine if occult blood is present?

Answer 29

Chemical reaction

• place animal on meat free diet for 3 days prior
• Use reagent (either ortholudine or benzidine)
• both react with hb peroxidase with occult blood in the faeces to produce a colour change

Question 30

What other faecal tests are there?

Answer 30

Faecal trypsin
Undigested fat - use Sudan IV stain
Bacterial Culture
Baermann Technique - add faeces to warm water to encourage larval parasites to move and sink to bottom.