ANSWERS

1. Why should a faecal sample be stored with care, and not for an undue length of time?
   
   • Bacteria will rapidly multiply in an old sample and therefore the results of any bacteriological tests may not be truly representative.
   • Old faecal samples may ferment causing the lid to blow off.
2. What is the most suitable type of receptacle for the collection of a faecal sample?
   A 30ml plain universal container with a tight screw top cap. Many commercial types incorporate a small spade into the lid for ease of use.
3. Why should a faecal sample container ideally be filled to the top?
   So that there is less air inside. Air is necessary for the replication of aerobic bacteria; see Q1.
4. What points of interest should be noted on a visual examination of faecal matter?
   
   • Colour.
   • Odour.
   • Consistency.
   • Presence of mucous.
   • Presence of blood.
   • Presence of undigested material.
   • Any foreign material such as hair or bone fragments.
   • Evidence of parasitic infestation such as worms or their ova.
5. What is the most probable cause of haematochezia (frank blood) in faeces?
   Colitis; the lining of the colon becomes inflamed (usually as a result of bacterial infection or dietary indiscretion) and fresh blood is visible in the sample. 24 Hours starvation followed by a bland diet will usually resolve the problem.
6. What is meant by occult blood?
   Blood present in the faeces in such a small concentration that it cannot be seen by the naked eye. It is usually evidence of insidious chronic bleeding from ulcers, neoplastic lesions or parasitic infestation. Biochemical detection is required to confirm the presence of occult blood (orthotoluidine or benzidine reacts with haemoglobin peroxidase in faeces to yield a visually detectable colour change).
7. Why must an animal be fed a meat-free diet for 3 days prior to the collection of a faecal sample for occult blood testing?
   The reagents used for the biochemical detection of occult blood are so sensitive that they will react with any dietary haemoglobin.
8. What is the name of the brown-orange bile pigment found in faeces?
   Stercobilin.
9. What is melaena?
   Blood originating from the small intestine giving faeces a dark colour; this is usually serious and evidence of dramatic bleeding.
10. What is the name of the counting chamber used to assess the quantity of worm eggs in faeces?
    The McMaster slide.
11. Why are faecal flotation tests such as the McMaster technique and Ovassay method useless when looking for tapeworm ova?
    Both tests rely on a saturated salt solution in which to suspend the faeces. Whilst roundworm eggs float and are therefore held in suspension, tapeworm ova sink to the bottom and are therefore not evident.
12. You are asked to examine some faecal smears; what stains would you use and why?
    
    • Lugol's iodine = stains starch granules blue-black (amylase deficiency).
    • New methylene blue = stains undigested meat fibres (trypsin deficiency).
    • Sudan III = stains faecal fat orange (maldigestion).