VLD 411: Veterinary Clinical Biochemistry and Laboratory Diagnosis - I (0+1)

DUNG / FAECAL SAMPLE

Collection

• Faeces intended for parasitological examination should be collected from the rectum unless the animal is observed in the act of defecation when the sample may be collected from the ground.
• With large animals, collection of faeces from the rectum can be accomplished by hand without difficulty.
• Smaller animals such as young lambs and dogs can usually be induced to defecate by inserting a moistened finger into the rectum and gently massaging with a rotary motion until the external sphincter relaxes.
• For dogs, in the event of non-availability of proper faecal sample, moist cotton swabs, introduced into the rectum and rotated well to collect the maximum possible faecal matter and dipped in saline in a test tube, are useful for examination of eggs.
• Samples should be collected from several animals in an affected herd, some of which should be collected from the most seriously affected animals and a few from the less seriously diseased animals in order to observe the contrast in the counts.
• Faecal samples collected from the ground in a field in which the animals have been running, are less useful for diagnostic purposes, but where rectal sample cannot be obtained, these should be examined. Such samples should be selected from the top of the most recently dropped faeces and several samples should be collected.
• The detection of parasitic stages in faeces of animals suffering from diarrhoea may be markedly impaired.
• The diagnosis of parasitism by microscopic techniques is more reliable when repeated examinations are made. For example, negative results are sometimes obtained from faecal examinations if the parasites are not mature enough to deposit eggs. This might also occur when they are enclosed in the tissue nodules such as Strongyles or Oesophagostomes.
• Tapeworm segment often leave the digestive tract without disintegrating and negative results may be obtained unless segments are detected.

Preservation

• Since eggs embryonate rapidly, the faeces should be stored in the refrigerator unless examination is carried out within a day.
• For samples that are to be sent through the post, the faeces are fixed and preserved in 10% formalin to minimize development and hatching.

Despatch

• Suitable containers for the dispatch of samples to the laboratory are:
  • 30 ml wide mouthed screw capped bottles of glass or preferably of plastic, which should be filled to the top if possible so as to exclude air as much as possible and diminish the rate of development and hatching of the eggs.