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

SEDIMENTATION TECHNIQUE

Procedure

• Place a lump of faeces (1/2-1 tsp / 5-10 g/ 5-10 faecal pellets (of sheep or goats) in a cup or glass container.
• Add enough tap water and mix thoroughly with a spatula / glass rod until all the faecal material is broken down.
• The mixture is poured through a wire mesh sieve to remove coarse large lumps. Common tea strainer will do. The strained fluid is collected in a bowl. The sieve is rinsed with water and the debris left on the sieve is discarded.
• Transfer the suspension to centrifuge tubes and centrifuge at 2000 rpm for 2 min.
• Discard the supernatant.
• Mix the sediment well and take a small quantity of it and mix it with a drop of water on a clean slide.
• Apply a cover slip and examine under low power objective of the microscope.
• Thickness of the smear should be such that if the slide is placed on a newspaper, you should be able to read the fine print through the smear.

Note

• Select a fully representative sample of the stool for concentration.
• Prepare well-mixed suspensions of faeces and water or saline.
• Use the appropriate quantities of materials.
• Use the correct centrifuge speed and time.
• Prepare and examine mounts carefully as described for direct wet mounts.
• Do not discard the tube containing the concentrated material until you have completed your examination. You may need to make another mount.

Parasite stages detected with the sedimentation method

• Eggs of trematodes
• Larvae of lung worms
• Eimeria oocysts

Merits

• This is one technique by which the trematode eggs can be recovered. Operculated eggs like that of Diphyllobothrium latum also will be sedimented.

Demerits

• Usually the lighter eggs of nematodes and oocysts of protozoa are missed while employing this technique. Hence it is not considered by many people as suitable for these types of parasites.
• The presence of debris which may pose a problem whie doing examination.