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

DIRECT EXAMINATION

Macroscopic Examination

• Macroscopic examination of faeces is made for consistency, colour, present of blood or mucus, presence of adult or larval parasites, spontaneously discharged tapeworm segments, immature amphistomes and nematodes (roundworms, pinworms, Trichuris etc.).
• They can be recognized by direct macroscopic inspection of the faeces, by decantation of faeces in water in a glass tray or by pouring the faeces mixed with tap water through a sieve (mesh: 0.3mm), which will retain the worms.
• These are then transferred into saline in a petridish and can be observed against a dark background by the naked eye or by using a magnifying lens.

Microscopic examination

• Unstained smear

  • Procedure
    • It is possible to demonstrate the eggs or larvae of helminths, by the examination of a thin smear of emulsified faeces.
    • Place several drops of saline on a slide with an equal volume of feces  
    • Mix the solution and feces together with a wooden applicator until the solution is homogenous
    • Smear the solution over the slide into a thin film
    • Place a cover slip over the smear
    • Examine the area of the slide under cover slip with the compound microscope.
    • The slide is investigated using a magnification of 10x and 40x.
  • Merits
    • This method is quick.
    • Minimal equipment is needed.
  • Demerits
  • It is effective only when the concentration of parasite stages is high.
  • It is frequently difficult to identify them since they are partially covered by debris.
  • Quantitative results cannot be obtained.

• Stained smear method

• Iodine violet mount
• Lactophenol cotton blue method
• Parasites found with the direct smear method:
  • Coccidia and helminth eggs (only when high numbers are present); Cestodes and trematode eggs (mainly in birds).

• For intestinal schistomiasis / portal schistosomiasis

  • Collect the dung with mucus.
  • Place 2-3 drops of 4% KOH or 4% NaOH solution on a slide.
  • Take a little quantity of mucoid dung and mix it with the alkaline solution on the slide.
  • Keep the slide for some time so as to allow mucolysis to take place.
  • Spread the suspension evenly.
  • Place a coverslip and examine under low power objective of the microscope.

Result

• Egg of Schistosoma spindale will appear as spindle shaped / Napolean hat shaped with a terminal spine at one end.
• Egg of Schistosoma indicum appear as elliptical with a terminal spine at one end .

Note

• Be sure the density of the mount is correct. You should be able to read small print through it (but not too clearly). If it is too thick or too thin, observation of the elements in the mount may be difficult.