Which technique is used to analyse faeces for parasitic larvae?

• A. Hanging drop technique
• B. Baermann's test
• C. Kato-Katz smear
• D. Ziehl-Neelsen stain

Answer: (B)

To detect living nematode larvae in feces, you need a method that pulls those motile larvae out of the stool so they can be seen under a microscope. Baermann's test does exactly that. In this technique, a small amount of feces is placed on a porous support inside a funnel and submerged in warm water. The larvae are active and will move out of the fecal material into the surrounding liquid, sinking to the bottom where they can be collected and examined. This approach specifically targets larvae because their movement is what drives them to migrate into the water, making it more sensitive for recovering larvae such as Strongyloides stercoralis.

Other methods focus on different parasite stages or organisms. The hanging drop method is used for observing motility directly in a drop of sample but isn’t tailored to efficiently recover larvae from feces. The Kato-Katz smear is designed to quantify and visualize eggs in stool, not larvae. The Ziehl-Neelsen stain is an acid-fast stain used to identify certain organisms like specific coccidia or Mycobacteria, not larvae.