Knott’s Concentration Technique

Knott’s Method is a concentration technique used for the detection and identification of microfilariae in blood, especially when parasite levels are low. It is one of the most sensitive methods to detect Wuchereria bancrofti and Brugia malayi.

🔬 Knott’s Concentration Technique — Overview

Feature	Description
Purpose	To concentrate and detect microfilariae in peripheral blood
Type	Quantitative and diagnostic method
Sensitivity	Higher than thick smear or buffy coat smear
Samples used	1 mL venous blood, preferably collected at night (nocturnal periodicity)
Stain used	Giemsa or Hematoxylin

🧪 Procedure (Modified Knott’s Method)

Step	Action
1	Mix 1 mL of blood with 9 mL of 2% formalin in a centrifuge tube
2	Mix gently and allow to stand for 10 minutes for red cell lysis
3	Centrifuge at 1500 rpm for 5–10 minutes
4	Discard the supernatant carefully
5	Prepare a smear from the sediment on a glass slide
6	Stain with Giemsa stain (or methylene blue or hematoxylin)
7	Examine under low and high power microscopy

🔍 Advantages

Benefit	Notes
High sensitivity	Detects even low-density microfilaremia
Morphological clarity	Preserves morphology of microfilariae for species identification
Inexpensive	Uses simple lab reagents

⚠️ Limitations

Limitation	Details
Requires centrifuge	Not ideal for resource-limited field settings
Risk of formalin exposure	Requires PPE and safe disposal
Not suitable for sheathed parasites without staining	Identification can be difficult without proper stain

🧬 Species Differentiation

Knott’s method allows visualisation of:

Species	Morphology Notes
Wuchereria bancrofti	Sheathed, nuclei do not reach tail tip
Brugia malayi	Sheathed, two terminal nuclei at tail tip
Loa loa	Sheathed, continuous nuclei to tail tip
Mansonella spp.	Unsheathed, nuclei extend to tail tip (species-dependent)

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