What is the purpose of the Kato-Katz technique in parasitology, and what limitation does it have?

• A. To quantify helminth eggs in stool
• B. To quantify helminth eggs in stool and estimate infection intensity; limited sensitivity in low-intensity infections and when sample is not fresh
• C. To detect parasite DNA
• D. To culture parasites

Answer: (B)

Kato-Katz is a quantitative stool technique used to measure how many helminth eggs are being shed, which lets us estimate infection intensity by expressing the count as eggs per gram of stool. By applying a standardized amount of stool to a slide and examining it under a microscope, a technician can convert egg numbers into a measure of parasite burden, a useful metric for assessing disease impact and monitoring program effectiveness. The method is especially employed for schistosomiasis and intestinal nematodes because it provides a simple, field-friendly way to get comparable counts across individuals and populations.

The key limitation is sensitivity. In people with light infections, egg counts can be very low, so a single preparation may miss eggs and underestimate true infection prevalence and intensity. Freshness of the sample matters as well—if the stool isn’t processed promptly, eggs can degrade or clear, further reducing detectability. Because of these factors, Kato-Katz may underdiagnose low-intensity infections or require multiple samples to improve accuracy. It doesn’t detect parasite DNA or enable culture; it solely relies on visible eggs on microscopy.