The World Health Organization (WHO) Expert Committee on the Control of Schistosomiasis defined categories of schistosomiasis based on the number of eggs excreted.
Urinary Schistosomiasis
Number of Eggs Excreted in Urine
Category of Infection
Clinical Findings
1 – 49 per mL
light
hematuria frequent
>= 50 per mL
heavy
hematuria almost constant
Intestinal Schistosomiasis
Number of Eggs Excreted in Stool
Category of Infection
Clinical Findings
24 – 96 per gram stool
light
hepatomegaly rare
120 – 792 per gram stool
moderate
hepatomegaly frequent
>= 816 per gram stool
heavy
hepatomegaly almost constant
where:
• The number of eggs in the stool is based on the Kato-Katz slide which processes 41.7 mg of feces (which is 1/24th of a gram). This uses 1 - 4, 5 – 33, and >= 34 eggs to separate the light, moderate and heavy categories.
• A single Kato-Katz examination does not allow separation of light and moderate patient groups. If the data is examined as a Poisson distribution, then the difference between 1 and 5 eggs in the Kato-Katz slide is not statistically significant.
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