Observations on the techniques used in the qualitative and quantitative diagnosis of schistosomiasis

For many years, the Visser filter has been used in various laboratories in South Africa for the qualitative and quantitative diagnosis of human schistosomiasis. In the present study, the effectiveness of the Visser filter was compared with those of the urinalysis method for urine (involving the use of small transparent filters in Millipore filter holders attached to 10-ml syringes) and the Kato-Katz thick smear method for faeces. The Visser filter was the most sensitive in detecting ova in human excreta. Furthermore, there was little agreement between the egg counts obtained using the Visser filter and those obtained with the other two techniques. The Visser filter owes its effectiveness and superior sensitivity to the fact that, compared with the other two techniques, larger quantities of urine (total bladder contents) and stool (up to 5 g) can be easily processed.