As the parasitological techniques rely on egg excretion, they
cannot detect infection during prepatency, and they have poor
sensitivity in light infections, in old chronic infections, following
treatment, or when the bile duct is obstructed causing intermit-tent egg excretion. Repeated examinations are needed to improve
diagnostic sensitivity of faecal examination. Three consecutive
Kato-Katz thick smears were reported to be more sensitive than a
single examinationby FECT