Sedimentation in parasitological coproscopy.

A sedimentation technique is described, in which a fecal suspension is placed on top of an aqueous sucrose solution of specific gravity 1.015 g/cm3. Using 100 by 15 mm test tubes, duplicate gravity sedimentation experiments were made using homogenized fecal suspensions (single-columns) and fecal suspensions placed on top of clear columns (double-columns). Egg and cyst counts, and turbidity determinations were made in the sediments obtained after definite time intervals. Most Ascaris lumbricoides, Trichuris trichiura and Ancylostomidae eggs sedimented within 20 minutes in single-and between 30 and 60 minutes in double-columns. Giardia duodenalis cysts required longer periods to sediment in double-than in single-columns; after 180 minutes (the maximum period of observation), double-column sediments produced 60.0% of the counts of single-columns. Double-column sediments were consistently less turbid than single-column ones.