A kinetic study of egg production, fecal egg output, and the rate of proglottid shedding in Hymenolepis nana.

To estimate the rate of shedding of the proglottids during normal development of Hymenolepis nana in mice, 2 parameters, i.e., egg production and fecal egg output, have been determined. Changes in the number of eggs/proglottid along the length of the worm showed that, not only in vitro but also in vivo, a considerable number of eggs is discharged in situ while the proglottids are still attached to the worm. The in situ egg discharge, however, accounts only for a small fraction of the eggs appearing in the feces, and it can be neglected in the estimation of the shedding of proglottids. In H. nana the larva rotates 90 degrees in the egg during its development. This seems to occur in a short period, quite in concert within each proglottid. The transition point (the proglottid where 50% of the eggs have begun rotating) can be a useful landmark to estimate the rate of proglottid shedding. Egg numbers at the transition points approximate the genuine egg production, because in situ egg discharge mostly occurs only after the proglottids have passed the transition point. The 3 processes, i.e., the rotation of the larva in the egg, the in situ egg discharge, and the shedding of proglottids, usually occur in an orderly way. However, on day 20 of infection, just before the worms are lost (or destrobilated), shedding of proglottids seems to be inhibited, whereas the other processes are apparently normal.(ABSTRACT TRUNCATED AT 250 WORDS)