Cercarial Transmission Seasons of Schistosoma mansoni in the Nile Delta Area

摘要

The cercarial transmission seasons of Schistosoma mansoni in the Nile Delta area were determined by 3 methods: (1) monthly cercarial infection rates in Biomphalaria alexandrina, (2) monthly numbers of infected snails collected by means of a uniform sampling method, and (3) monthly cercarial output and monthly numbers of infected snails collected by means of a uniform sampling method. It was found that the third method is more logical and defines more precisely the transmission seasons of S. mansoni in the area. The paper also includes a discussion on the important factors that influence the timing of mollusciciding operations for the control of schistosomiasis in the Nile Delta area.