Fig. 2

Density of snails (number of snails per standard search), infected snails, and mean water and air temperature, by month, from January 2004 to December 2005, in the East Nile locality, Khartoum, Sudan. a Biomphalaria pfeifferi infected with any trematodes, (b), Bulinus truncatus infected with xiphidiocercariae, (c) and Melanoides tuberculata infected with parapleurolophocercous cercariae