The snail vectors were more abundant in stagnant waters. Percentage occurrence of Bulinus globosus (Morelet) was 44.4% in ponds, 44.3% in borrow pits, and 37.5% in lakes, while the occurrence of Bulinus forskali (Ehr.) was 62.3% in borrow pits, 48.1% in ponds, and 40.6% in lakes. Snail reproduction occurred in all months of the year with peaks in June and November and troughs in February and September. Snail density was related to the bottom substratum: 81.9% on mud, 72.2% on concrete, 20.0% on sand and 7.6% on silt. Snail infection with Schistosoma was high between October and December. The medium-sized class was most infected.