Role of Lymnaea luteola in spreading Schistosoma incognitum in an endemic area

The potential transmission role of Lymnaea luteola, the snail intermediate host of Schistosoma incognitum in an endemic area, was studied. Out of 3 99 1 L. luteola collected from Marhai, Suhagi and Gorakhpur areas of Jabalpur, 134 (3.35%) were positive for S. incognitum cercariae with marked seasonal variation. L. luteola were experimentally infected in an artificially prep ared tank with pig faeces (60 or 160 g) harbouring S. incognitum miracidia. The snails started shedding S, incognitum cercariae on day 28 or 38 day po st-infection (DPI). Cercarial shedding was the highest on 28 to 43 DPI with the highest infectivity of 26 to 35%. Subsequently, the snails discharging cercariae diminished to 5-10% with no shedding of cercariae was seen from 58th to 65th DPI reflecting heavy mortality of positive snails within a sho rt period. The field collected snails (39) were found to discharge S. incog nitum cercariae for 1-15 days (average 6 days) till their death. The daily cercarial output per snail varied from 6.6 to 326.6 (minimum) and 106.6-1 0 06.6 (maximum). The total number of S. incognitum cercariae shed by a singl e snail during its life time ranged from 73 to 4 929 depending on days of s urvival of the snail.