Sensitive Material Shear Modulus:

127 CHAPTER FIVE

DISCUSSION

5.1 SNAIL ABUNDANCE, DISTRIBUTION AND SPECIES COMPOSITION

128 A total of 26 Bulinus spp (9 (34.62%) from Iyiegwu and 17 (65.38%) from Obutu lakes were identified which may be due to adequate availability of vegetation and decayed organic matter for feeding and constant human-water contact activities in the lake. B. globosus prefers cluttered areas and low water flow and occurs in habitats that were slightly polluted with faeces or decaying vegetation. Careless discharge of effluent, animal and domestic wastes may be another reason more Bulinus species were recorded at Obutu lake. More people were seen doing one programme or the other in and around the lake causing more contamination of the lake with body fluids which is very conducive for survival of the snails.

Pila spp collected was 1617; (1108 (68.52%) from Iyiegwu lake and 497 (30.74%) from Obutu lakes). More Pila spp was collected from Iyiegwu lake probably because people do not scout for the snail in and around the lake as they do not live very close to the lake. Pila also prefers man-made habitats but Bulinus prefers shallow water where it may occur on bare substrate but commonly among aquatic plants. Bulinus can cling to or settle to the bottom of the water and later come out to the surface which would be made easier by the nature of the lake. Preference for different environmental conditions such as abundant microflora, depth of water, and other physico-chemical factors and natural behavioural mode of adaptation may explain why the snail species showed marked differences in each locality.

In both lakes, Pila ovata abundance was significantly higher than Bulinus globosus. This is in agreement with the work of Hug et al., (2000) who observed that Pila globosa was found more in Beel Chanda. He noted that an environment rich in Pistia stratiotes and other filamenteous algae always have high density of Pila species. This may be attributed to the fact that Pila species adapted more to the conditions or factors on the lake. The distribution of Bulinus globosus is patchy may be due to the fact that some freshwater snails are important food source for many fish, turtles and other species of wildlife. Johnson et al., (2010) reported that predators like Cyclops often consumed cercariae and this could be the reason Schistosome cercariae were not observed during the cercariae shedding process. The availability of Bulinus in the study area is an indication of imminent risk of urogenital schistosomiasis transmission in the area since the human water contact activities was observed in higher capacity.

Bulinus was collected from December to May coinciding with the period of dry season and early rains. It occurred at low density throughout the year in the lakes, but they showed a density-peak during the dry season. Bulinus thrive more during the dry season when there is no influx of rain when they can not be flushed out and this leads to frequency of activities in the lake due to inadequate water in the study areas. It was recorded that the population

129 density of Bulinus truncatus occurring in South east Ghana fluctuated markedly from season to season and greatest at the beginning of the dry season.

Pila ovata was collected more during the wet months (May-November) while Bulinus globosus was collected more during the dry months (January-April) in Iyiegwu lake. This is in consonance with the work of Greveldin (2004) who observed a lack of Bulinus spp during the rainy season.

In Obutu lake, almost the same observations were made where more Pila was collected during the rains (June-October) while Bulinus species was collected during the dry season of the year (December-March). This coincides with the work of Ezeugwu and Mafe, (1998) where they observed seasonal variations of snail species in two aquatic habitats. Pila ovata, they observed were more abundant during the wet season while Bulinus globosus decreased with change in season to wet months. The abundance of Bulinus during the dry season may be due to the fact that it coincides with the period when the aquatic habitats become stable in terms of water level and velocity. This also agrees with the report that Bulinus snail population drops during the heavy rains and picks up at the onset of dry season (Baalawy, 1972). Bulinus was not found during the rainy season but Akogun and Okon (1993) observed a fall in abundance of Bulinus during the dry season but picked up in May, the onset of rains with a peak between July and October.

Snails were collected from different parts of the lakes where there were frequent man-water contact points. Some were scooped from the floor towards the shallow edges of the lakes while some were picked on aquatic vegetation and trailing vegetations by the banks of the lakes. Most freshwater snails thrive in shallow water and also live in vegetations that serve them for shelter and feeding, they also stay around banks of water bodies for easy infestation to their hosts. Aquatic snail hosts of schistosomes occur in shallow water near shores of lakes, ponds, marshes and irrigation channels. They live on water plants and mud that is rich in decaying organic matter. They can also be found on rocks, stones or concrete covered with algae or on various types of debris.

Freshwater snails were collected from water contact points, water crossing routes and on underneath of floating vegetation. This makes it easier for the snail to infect human host through penetration and also for protection and feeding. Freshwater snails occur exclusively in low-depth marshes with plenty of floating, emergent, and submerged vegetation. Some live on aquatic plants or on rotten leaves found in lentic environments, or in water bodies with slow water flow and low pollution degree (Appleton et al., 2009). Amawulu et al.,

130 (2008) observed that freshwater snail intermediate hosts of schistosomiasis are found in excavations, gutter/drains, water pools near and under vegetation and streams.

5.2 ECOLOGICAL/PREDISPOSING FACTORS