The study area is Okigwe. It is the zonal capital of Okigwe district in Imo State of Nigeria. The district is made up of six Local Government Areas namely: Isiala Mbano, Ihitte Uboma, Ehime Mbano, Onuimo, Obowo and Okigwe. The study area lies between latitude 5°30-5°57N and longitude 7°04-7°26 E (covering a land area of about 1,824 km². (www.maplandia.com).

The main occupation here is peasant farming and petty trading, The major source of protein for most individuals is snail consumption. Some individuals also trade on snails as sources of income for sustenance. Freshwater canals are common sources of water for several domestic activities , while the source of drinking water is from bore holes which are strategically located for commercial purposes. The residents travel few kilometers to purchase the drinking water.

Snail collection was carried out from May-July 2021. The study site was visited weekly for snail collection using a long plastic spoon and hand picking wearing a hand glove. The sites where the snails were collected were mainly in places where there are obvious constant human activities like school compounds. The freshwater snails collected were transferred to a labeled plastic container that was covered with a net for ventilation and air passage.

The collected snails were taken to the Department of Animal and Environmental Biology laboratory, Abia State University where the snails were sorted and identified by specie level using morphological characteristics standard key as described by Gillei (1986). The identified snails were counted and recorded.

The collected snails were put in petri dishes with a little quantity of water in the dishes and thereafter, placed under the sun. The petri dishes were monitored for cercariae shedding at the intervals of 30 minutes using a dissecting microscope and hand lens. The number of snails that shed was recorded and those unable to shed also recorded. Water quality index was determined using the methods described by Association of Official Analytical Chemistry (AOAC, 2005).

The fact that the snails collected were more in May and June when the rains are not yet heavy than the ones collected in July when rainfalls are heavy, shows that snails breed less during heavy rains than other periods. The result obtained from the study showed the abundance and diversity of freshwater snail intermediate hosts in the water canals studied. This abundance and diversity of freshwater snail hosts are of public health importance because of the risks to human infections. This finding corroborates with that of 118 that the presence of freshwater snails is of public health importance because of the indication for parasitic transmission.

The high proportion of cercariae shed in both Lymneae and Bulinus genera reflect the extent to which consumers of these snail species and those with regular contacts with the freshwater canals including school children are exposed to infections. The findings that individuals living in this vicinity use water from the canals for domestic activities means that they are likely to have regular contacts with the freshwater from the canals and therefore, human and animal excreta may be common in the freshwater where the snails grow. This finding agrees with those of 192033 in which they observed that freshwater body is usually polluted with human and animal excreta and that snails that grow in freshwater body polluted with human and animal excreta produce some organic matters that increase the concentration of detritus and the proliferation of algae which form the diets for planorbid and prosobranch snails.

The fact that some of the infected freshwater snails studied were of Bullins specie which serves as intermediate host to highly infective larval trematode of the genus Schistosoma shows that Schistosomiasis infection may be common in the study area especially among school children who were seen swimming in the canals near their school premises as well as picking snails for food. This regular human contacts with the canals presupposes the extent to which the surface water must have been contaminated by excreta and others.

The finding that majority of the freshwater snails that were infected were of the Lymmeae specie which according to studies by 28 is the chief intermediate host of Fasciola which predisposes human and animals to liver disease (fascioliasis), shows that some individuals resident in this area may be infected with fascioliasis.

Realizing the fact that snail is the main source of protein and avenue for generating revenue for sustenance among some residents in the area of study, presupposes that a significant proportion of the residents may have continuous contacts with the definitive host which would influence the occurrence of disease conditions like fascioliasis, schistosomiasis and others. Other human activities near the canal such as farming, bathing, swimming, washing of clothes, cassava and vehicles that were observed during the study, may be what contributed to the poor environmental conditions noted around the freshwater canals. These numerous human activities suggest constant contacts with parasites which occur on aquatic plants that serve as foods and shelter to freshwater snails thereby, increase their number and diversity. Also the fact that there is increase in the number and diversity of the freshwater snails make them available even on semidried soils where they are easily picked by individuals. One striking observation in the study is that a good number of individuals picking these snails move barefooted, thereby add to the predisposing factors to schistosoma and Fasciola infections as also pointed out in the researches done by 610.

The finding that dissolved oxygen (DO), Biological oxygen demand (BOD) and P^H significantly influenced snail distribution in the area shows that the presence of snails increased the biomass of filamentous green algae and decrease the biomass of periphyton thereby reducing the DO of the water which is needed by aquatic organisms for existence. This finding agrees with that of 1125.

This shows that the more the presence of snails, the more the biomass of periphyton is reduced.