Abstract:
Background: Freshwater snails serve as intermediate hosts for different digenetic trematode
species that cause snail borne diseases of humans and animals. Different environmental factors
and human activities affect the abundance and infection rate of the snails. Environmental
conditions in Africa favor the growth of snail and trematode which has the potential to become a
public health problem in many countries. In addition to environmental conditions, there are other
different factors that cause a high prevalence of schistosomiasis, these are water resources
development projects, irrigation, fishing, population increase, and migration. These conditions
favor infection of freshwater snail and increase the risk of schistosomiasis infection.
Objective: the main objective is to determine prevalence of cercarial infection in Biomphalaria
snails and S. mansoni infection among fishermen in Lake Hawassa and Tikur Wuha River in 2020.
Methods and materials: The snails were collected from 26 sampling sites and examined for
cercarial infection using natural shedding method. The cercariae were identified morphologically.
In the surveyed sites the data on environmental factors, human disturbance, demographic and
behavioral factors were collected. Stool samples from fishermen were examined for S. mansoni
infection. To determine factors influencing the prevalence of snail infection PCA was used. Chi-
square was used to assess the association between S. mansoni infection and the risk factors.
Results: The study indicate that only Biomphalaria sudanica snail species were infected with
cercaria. Five different types of cercaria were recorded with a total prevalence of 12.03%. Of which
BAD (human schistosome) cercariae were the dominant accounting 37.5 % of all recorded cercarial
type. The prevalence of cercarial infection in snails positively influenced by BOD 5 , turbidity, total
suspended solids, human activities, and habitat condition. The total prevalence of S. mansoni
infection among fishermen was 14.7% and significantly associated with frequency of swimming
and educational status.
Conclusion and Recommendations: The prevalence of intestinal schistosomiasis was 14.7%
among the fishermen which transmitted by the vector Biomphalaria intermediate host snails. The
prevalence of cercarial infection in snails was high in this area which results high risk for the
transmission of schistosomiasis. Therefore, an intervention programs should be focused on the
snail control, provision of adequate sanitation, and health education to control the transmission of
schistosomiasis.
