Malacological and Parasitological Surveys on Ethiopian Rift Valley Lakes: Implications for Control and Elimination of Snail-Borne Diseases.

Beekam Kebede Olkeba,Seid Tiku Mereta,Gemechu Debesa,Argaw Ambelu,Mahmud Ahmednur,Peter L M Goethals,Pieter Boets,Wolyu Korma,Belayhun Mandefro

doi:10.3390/ijerph19010142

Abstract

Schistosomiasis is one of the snail-borne diseases responsible for the second-highest burden of diseases among neglected tropical diseases. The use of mass drug administration to the populations most at risk is a backbone of the strategy to prevent and control schistosomiasis transmission. However, it offers no protection against re-infection, and humans are often re-exposed when they return to water bodies where snails release cercariae. Surveys on cercarial infection in snails could provide better insights on human disease risk. Hence, in this study, we investigated cercarial infection in snails and also determined the epidemiology of Schistosoma mansoni among fishermen at Ethiopian Rift Valley lakes. Freshwater snails were collected from the shorelines of Ethiopian Rift Valley lakes for examination of cercarial infection during 2020. Environmental data on water quality variables and physical characteristics of snail habitats were collected. Stool samples were collected from fishermen and the Kato-Katz technique was applied for the quantification of Schistosoma mansoni eggs. A malacological survey indicated that six morphologically distinguishable types of cercariae were found in snails. Infected snails with cercaria were more likely present in habitats with high five-day biological oxygen demand and low dissolved oxygen. The overall prevalence of Schistosoma mansoni infection among the fishermen at Ethiopian Rift Valley lakes was found to be 21.5%. This indicates that fishermen at Ethiopian Rift Valley lakes are one of the groups of people harboring schistosome cercariae which are potentially responsible for the transmission of schistosomiasis to lakeshore communities who have contact with lake water. Therefore, complementary medical treatment, public health interventions, environmental management and snail reduction are needed to control the transmission of schistosomiasis.

Highlights

Snail-borne diseases form an important share of parasitic diseases that pose risks to human health and cause major socioeconomic problems [1]
This study aimed to (i) investigate cercarial infection in freshwater snails and (ii) determine the epidemiology of S. mansoni infection among fishermen, an important group being at risk, at Ethiopian Rift Valley lakes and its associated risk factors
A total of 257 snails were collected from the total of 96 sampling sites on the shorelines of Ethiopian Rift Valley lakes, 78 snails were infected which accounted for an infection prevalence of 30.5%.Infected snails were encountered at 20 sampling sites out of the total number of 96 sampling sites (20.8%)

Summary

Introduction

Snail-borne diseases form an important share of parasitic diseases that pose risks to human health and cause major socioeconomic problems [1]. Schistosomiasis and fascioliasis are two of the most common snail-borne diseases worldwide which are widespread in many tropical and sub-tropical countries. The medical and economic burden of these diseases are often neglected which is why they are included in the list of the neglected tropical diseases.

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