Poster
14

First report of Biomphalaria in Lake Malawi and emergence of intestinal schistosomiasis in Mangochi District, Malawi

Authors

M ALHARBI1; C Condemine1; R Christiansen1; E J Lacourse2; P Makaula1; S Kayuni1; J R Stothard1
1 Liverpool School of Tropical Medicine, UK;  2 Liverpool School of Tropical Medicine / UoL, UK

Discussion

First report of Biomphalaria in Lake Malawi and emergence of intestinal schistosomiasis in Mangochi District, Malawi Schistosomiasis is a waterborne neglected tropical disease of particular public health importance in Malawi. While urogenital schistosomiasis is endemic to Lake Malawi, local transmission of intestinal schistosomiasis is thought not to occur as Biomphalaria, the intermediate snail host of Schistosoma mansoni, has never been reported from the lake. However, during general malacological surveys undertaken in November 2017, we encountered Biomphalaria pfeifferi at 2 sampling sites along the Mangochi District shoreline. Snail species identity was confirmed by molecular DNA analysis of the mitochondrial cytochrome oxidase sub-unit 1 gene. Subsequently, in May 2018 with additional sites surveyed, B. pfeifferi was found at 9 further locations with its presence reconfirmed within the lake. School children (n≤175) from three primary schools located close to known B. pfeifferi sites were examined for intestinal schistosomiasis; the prevalence of S. mansoni infection was estimated by urine circulating cathodic antigen (CCA) dipsticks to be 46.7%, 25.0% and 9.1%, respectively. Upon faecal sampling and microscopy, several children had egg-patent S. mansoni infection. Our surveys provide an excellent example of how malacological surveillance can be used to target with more precision tailored parasitological surveys to pinpoint the focality of intestinal schistosomiasis. These observations are of local and national interest highlighting autochthonous transmission of S. mansoni and of international importance for updating travel medicine guidance and advice for the lake. Biomphalaria, the intermediate snail host of Schistosoma mansoni, has never been reported from the lake. However, during general malacological surveys undertaken in November 2017, we encountered Biomphalaria pfeifferi at 2 sampling sites along the Mangochi District shoreline. Snail species identity was confirmed by molecular DNA analysis of the mitochondrial cytochrome oxidase sub-unit 1 gene. Subsequently, in May 2018 with additional sites surveyed, B. pfeifferi was found at 9 further locations with its presence reconfirmed within the lake. School children (n≤175) from three primary schools located close to known B. pfeifferi sites were examined for intestinal schistosomiasis; the prevalence of S. mansoni infection was estimated by urine circulating cathodic antigen (CCA) dipsticks to be 46.7%, 25.0% and 9.1%, respectively. Upon faecal sampling and microscopy, several children had egg-patent S. mansoni infectio

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