Authors

S Jones¹; P Makaula²; A Juhasz¹; L Cunningham¹; J Archer¹; J Musaya²; S Kayuni¹; JR Stothard¹;  ¹ Liverpool School of Tropical Medicine, UK;  ² Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Malawi

Discussion

Commencing in October 2021, quarterly malacological surveys have been carried out at 12 locations in Mangochi, Chikwawa and Nsanje Districts in Malawi. These studies have been aimed at determining the spatial distributions of intermediate snail hosts of parasites of medical and veterinary importance. In March 2023 the lymnaeid snail Pseudosuccinea columella was first noted in Nsanje District and then again identified in Mangochi and Chikwawa Districts in June 2023, as well as an additional site in Nsanje. Of note one of the sites in Mangochi where the snail was found is directly connected to Lake Malawi, expanding the list of potential intermediate hosts of parasites in the lake. Specimens of P. columella were initially identified through the snail's characteristic shell micro-sculpture, differentiating it from the more common Radix natalensis. Molecular typing was then performed on snails transported back to the Liverpool School of Tropical Medicine and analysis of the mitochondrial ribosomal 16S region confirmed that the samples were P. columella. While P. columella is a well-known intermediate host for human and animal fascioliasis, through both Fasciola hepatica and Fasciola gigantica, no evidence of infection was found through either observed cercarial shedding or molecular xenomonitoring. However, the presence of this snail in Malawi, especially in the lower Shire valley and Lake Malawi raises concerns for altered local transmission for human and animal fascioliasis.