Abstract
The human disease schistosomiasis (or bilharzia) is caused by the helminth blood fluke parasite Schistosoma mansoni, which requires an intermediate host, the freshwater gastropod snail Biomphalaria glabrata (the most common intermediate host). The free-swimming parasite miracidia utilise an excellent chemosensory sense to detect and locate an appropriate host. This study investigated the biomolecules released by the snail that stimulate changes in the behaviour of the aquatic S. mansoni miracidia. To achieve this, we have performed an integrated analysis of the snail-conditioned water, through chromatography and bioassay-guided behaviour observations, followed by mass spectrometry. A single fraction containing multiple putative peptides could stimulate extreme swimming behaviour modifications (e.g. velocity, angular variation) similar to those observed in response to crude snail mucus. One peptide (P12;—R-DITSGLDPEVADD-KR—) could replicate the stimulation of miracidia behaviour changes. P12 is derived from a larger precursor protein with a signal peptide and multiple dibasic cleavage sites, which is synthesised in various tissues of the snail, including the central nervous system and foot. P12 consists of an alpha helix secondary structure as indicated by circular dichroism spectroscopy. This information will be helpful for the development of approaches to manipulate this parasites life cycle, and opens up new avenues for exploring other parasitic diseases which have an aquatic phase using methods detailed in this investigation.
Highlights
Worldwide, an estimated 200 million people are infected and over 800 million people are at risk of infection of Schistosomiasis [1,2,3], while over 200,000 people yearly will die from schistosomiasis-related illness [4]
Our study identifies the first kairomone released by the freshwater gastropod snail Biomphalaria glabrata, an intermediate host for the helminth blood fluke parasite Schistosoma mansoni
This is a key aspect of the S. mansoni life-cycle that leads to human infection, causing the disease schistosomiasis, which is considered the most devastating human helminth infection in terms of global morbidity and mortality
Summary
An estimated 200 million people are infected and over 800 million people are at risk of infection of Schistosomiasis [1,2,3], while over 200,000 people yearly will die from schistosomiasis-related illness [4]. This disease has a high morbidity rate, being responsible for the loss of up to 4.5 million disability adjusted life years annually[5], providing strong humanitarian and economic incentive to conduct research on various aspects of the epidemiology and ecology of the disease [6, 7]. Long-term solutions could be forthcoming through more in-depth investigation of the first stage, where schistosome miracidia locate and infect their snail hosts after egg hatching
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