Analyzing the Microbiome of Avian Schistosomiasis Vector Gyraulus Parvus

Schistosomiasis is a neglected tropical disease caused by flatworms called schistosomes. Two of the most prevalent species of schistosomes are transmitted by a specific family of freshwater snails. An animal’s microbiome, which consists of all the microbes on and inside it, influences and is influenced by the animal’s immune system. Schistosome infections have been shown to change the microbiome compositions of schistosomiasis vector snails. Additionally, differences in snails’ immune systems have been shown to prevent schistosome infections. Given these observed relationships, the microbiomes of vector snails are an important topic of investigation. While schistosomiasis is not found in the United States, certain local snails belonging to the same family transmit the parasites for avian schistosomiasis. This study aimed to explore the microbiome of a local avian schistosomiasis vector, Gyraulus parvus. The microbiomes of two related snail species, Menetus dilatatus and Physa acuta, were also compared with that of Gyraulus parvus. Snail collection locations were scouted by surveying snail species present at 17 sites. Of these sites, 2 locations, Lake Fairfax and Wood Glen Lake, had all 3 species present. Three points along each lake were then chosen for sampling. Snails were collected by repeatedly washing decaying vegetation in water and straining the resulting liquid through a mesh sieve. Once the snails were collected, they were placed in tubes of water and exposed to 6 hour intervals of artificial light to encourage parasite emergence. To identify infections, the water samples were centrifuged, and the resulting sediments were examined under a microscope. Snail tissue was then extracted and homogenized in a blender. DNA was extracted from each sample and sent out for 16S targeted sequencing. Once the sequencing is complete, the composition of the snails’ microbiomes will then be analyzed based on species and location.

Hello, my name is Lulu Singer! Currently, I am a senior at George Mason University, where I am majoring in biology. ● For my URSP summer project, I studied the microbiomes of Gyraulus parvus and two other local snails. ● An animal’s microbiome is made up of all the microbes that live on and inside its body. ● These native microbes have a huge impact on their host. For example, your microbiome influences your food preferences, mental health, and immune system. ● We can’t exactly see these microbes, so instead, we look at the bacterial DNA in an organism and identify the different taxa we find. ● I was interested in Gyraulus parvus because of its veterinary and clinical significance. These snails transmit several parasitic blood flukes, known as schistosomes, that cause avian schistosomiasis in birds and cercarial dermatitis, or swimmer’s itch, in humans. ● Additionally, they are related to vectors of human schistosomiasis, which I hope to study in the future. ● The first step in this project was to scout for locations with all three snails. ● Then, I collected the snails and tested water from each location. ● Back at the lab, I sorted the snails by species, and retained the Gyraulus parvus, Menetus dilatatus, and Physa acuta snails. Menetus dilatatus is in the same family as G. parvus, and Physa acuta is in a sister taxon. ● I then placed the snails in an illuminated cabinet to see if any of them were infected. ● Light exposure encourages the parasites to emerge into the water, which I could then examine with a microscope. ● Once I had checked the samples for any infections, I cleaned the snails and homogenized their tissue. ● I then extracted DNA from the homogenized tissue samples, and sent it out for 16S targeted sequencing services. ● The sequencing service identifies the different bacteria found in the samples, which we can then analyze. ● With this data, we can identify the most stable part of the microbiome, known as the core microbiome, for each species. These are the bacteria that were found in all samples, and accounted for a significant percentage of sequences. ● We can also compare the microbiomes of different species, and see how similar or different they are from each other. ● As I mentioned before, I was interested in Gyraulus parvus as a local snail of veterinary interest. However, I was also drawn to them because many species of schistosomes that cause schistosomiasis in humans are transmitted by snails in the same family. ● Schistosomiasis is a neglected tropical disease caused by schistosomes in the genus schistosoma, and transmitted by freshwater snails. ● This disease affects roughly 240 million people every year, but receives little attention because it affects vulnerable, low income populations. ● Currently, schistosomiasis prevention involves mass drug administration or controlling the snail vector populations. ● However, current snail control involves spraying toxic molluscicides that kill other aquatic life, and make the water temporarily undrinkable. ● Some snail vectors of schistosomiasis have shown resistance to schistosome infection. This resistance has been linked to variations in the snails’ immune systems. ● We know that a snail’s microbiome is linked to its immune health, and when snails are infected, their microbiome’s change drastically. ● Microbiomics may be the key to developing an environmentally friendly and cost effective way to interrupt transmission. ● This project was especially important to me because it is relevant to research I wish to pursue in the future. Primarily, I hope to study the interactions between the snail vector microbiome, its immune system, and the schistosome parasites. ● Furthering our understanding of these snails’ microbiomes could be the first step in a new approach to disease prevention and control.