The identification of a schistosome species that is cycling through a Helisoma snail was an important discovery for FWS in 2018. This genus of snail is typically not considered when swimmer’s itch and schistosomes are being discussed. This summer we will collect and shed Helisoma snails to measure infection rates, along with assessing them for infection using CO1 barcoding for both the snail and any putative schistosome shed from it. We will also include additional species of bird in our shoreline bird surveys to attempt to conclusively identify the avian host of this schistosome. We hope to map the prevalence of this parasite in the lakes of Northern Michigan that we are studying.
FWS is investigating why, with annual and continued relocation of common mergansers from numerous lakes in Northern Michigan, T. stagnicolae remains the most prevalent schistosome, and possibly the most significant driver of swimmer’s itch. By collecting and analyzing water samples with qPCR, this project will provide data about the temporal shedding nuances of all avian schistosomes from early spring into late fall. We hope to be able to tell what role migrant birds are playing in swimmer’s itch infections.
Optimizing the merganser trap and relocate control protocol is important because it is rapidly growing in popularity across Northern Michigan. FWS is working to find relocation sites that are suitable for merganser survival, ecologically stable enough to accept these artificially introduced vertebrates, and lack the intermediate snail host species capable of transferring parasites from one location to another. We analyze water samples from each site using qPCR to tell which, if any, species of schistosome is cycling in the water at these sites so that we can make a proper recommendation about use of these sites to the DNR.
FWS began a pilot study on several lakes in NW Michigan in 2018 in which water samples were taken, DNA was extracted from all organisms in each sample and a specific gene marker (HF183) found in bacteria (Bacteroides) unique to humans was amplified and quantified. Building off of this work, FWS is now working to answer a variety of questions using testing for enteric bacteria through qPCR. Questions may include how a major rain event influences enteric bacteria levels, if the presence of Cladophera sp. indicates a higher level of enteric bacteria, and how enteric bacteria levels in 2019 compare to those in 2018.
Years of experience have shown that a 90% reduction in parasite load, as measured by snail infection rate, does not translate into uniform swimmer’s itch reduction around the lake. Hot spots, where swimmer’s itch infection rates persist at high levels, still exist and create frustration for riparians, raising doubts about the effectiveness of control efforts. Spring or fall migrant mergansers undoubtedly transmit larval parasites to snails while visiting the lake, potentially aiding in creation of these hot spot areas.
FWS offers several new, innovative ideas to combat isolated hot spot areas. Testing began in mid-August of 2016 and showed some positive results. These new ideas were further tested to prove their level of effectiveness in 2017 and showed very promising results. Fortunately, qPCR offers a fast and precise way to measure success, allowing for modifications to be made and tested almost immediately. If continued research in 2018 proves equally successful, lake associations and individual riparians will have another powerful tool to reduce the incidence of swimmer’s itch in troublesome areas.
FWS is working on several new lakes to determine the natural history of the parasite(s) causing swimmer’s itch.. We are also collecting data to determine the level of parasite infestation on the lakes in order to establish a baseline for future comparison. Data collection includes water sample analysis via qPCR, snail analysis, and bird surveys.
FWS is working with interns from Elk Rapids High School to answer a variety of questions about golden algae growth, the prevalence of all snail parasites on Torch Lake, and the best way to calculate snail densities in an area. The aim is to give students a chance to produce authentic research, while growing the greater understanding of the Torch Lake ecosystem.