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Sckrabulis JP, Messner ML, Stanny J, McWhinnie RB, Ansari HD, Hajek AM, Bageris A, Raffel TR. Large-scale spatial drivers of avian schistosomes in Northern Michigan inland lakes. Parasitology 2024; 151:495-505. [PMID: 38465379 PMCID: PMC11106508 DOI: 10.1017/s0031182024000337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 03/02/2024] [Accepted: 03/03/2024] [Indexed: 03/12/2024]
Abstract
Avian schistosomes are snail-borne trematode parasites (Trichobilharzia spp.) that can cause a nasty skin rash in humans when their cercariae mistake us for their normal bird hosts. We sought to investigate drivers of the spatial distribution of Trichobilharzia cercaria abundance throughout Northern Michigan lakes. For 38 sites on 16 lakes, we assessed several dozen potential environmental predictors that we hypothesized might have direct or indirect effects on overall cercaria abundance, based on known relationships between abiotic and biotic factors in wetland ecosystems. We included variables quantifying local densities of intermediate hosts, temperature, periphyton growth rates, human land use and hydrology. We also measured daily abundance of schistosome cercariae in the water over a 5-week period, supported by community scientists who collected and preserved filtered water samples for qPCR. The strongest predictor of cercaria abundance was Lymnaea host snail density. Lymnaea density was higher in deeper lakes and at sites with more deciduous tree cover, consistent with their association with cool temperature habitats. Contrary to past studies of human schistosomes, we also found a significant negative relationship between cercaria abundance and submerged aquatic vegetation, possibly due to vegetation blocking cercaria movement from offshore snail beds. If future work shows that these effects are indeed causal, then these results suggest possible new approaches to managing swimmer's itch risk in northern MI lakes, such as modifying tree cover and shallow-water vegetation at local sites.
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Affiliation(s)
- Jason P. Sckrabulis
- Department of Biological Sciences, Oakland University, 118 Library Drive, 374 Dodge Hall, Rochester, MI 48309, USA
- Department of Biological Sciences, University of Notre Dame, 100 Galvin Life Science Center, Notre Dame, IN 46556, USA
| | - Madelyn L. Messner
- Department of Biological Sciences, Oakland University, 118 Library Drive, 374 Dodge Hall, Rochester, MI 48309, USA
| | - Jenna Stanny
- Department of Biological Sciences, Oakland University, 118 Library Drive, 374 Dodge Hall, Rochester, MI 48309, USA
| | - Ryan B. McWhinnie
- Department of Biological Sciences, Oakland University, 118 Library Drive, 374 Dodge Hall, Rochester, MI 48309, USA
| | - Hamzah D. Ansari
- Department of Chemistry, Oakland University, 146 Library Drive, 260 Mathematics and Science Center, Rochester, MI 48309, USA
| | - Aleena M. Hajek
- Department of Biological Sciences, Oakland University, 118 Library Drive, 374 Dodge Hall, Rochester, MI 48309, USA
| | - Alexander Bageris
- Department of Biological Sciences, Oakland University, 118 Library Drive, 374 Dodge Hall, Rochester, MI 48309, USA
| | - Thomas R. Raffel
- Department of Biological Sciences, Oakland University, 118 Library Drive, 374 Dodge Hall, Rochester, MI 48309, USA
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Blankespoor CL, Blankespoor HD, DeJong RJ. Swimmer's itch control: Timely waterfowl brood relocation significantly reduces an avian schistosome population and human cases on recreational lakes. PLoS One 2024; 19:e0288948. [PMID: 38359003 PMCID: PMC10868848 DOI: 10.1371/journal.pone.0288948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 01/18/2024] [Indexed: 02/17/2024] Open
Abstract
Swimmer's itch (SI) is a dermatitis in humans caused by cercariae of avian and mammalian schistosomes which emerge from infected snails on a daily basis. Mitigation methods for SI have long been sought with little success. Copper sulfate application to the water to kill the snail hosts is the historically employed method, but is localized, temporary, and harmful to many aquatic species. Here, we test an alternative method to control Trichobilharzia stagnicolae, a species well-known to cause SI in northern Michigan and elsewhere in North America. Summer relocation of broods of the only known vertebrate host, common merganser (Mergus merganser), greatly reduced snail infection prevalence the following year on two large, geographically separated lakes in northern Michigan. Subsequent years of host relocation achieved and maintained snail infection prevalence at ~0.05%, more than an order of magnitude lower than pre-intervention. A Before-After-Control-Intervention (BACI) study design using multiple-year snail infection data from two intervention lakes and three control lakes demonstrates that dramatic lake-wide reduction of an avian schistosome can be achieved and is not due to natural fluctuations in the parasite populations. The relevance of reducing snail infection prevalence is demonstrated by a large seven-year data set of SI incidence in swimmers at a high-use beach, which showed a substantial reduction in SI cases in two successive years after relocation began. In addition, data from another Michigan lake where vertebrate-host based intervention occurred in the 1980's are analyzed statistically and show a remarkably similar pattern of reduction in snail infection prevalence. Together, these results demonstrate a highly effective SI mitigation strategy that avoids the use of environmentally suspect chemicals and removes incentive for lethal host removal. Biologically, the results strongly suggest that T. stagnicolae is reliant on the yearly hatch of ducklings to maintain populations at high levels on a lake and that the role of migratory hosts in the spring and fall is much less significant.
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Affiliation(s)
- Curtis L. Blankespoor
- Science Department, Jackson College, Jackson, Michigan, United States of America
- University of Michigan Biological Station, Pellston, Michigan, United States of America
- Swimmer’s Itch Solutions, LLC, Adrian, Michigan, United States of America
| | - Harvey D. Blankespoor
- University of Michigan Biological Station, Pellston, Michigan, United States of America
- Swimmer’s Itch Solutions, LLC, Adrian, Michigan, United States of America
- Department of Biology, Hope College, Holland, Michigan, United States of America
| | - Randall J. DeJong
- University of Michigan Biological Station, Pellston, Michigan, United States of America
- Swimmer’s Itch Solutions, LLC, Adrian, Michigan, United States of America
- Department of Biology, Calvin University, Grand Rapids, Michigan, United States of America
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Soper DM, Raffel TR, Sckrabulis JP, Froelich KL, McPhail BA, Ostrowski MD, Reimink RL, Romano D, Rudko SP, Hanington PC. A novel schistosome species hosted by Planorbella (Helisoma) trivolvis is the most widespread swimmer's itch-causing parasite in Michigan inland lakes. Parasitology 2022; 150:1-10. [PMID: 36349562 PMCID: PMC10090624 DOI: 10.1017/s0031182022001561] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Revised: 09/29/2022] [Accepted: 10/14/2022] [Indexed: 11/11/2022]
Abstract
Cercarial dermatitis (‘swimmer's itch’; SI), characterized by small itchy bumps caused by schistosome parasites of birds and mammals, is a common problem in Michigan. Research on avian schistosomes began nearly 100 years ago in Michigan inland lakes, yet scientists are still uncovering basic biological information including the identification of local snail and parasite species that cause SI. Previous research primarily focused on lakes in the northern half of Michigan's lower peninsula, although SI occurs throughout the state. We surveyed snails and snail-borne trematodes in lakes across Michigan's lower peninsula and used quantitative polymerase chain reaction analysis of filtered water samples to identify parasites to the species level, including a recently discovered parasite species that uses the snail Planorbella (Helisoma) trivolvis as its intermediate host. Most SI mitigation efforts have focused on a parasite species hosted by the snail Lymnaea catescopium ( = Stagnicola emarginata); however, lymnaeid snails and their associated schistosome species were largely restricted to northern lakes. In contrast, P. trivolvis and its associated parasite species were common in both northern and southern Michigan lakes. A third schistosome species associated with physid snails was also present at low levels in both northern and southern lakes. These results indicate that the recently discovered parasite species and its planorbid snail intermediate host may be more important drivers of Michigan SI than previously thought, possibly due to increased definitive host abundance in recent decades. These results have potentially important implications for SI mitigation and control efforts.
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Affiliation(s)
- D. M. Soper
- Department of Biology, University of Dallas, 1845 E. Northgate Dr, Irving, TX 75062, USA
| | - T. R. Raffel
- Department of Biological Sciences, Oakland University, 118 Library Dr, Rochester Hills, MI 48309, USA
| | - J. P. Sckrabulis
- Department of Biological Sciences, Oakland University, 118 Library Dr, Rochester Hills, MI 48309, USA
| | - K. L. Froelich
- St. Joseph High School, 2521 Stadium Dr, St. Joseph, MI 49085, USA
- Freshwater Solutions LLC, 137 W 15th St, Holland, MI 49423, USA
- School of Public Health, University of Alberta, 357F South Academic Building, Edmonton, Alberta, Canada T6G 1C9
| | - B. A. McPhail
- School of Public Health, University of Alberta, 357F South Academic Building, Edmonton, Alberta, Canada T6G 1C9
| | - M. D. Ostrowski
- Department of Biological Sciences, Oakland University, 118 Library Dr, Rochester Hills, MI 48309, USA
| | - R. L. Reimink
- Freshwater Solutions LLC, 137 W 15th St, Holland, MI 49423, USA
- Office of Campus Ministries, Hope College, Holland, MI 49423, USA
| | - D. Romano
- Department of Biology, University of Dallas, 1845 E. Northgate Dr, Irving, TX 75062, USA
| | - S. P. Rudko
- Public Health Agency of Canada, Agence de la Santé Publique du Canada, 200 René-Lévesque Blvd., Montréal, Québec, Canada H2Z 1X4
| | - P. C. Hanington
- School of Public Health, University of Alberta, 357F South Academic Building, Edmonton, Alberta, Canada T6G 1C9
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Ebbs ET, Loker ES, Bu L, Locke SA, Tkach VV, Devkota R, Flores VR, Pinto HA, Brant SV. Phylogenomics and Diversification of the Schistosomatidae Based on Targeted Sequence Capture of Ultra-Conserved Elements. Pathogens 2022; 11:769. [PMID: 35890014 PMCID: PMC9321907 DOI: 10.3390/pathogens11070769] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 06/20/2022] [Accepted: 06/27/2022] [Indexed: 01/27/2023] Open
Abstract
Schistosomatidae Stiles and Hassall 1898 is a medically significant family of digenetic trematodes (Trematoda: Digenea), members of which infect mammals or birds as definitive hosts and aquatic or amphibious gastropods as intermediate hosts. Currently, there are 17 named genera, for many of which evolutionary interrelationships remain unresolved. The lack of a resolved phylogeny has encumbered our understanding of schistosomatid evolution, specifically patterns of host-use and the role of host-switching in diversification. Here, we used targeted sequence capture of ultra-conserved elements (UCEs) from representatives of 13 of the 17 named genera and 11 undescribed lineages that are presumed to represent either novel genera or species to generate a phylogenomic dataset for the estimation of schistosomatid interrelationships. This study represents the largest phylogenetic effort within the Schistosomatidae in both the number of loci and breadth of taxon sampling. We present a near-comprehensive family-level phylogeny providing resolution to several clades of long-standing uncertainty within Schistosomatidae, including resolution for the placement of the North American mammalian schistosomes, implying a second separate capture of mammalian hosts. Additionally, we present evidence for the placement of Macrobilharzia at the base of the Schistosoma + Bivitellobilharzia radiation. Patterns of definitive and intermediate host use and a strong role for intermediate host-switching are discussed relative to schistosomatid diversification.
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Affiliation(s)
- Erika T. Ebbs
- Department of Biology, Purchase College, The State University of New York, Purchase, NY 10577, USA
| | - Eric S. Loker
- Center for Evolutionary and Theoretical Immunology, Department of Biology, Museum of Southwestern Biology Parasite Division, University of New Mexico, Albuquerque, NM 87131, USA; (E.S.L.); (L.B.); (S.V.B.)
| | - Lijing Bu
- Center for Evolutionary and Theoretical Immunology, Department of Biology, Museum of Southwestern Biology Parasite Division, University of New Mexico, Albuquerque, NM 87131, USA; (E.S.L.); (L.B.); (S.V.B.)
| | - Sean A. Locke
- Department of Biology, University of Puerto Rico at Mayagüez, Box 9000, Mayagüez 00681-9000, Puerto Rico;
| | - Vasyl V. Tkach
- Grand Forks Department of Biology, University of North Dakota, Grand Forks, ND 58202, USA;
| | - Ramesh Devkota
- Vance Granville Community College, Henderson, NC 27536, USA;
| | - Veronica R. Flores
- Laboratorio de Parasitología, INIBIOMA (CONICET-Universidad Nacional del Comahue), Quintral 1250, San Carlos de Bariloche 8400, Argentina;
| | - Hudson A. Pinto
- Department of Parasitology, Institute of Biological Science, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, Brazil;
| | - Sara V. Brant
- Center for Evolutionary and Theoretical Immunology, Department of Biology, Museum of Southwestern Biology Parasite Division, University of New Mexico, Albuquerque, NM 87131, USA; (E.S.L.); (L.B.); (S.V.B.)
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The Tails of Two Avian Schistosomes: Paired Exposure Study Demonstrates Trichobilharzia stagnicolae Penetrates Human Skin More Readily than a Novel Avian Schistosome from Planorbella. Pathogens 2022; 11:pathogens11060651. [PMID: 35745505 PMCID: PMC9228815 DOI: 10.3390/pathogens11060651] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 05/31/2022] [Accepted: 05/31/2022] [Indexed: 12/10/2022] Open
Abstract
A novel schistosome from Planorbella snails currently known as avian schistosomatid sp. C (ASC) was recently described as being capable of causing the papules associated with swimmer’s itch. We conducted a paired study with 24 human volunteers, exposing each of their forearms to five drops of water containing cercariae of ASC or Trichobilharzia stagnicolae, and examined the skin for papules 1–3 days later. A mixed effects model showed that only the parasite species significantly affected the number of papules, while prior experimental exposure, swimming history, and swimmer’s itch experience did not. The total number of papules produced by the two species were very different: ASC produced a total of 2 papules from the 298 cercariae used, compared to 49 papules from 160 T. stagnicolae cercariae, a difference factor of more than 43X, which was comparable to the odds ratio of 45.5 computed using the statistical model. A well-known agent of swimmer’s itch, T. stagnicolae, is able to penetrate human skin more frequently than ASC, likely meaning that ASC is only a minor cause of swimmer’s itch where T. stagnicolae is present. We also completed limited experiments that compared the cercarial behavior of the two species in vitro and in situ. A known stimulant of schistosome cercarial penetration, α-linolenic acid, did not stimulate ASC cercariae to initiate penetration-associated behaviors as frequently as T. stagnicolae. However, when placed on esophageal tissue of the known vertebrate host for ASC, Canada goose (Branta canadensis), ASC cercariae were observed penetrating the esophageal epithelium quickly, whereas T. stagnicolae cercariae did not exhibit any penetration behaviors.
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6
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Pinto HA, Tenório Mati VL, Melo AL, Brant SV. A putative new genus of avian schistosome transmitted by Biomphalaria straminea (Gastropoda: Planorbidae) in Brazil, with a discussion on the potential involvement in human cercarial dermatitis. Parasitol Int 2022; 90:102607. [PMID: 35659634 DOI: 10.1016/j.parint.2022.102607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 05/28/2022] [Accepted: 05/30/2022] [Indexed: 11/29/2022]
Abstract
Human cercarial dermatitis (HCD) caused by avian schistosomes is an emerging health issue in different parts of the world. Nevertheless, parasite diversity, life cycle, and involvement in HCD remain poorly known or neglected in South America. Herein, we reported data obtained during a long-term malacological survey carried out in Pampulha Reservoir, an urban eutrophic waterbody from Brazil between 2009 and 2012. An ocellate brevifurcate cercaria emerged from 55 of 16,235 (0.34%) specimens of Biomphalaria straminea. Samples of the cercariae were subjected to morphological, experimental, and molecular study (analysis of partial sequences of nuclear 28S and mitochondrial cox1 genes). The molecular analysis revealed that the larva corresponds to an avian schistosome; however, it does not correspond to any named genus. A close related isolate was previously reported in Biomphalaria sudanica from Kenya (molecular divergences of 0.54% and 9.62% for 28S and cox1, respectively). The morphology of this cercaria was compared with other avian schistosome larvae from Biomphalaria spp. Attempts to infect experimentally ducks (Cairina moschata) and mice revealed cutaneous manifestations after exposure to cercariae, but adult parasites were not obtained in these hosts. Phylogenetic analysis suggests this parasite is a putative new genus and species of avian schistosome. The potential involvement of the larvae herein described in cases of HCD in Brazil cannot be ruled out. Surprisingly, HCD was not reported in the country so far, which can be related to difficulties in its diagnosis in areas of overlap with human schistosomes.
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Affiliation(s)
- Hudson A Pinto
- Laboratório de Biologia de Trematoda, Department of Parasitology, Institute of Biological Science, Universidade Federal de Minas Gerais, Brazil.
| | - Vitor L Tenório Mati
- Department of Medicine, Universidade Federal de Lavras, Lavras, Minas Gerais, Brazil
| | - Alan L Melo
- Laboratório de Biologia de Trematoda, Department of Parasitology, Institute of Biological Science, Universidade Federal de Minas Gerais, Brazil
| | - Sara V Brant
- Museum of Southwestern Biology Division of Parasites, Department of Biology, University of New Mexico, Albuquerque, NM, USA
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Loker ES, DeJong RJ, Brant SV. Scratching the Itch: Updated Perspectives on the Schistosomes Responsible for Swimmer's Itch around the World. Pathogens 2022; 11:587. [PMID: 35631108 PMCID: PMC9144223 DOI: 10.3390/pathogens11050587] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 05/09/2022] [Accepted: 05/13/2022] [Indexed: 01/01/2023] Open
Abstract
Although most studies of digenetic trematodes of the family Schistosomatidae dwell on representatives causing human schistosomiasis, the majority of the 130 identified species of schistosomes infect birds or non-human mammals. The cercariae of many of these species can cause swimmer's itch when they penetrate human skin. Recent years have witnessed a dramatic increase in our understanding of schistosome diversity, now encompassing 17 genera with eight more lineages awaiting description. Collectively, schistosomes exploit 16 families of caenogastropod or heterobranch gastropod intermediate hosts. Basal lineages today are found in marine gastropods and birds, but subsequent diversification has largely taken place in freshwater, with some reversions to marine habitats. It seems increasingly likely that schistosomes have on two separate occasions colonized mammals. Swimmer's itch is a complex zoonotic disease manifested through several different routes of transmission involving a diversity of different host species. Swimmer's itch also exemplifies the value of adopting the One Health perspective in understanding disease transmission and abundance because the schistosomes involved have complex life cycles that interface with numerous species and abiotic components of their aquatic environments. Given the progress made in revealing their diversity and biology, and the wealth of questions posed by itch-causing schistosomes, they provide excellent models for implementation of long-term interdisciplinary studies focused on issues pertinent to disease ecology, the One Health paradigm, and the impacts of climate change, biological invasions and other environmental perturbations.
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Affiliation(s)
- Eric S. Loker
- Center for Evolutionary and Theoretical Immunology, Parasites Division, Museum of Southwestern Biology, Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA;
| | - Randall J. DeJong
- Department of Biology, Calvin University, Grand Rapids, MI 49546, USA;
| | - Sara V. Brant
- Center for Evolutionary and Theoretical Immunology, Parasites Division, Museum of Southwestern Biology, Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA;
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McPhail BA, Froelich K, Reimink RL, Hanington PC. Simplifying Schistosome Surveillance: Using Molecular Cercariometry to Detect and Quantify Cercariae in Water. Pathogens 2022; 11:pathogens11050565. [PMID: 35631086 PMCID: PMC9146278 DOI: 10.3390/pathogens11050565] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 05/05/2022] [Accepted: 05/06/2022] [Indexed: 11/16/2022] Open
Abstract
Avian schistosomes are considered a public health nuisance due to their ability to cause swimmer’s itch when accidentally encountering humans rather than their intended avian hosts. Researchers have been monitoring their presence and abundance through snail collections and cercariometry. Cercariometry methods have evolved over the last several decades to detect individual schistosome species from a single water sample, simplifying the monitoring of these parasites. This methodological evolution coincides with the development of the field of environmental DNA (eDNA) where genetic material is extracted from environmental samples, rather than individual organisms. While there are some limitations with using molecular cercariometry, notably the cost and its inability to differentiate between life cycle stages, it substantially reduces the labor required to study trematode populations. It also can be used in complement with snail collections to understand the composition of avian schistosomes in an environment.
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Affiliation(s)
- Brooke A. McPhail
- School of Public Health, University of Alberta, 357 South Academic Building, 116 St. and 85th Ave., Edmonton, AB T6G 2R3, Canada; (B.A.M.); (K.F.)
| | - Kelsey Froelich
- School of Public Health, University of Alberta, 357 South Academic Building, 116 St. and 85th Ave., Edmonton, AB T6G 2R3, Canada; (B.A.M.); (K.F.)
- Freshwater Solutions LLC, 137 W 15th St., Holland, MI 49423, USA;
- Saint Joseph High School, 2521 Stadium Dr., Saint Joseph, MI 49085, USA
| | - Ronald L. Reimink
- Freshwater Solutions LLC, 137 W 15th St., Holland, MI 49423, USA;
- Office of Campus Ministries, 110 E. 12th St. Hope College, Holland, MI 49423, USA
| | - Patrick C. Hanington
- School of Public Health, University of Alberta, 357 South Academic Building, 116 St. and 85th Ave., Edmonton, AB T6G 2R3, Canada; (B.A.M.); (K.F.)
- Correspondence:
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9
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Rudko SP, McPhail BA, Reimink RL, Froelich K, Turnbull A, Hanington PC. Non-resident definitive host presence is sufficient to sustain avian schistosome populations. Int J Parasitol 2022; 52:305-315. [PMID: 35007566 DOI: 10.1016/j.ijpara.2021.11.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 11/29/2021] [Accepted: 11/30/2021] [Indexed: 11/27/2022]
Abstract
To control swimmer's itch in northern Michigan inland lakes, USA, one species of bird, the common merganser (Mergus merganser), has been relocated from several lakes since 2015. Relocation efforts are driven by a desire to reduce the prevalence of the swimmer's itch-causing parasite Trichobilharzia stagnicolae. The intention of this state-sponsored control effort was to interrupt the life cycle of T. stagnicolae and reduce parasite egg contribution into the environment from summer resident mergansers such that infections of the intermediate snail host Stagnicola emarginata declined. Reduced snail infection prevalence was expected to substantially reduce the abundance of the swimmer's itch-causing cercarial stage of the parasite in water. With no official program in place to assess the success of this relocation effort, we sought to study the effectiveness and impact of the removal of a single definitive host from a location with high definitive host and parasite diversity. This was assessed through a comprehensive, lake-wide monitoring study measuring longitudinal changes in the abundance of three species of avian schistosome cercariae in four inland Michigan lakes. Environmental measurements were also taken at these lakes to understand how they can affect swimmer's itch incidence. This study demonstrates that the diversity of avian schistosomes at the study lakes would likely make targeting a single species of swimmer's itch-causing parasite meaningless from a swimmer's itch control perspective. Our data also suggest that removing the common merganser is not an effective control strategy for the T. stagnicolae parasite, likely due to contributions of the parasite made by non-resident birds, possibly migrants, in the autumn and spring. It appears likely that only minimal contact time between the definitive host and the lake ecosystem is required to contribute sufficient parasite numbers to maintain a thriving population of parasite species with high host specificity.
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Affiliation(s)
- Sydney P Rudko
- Public Health Agency of Canada, Agence de la Santé Publique du Canada, 200 René-Lévesque Blvd., Montréal, Québec, H2Z 1X4, Canada
| | - Brooke A McPhail
- School of Public Health, University of Alberta, 357F South Academic Building, 116 St. and 85th Ave., Alberta T6G 2R3, Canada
| | - Ronald L Reimink
- Office of Campus Ministries, 110 E. 12th St. Hope College, Holland, MI, 49423, United States; Freshwater Solutions LLC, 137 W 15(th) St., Holland, MI, 49423, United States
| | - Kelsey Froelich
- School of Public Health, University of Alberta, 357F South Academic Building, 116 St. and 85th Ave., Alberta T6G 2R3, Canada; Freshwater Solutions LLC, 137 W 15(th) St., Holland, MI, 49423, United States; Saint Joseph High School, 2521 Stadium Dr., Saint Joseph, MI, 49085, United States
| | - Alyssa Turnbull
- School of Public Health, University of Alberta, 357F South Academic Building, 116 St. and 85th Ave., Alberta T6G 2R3, Canada
| | - Patrick C Hanington
- School of Public Health, University of Alberta, 357F South Academic Building, 116 St. and 85th Ave., Alberta T6G 2R3, Canada.
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