title: Real-time PCR and sequencing assays for rapid detection and identification of avian schistosomes in environmental samples.
abstract: Cercarial dermatitis, also known as swimmer's itch, is an allergenic skin reaction followed by intense itching caused by schistosome cercariae penetrating human skin. Cercarial dermatitis outbreaks occur globally and are frequently associated with freshwater lakes and are occasionally associated with marine or estuarine waters where birds reside year-round or where migratory birds reside. In this study, a broadly reactive TaqMan assay targeting 18S rRNA gene (ribosomal DNA [rDNA]) sequences that was based on a genetically diverse panel of schistosome isolates representing 13 genera and 20 species (the 18S rDNA TaqMan assay) was developed. A PCR assay was also developed to amplify a 28S rDNA region for subsequent sequencing to identify schistosomes. When applied to surface water samples seeded with Schistosoma mansoni cercariae, the 18S rDNA TaqMan assay enabled detection at a level of 5 S. mansoni cercariae in 100 liters of lake water. The 18S rDNA TaqMan and 28S rDNA PCR sequencing assays were also applied to 100-liter water samples collected from lakes in Nebraska and Wisconsin where there were reported dermatitis outbreaks. Avian schistosome DNA was detected in 11 of 34 lake water samples using the TaqMan assay. Further 28S rDNA sequence analysis of positive samples confirmed the presence of avian schistosome DNA and provided a preliminary identification of the avian schistosomes in 10 of the 11 samples. These data indicate that the broadly schistosome-reactive TaqMan assay can be effective for rapid screening of large-volume water samples for detection of avian schistosomes, thereby facilitating timely response actions to mitigate or prevent dermatitis outbreaks. Additionally, samples positive by the 18S rDNA TaqMan assay can be further assayed using the 28S rDNA sequencing assay to both confirm the presence of schistosomes and contribute to their identification.
authors: Waterborne Disease Prevention Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA jin2@cdc.gov.
authors: Narayanan
authors: N
authors: Jothikumar
authors: Food and Waterborne Disease Program, Bureau of Epidemiology, Florida Department of Health, Tallahassee, Florida, USA.
authors: Bonnie J
authors: BJ
authors: Mull
authors: Department of Biology, COBRE Center for Evolutionary and Theoretical Immunology, Museum of Southwestern Biology, Division of Parasitology, University of New Mexico, Albuquerque, New Mexico, USA.
authors: Sara V
authors: SV
authors: Brant
authors: Department of Biology, COBRE Center for Evolutionary and Theoretical Immunology, Museum of Southwestern Biology, Division of Parasitology, University of New Mexico, Albuquerque, New Mexico, USA.
authors: Eric S
authors: ES
authors: Loker
authors: Central District Health Department, Grand Island, Nebraska, USA.
authors: Jeremy
authors: J
authors: Collinson
authors: Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors: W Evan
authors: WE
authors: Secor
authors: Waterborne Disease Prevention Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors: Vincent R
authors: VR
authors: Hill
mesh_terms: D000818:Animals; D001483:Base Sequence; D001715:Bird Diseases / Q000469:parasitology; D001717:Birds / Q000469:parasitology*; D004275:DNA, Ribosomal / Q000235:genetics; D004783:Environmental Microbiology; D005618:Fresh Water / Q000469:parasitology*; D006801:Humans; D057230:Limit of Detection; D008969:Molecular Sequence Data; D009329:Nebraska; D010802:Phylogeny; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D012551:Schistosomatidae / Q000235:genetics / Q000302:isolation & purification*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA / Q000379:methods*; D012876:Skin Diseases, Parasitic / Q000175:diagnosis / Q000517:prevention & control; D014201:Trematode Infections / Q000469:parasitology / Q000662:veterinary; D014922:Wisconsin
chemical_list: D004275:DNA, Ribosomal