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John E Madigan - One of the best experts on this subject based on the ideXlab platform.
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Digenetic trematodes, Acanthatrium sp. and Lecithodendrium sp., as vectors of Neorickettsia risticii, the agent of Potomac Horse Fever.
Journal of Helminthology, 2003Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, John E MadiganAbstract:Neorickettsia (formerly Ehrlichia) risticii, the agent of Potomac Horse Fever (PHF), has been recently detected in trematode stages found in the secretions of freshwater snails and in aquatic insects. Insectivores, such as bats and birds, may serve as the definitive host of the trematode vector. To determine the definitive helminth vector, five bats (Myotis yumanensis) and three swallows (Hirundo rustica, Tachycineta bicolor) were collected from a PHF endemic location in northern California. Bats and swallows were dissected and their major organs examined for trematodes and for N. risticii DNA using a nested polymerase chain reaction (PCR) assay. Adult digenetic trematodes, Acanthatrium sp. and/or Lecithodendrium sp., were recovered from the gastrointestinal tract of all bats and from one swallow. The intestine of three bats, the spleen of two bats and one swallow as well as the liver of one swallow tested PCR positive for N. risticii. From a total of seven pools of identical digenetic trematodes collected from single hosts, two pools of Acanthatrium sp. and one pool of Lecithodendrium sp. tested PCR positive. The results of this investigation provide preliminary evidence that at least two trematodes in the family Lecithodendriidae are vectors of N. risticii. The data also suggest that bats and swallows not only act as a host for trematodes but also as a possible natural reservoir for N. risticii.
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Molecular detection of an Ehrlichia-like agent in rainbow trout (Oncorhynchus mykiss) from Northern California.
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Elfriede Derock, Mel Willis, Ronald P. Hedrick, John E MadiganAbstract:Ehrlichia DNA was identified by nested PCR in rainbow trout (Oncorhynchus mykiss) collected from a creek in northern California where Potomac Horse Fever is endemic. Ehrlichia DNA was found in tissues from several organs including the gills, heart, spleen, liver, kidneys and intestine of trout and from three different adult digenetic trematodes (Deropegus sp., Crepidostomum sp., Creptotrema sp.) parasitizing the gallbladder and/or the intestine of the trout. Sequencing of PCR-amplified DNA from the 16S rRNA gene indicated that the source organism was most closely related to the sequences of E. risticii (level of sequence similarity 96.0%), the SF agent (95.9%), E. sennetsu (95.8%), and Neorickettsia helminthoeca (95.3%). The data suggest that trout and parasitic trematodes may be involved in the epidemiology of an Ehrlichia-like agent belonging to the E. sennetsu genogroup. Whether the fish agent infects Horses, dogs, or human beings, and whether it causes disease, remain to be determined.
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Infection rate of Ehrlichia risticii, the agent of Potomac Horse Fever, in freshwater stream snails (Juga yrekaensis) from northern California.
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Jeannine Berger Pusterla, Elfriede Derock, John E MadiganAbstract:Juga yrekaensis freshwater snails were tested for trematode stages and for Ehrlichia risticii DNA using a nested PCR assay. Snails were collected monthly from two Potomac Horse Fever (PHF) endemic locations in northern California (Montague and Weed). The trematode infection rate varied between 40 and 93.3% in large snails (shell size >15mm) and between 0 and 13.3% in small snails (
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infection rate of ehrlichia risticii the agent of Potomac Horse Fever in freshwater stream snails juga yrekaensis from northern california
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Jeannine Berger Pusterla, Elfriede Derock, John E MadiganAbstract:Juga yrekaensis freshwater snails were tested for trematode stages and for Ehrlichia risticii DNA using a nested PCR assay. Snails were collected monthly from two Potomac Horse Fever (PHF) endemic locations in northern California (Montague and Weed). The trematode infection rate varied between 40 and 93.3% in large snails (shell size >15mm) and between 0 and 13.3% in small snails (<15mm). The highest trematode infection rate for large and small snails was recorded in September and the lowest infection rate for large snails was recorded in June (Weed) and October (Montague). The E. risticii PCR infection rate among small snails from both sites was similar and varied monthly between 0 and 3.3%. The PCR infection rate for large snails from Weed was high in May (20.0%) and decreased progressively until November (10.0%). The PCR infection rate for large snails from Montague was 5.0% in May, 26.3% in August and 16. 7% in October. PCR-positive snails were always related to the microscopic detection of trematode stages (virgulate cercariae). This study provides evidence that J. yrekaensis are infected with trematode cercariae that harbor E. risticii. The number of snails harboring trematode stages and the number of PCR positive snails varied with the size of the snails, the month of collection, and the geographic origin.
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Infection of Aquatic Insects with Trematode Metacercariae Carrying Ehrlichia risticii, the Cause of Potomac Horse Fever
Journal of Medical Entomology, 2000Co-Authors: Joon-seok Chae, Nicola Pusterla, Eileen Johnson, Elfriede Derock, Sharon P. Lawler, John E MadiganAbstract:We provide evidence of Ehrlichia risticii Holland, the agent of Potomac Horse Fever, in trematode stages found in aquatic insects collected from a pasture stream in northern California, using nested polymerase chain reaction (PCR) amplification and sequence analyses of the 16S rRNA, 51 kDa major antigen and groEL heat shock protein genes. E. risticii was detected in metacercariae found in the immatures and adults of the following insects: caddisflies (Trichoptera), mayflies (Ephemeroptera), damselflies (Odonata, Zygoptera), dragonflies (Odonata, Anisoptera), and stoneflies (Plecoptera). The prevalence of E. risticii was 31.9% (n = 454 individuals) in aquatic insects (13 of 17 species were positive). Prevalence within orders was as follows: 43.5% (n = 207) in caddisflies, 15.2% (n = 92) in mayflies, 13.9% (n = 115) in damselflies, 10.0% (n = 10) in dragonflies, and 80.0% (n = 30) in stoneflies. This study demonstrates a broad intermediate host range for trematodes that act as vector for E. risticii. Insects are likely to play an important role in the epidemiology of this disease.
Yasuko Rikihisa - One of the best experts on this subject based on the ideXlab platform.
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Isolation and Molecular Analysis of a Novel Neorickettsia Species That Causes Potomac Horse Fever.
Mbio, 2020Co-Authors: Omid Teymournejad, John D. Baird, Luis G. Arroyo, Hannah Bekebrede, Mingqun Lin, Ahmed Kamr, Ramiro E. Toribio, Yasuko RikihisaAbstract:ABSTRACT Potomac Horse Fever (PHF), a severe and frequently fatal febrile diarrheal disease, has been known to be caused only by Neorickettsia risticii, an endosymbiont of digenean trematodes. Here, we report the cell culture isolation of a new Neorickettsia species found in two locations in eastern Ontario, Canada, in 2016 and 2017 (in addition to 10 variable strains of N. risticii) from N. risticii PCR-negative Horses with clinical signs of PHF. Gene sequences of 16S rRNA and the major surface antigen P51 of this new Neorickettsia species were distinct from those of all previously characterized N. risticii strains and Neorickettsia species, except for those from an uncharacterized Neorickettsia species culture isolate from a Horse with PHF in northern Ohio in 1991. The new Neorickettsia species nonetheless had the characteristic intramolecular repeats within strain-specific antigen 3 (Ssa3), which were found in all sequenced Ssa3s of N. risticii strains. Experimental inoculation of two naive ponies with the new Neorickettsia species produced severe and subclinical PHF, respectively, and the bacteria were reisolated from both of them, fulfilling Koch’s postulates. Serological assay titers against the new Neorickettsia species were higher than those against N. risticii. Whole-genome sequence analysis of the new Neorickettsia species revealed unique features of this bacterium compared with N. risticii. We propose to classify this new bacterium as Neorickettsia finleia sp. nov. This finding will improve the laboratory diagnosis of and vaccine for PHF, environmental risk assessment of PHF, and understanding of PHF pathogenesis and Neorickettsia biology in general. IMPORTANCE Despite the detection of Neorickettsia species DNA sequences in various trematode species and their hosts, only three Neorickettsia species have been cell culture isolated and whole-genome sequenced and are known to infect mammals and/or cause disease. The molecular mechanisms that enable the obligatory intracellular bacterium Neorickettsia to colonize trematodes and to horizontally transmit from trematodes to mammals, as well as the virulence factors associated with specific mammalian hosts, are unknown. Potomac Horse Fever (PHF) is a severe and acute systemic infectious disease of Horses, with clinical signs that include diarrhea. Neorickettsia risticii is the only known bacterial species that causes PHF. Ingestion of insects harboring N. risticii-infected trematodes by Horses leads to PHF. Our discovery of a new Neorickettsia species that causes PHF and whole-genome sequence analysis of this bacterium will improve laboratory diagnosis and vaccine development for PHF and will contribute to our understanding of Neorickettsia ecology, pathogenesis, and biology.
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An Ecotype of Neorickettsia risticii Causing Potomac Horse Fever in Canada.
Applied and Environmental Microbiology, 2016Co-Authors: Qingming Xiong, John D. Baird, Luis G. Arroyo, Hannah Bekebrede, Pratibha Sharma, Yasuko RikihisaAbstract:ABSTRACT Neorickettsia (formerly Ehrlichia) risticii is an obligatory intracellular bacterium of digenetic trematodes. When a Horse accidentally ingests aquatic insects containing encysted trematodes infected with N. risticii, the bacterium is transmitted from trematodes to Horse cells and causes an acute and often fatal disease called Potomac Horse Fever (PHF). Since the discovery of N. risticii in the United States in 1984, using immunofluorescence and PCR assays, PHF has been increasingly recognized throughout North America and South America. However, so far, there exist only a few stable N. risticii culture isolates, all of which are from Horses within the United States, and the strain diversity and environmental spreading and distribution of pathogenic N. risticii strains remain poorly understood. This paper reports the isolation of N. risticii from the blood of a Horse with acute PHF in Ontario, Canada. Intracellular N. risticii colonies were detected in P388D1 cells after 47 days of culturing and 8 days after the addition of rapamycin. Molecular phylogenetic analysis based on amino acid sequences of major surface proteins P51 and Ssa1 showed that this isolate is distinct from any previously sequenced strains but closely related to midwestern U.S. strains. This is the first Canadian strain cultured, and a new method was developed to reactivate dormant N. risticii to improve culture isolation. IMPORTANCENeorickettsia risticii is an environmental bacterium that lives inside flukes that are parasitic to aquatic snails, insects, and bats. When a Horse accidentally ingests insects harboring flukes infected with N. risticii, the bacterium is transmitted to the Horse and causes an acute and often fatal disease called Potomac Horse Fever. Although the disease has been increasingly recognized throughout North and South America, N. risticii has not been cultured outside the United States. This paper reports the first Canadian strain cultured and a new method to effectively culture isolate N. risticii from the Horse blood sample. Molecular analysis showed that the genotype of this Canadian strain is distinct from previously sequenced strains but closely related to midwestern U.S. strains. Culture isolation of N. risticii strains would confirm the geographic presence of pathogenic N. risticii, help elucidate N. risticii strain diversity and environmental spreading and distribution, and improve diagnosis and development of vaccines for this dreadful disease.
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Neorickettsia risticii surface-exposed proteins: proteomics identification, recognition by naturally-infected Horses, and strain variations
Veterinary Research, 2011Co-Authors: Kathryn E. Gibson, Gabrielle Pastenkos, Susanne Moesta, Yasuko RikihisaAbstract:Neorickettsia risticii is the Gram-negative, obligate, and intracellular bacterial pathogen responsible for Potomac Horse Fever (PHF): an important acute systemic disease of Horses. N. risticii surface proteins, critical for immune recognition, have not been thoroughly characterized. In this paper, we identified the 51-kDa antigen (P51) as a major surface-exposed outer membrane protein of older and contemporary strains of N. risticii through mass spectrometry of streptavidin-purified biotinylated surface-labeled proteins. Western blot analysis of sera from naturally-infected Horses demonstrated universal and strong recognition of recombinant P51 over other Neorickettsia recombinant proteins. Comparisons of amino acid sequences for predicted secondary structures of P51, as well as Neorickettsia surface proteins 2 (Nsp2) and 3 (Nsp3) among N. risticii strains from Horses with PHF during a 26-year period throughout the United States revealed that the majority of variations among strains were concentrated in regions predicted to be external loops of their β-barrel structures. Large insertions or deletions occurred within a tandem-repeat region in Ssa3. These data demonstrate patterns of geographical association for P51 and temporal associations for Nsp2, Nsp3, and Ssa3, indicating evolutionary trends for these Neorickettsia surface antigen genes. This study showed N. risticii surface protein population dynamics, providing groundwork for designing immunodiagnostic targets for PHF.
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Analysis of complete genome sequence of Neorickettsia risticii: causative agent of Potomac Horse Fever
Nucleic Acids Research, 2009Co-Authors: Mingqun Lin, Chunbin Zhang, Kathryn E. Gibson, Yasuko RikihisaAbstract:Neorickettsia risticii is an obligate intracellular bacterium of the trematodes and mammals. Horses develop Potomac Horse Fever (PHF) when they ingest aquatic insects containing encysted N. risticii-infected trematodes. The complete genome sequence of N. risticii Illinois consists of a single circular chromosome of 879 977 bp and encodes 38 RNA species and 898 proteins. Although N. risticii has limited ability to synthesize amino acids and lacks many metabolic pathways, it is capable of making major vitamins, cofactors and nucleotides. Comparison with its closely related human pathogen N. sennetsu showed that 758 (88.2%) of protein-coding genes are conserved between N. risticii and N. sennetsu. Four-way comparison of genes among N. risticii and other Anaplasmataceae showed that most genes are either shared among Anaplasmataceae (525 orthologs that generally associated with housekeeping functions), or specific to each genome (>200 genes that are mostly hypothetical proteins). Genes potentially involved in the pathogenesis of N. risticii were identified, including those encoding putative outer membrane proteins, two-component systems and a type IV secretion system (T4SS). The bipolar localization of T4SS pilus protein VirB2 on the bacterial surface was demonstrated for the first time in obligate intracellular bacteria. These data provide insights toward genomic potential of N. risticii and intracellular parasitism, and facilitate our understanding of PHF pathogenesis.
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Molecular link of different stages of the trematode host of Neorickettsia risticii to Acanthatrium oregonense.
Environmental Microbiology, 2008Co-Authors: Kathryn E. Gibson, Yasuko RikihisaAbstract:Summary Neorickettsia risticii, the obligatory intracellular bacterium that causes Potomac Horse Fever, has been detected in various developmental stages of digenetic trematodes in the environment. Neorickettsia risticii-infected gravid trematodes were identified as Acanthatrium oregonense, based on morphologic keys. However, whether immature trematodes harbouring N. risticii are also A. oregonense was unknown. The objective of this study was to infer the life cycle of N. risticii-positive trematode hosts and transstadial transmission of the bacterium by molecularly characterizing the relationship among adult and immature stages of trematodes confirmed infected with N. risticii. Sequences of 18S ribosomal RNA genes up to 1922 bp in size were obtained from infected adult gravid trematodes, sporocysts and cercariae, and metacercariae. The sequences from the different immature stages of trematode are closely related to those of adult trematodes, some with 100% sequence identity; thus, they likely are life stages of A. oregonense. Comparisons with known 18S ribosomal RNA gene sequences of other digenetic trematodes indicated that all tested stages of the N. risticii-positive trematodes belong to the family Lecithodendriidae, supporting the morphological identification.
Nicola Pusterla - One of the best experts on this subject based on the ideXlab platform.
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Two cases of Neorickettsia (Ehrlichia) risticii infection in Horses from Nova Scotia.
Canadian Veterinary Journal-revue Veterinaire Canadienne, 2004Co-Authors: Meera C. Heller, Nicola Pusterla, Jeannine Berger Pusterla, J.t. Mcclure, Simone StahelAbstract:Two Horses from Nova Scotia were diagnosed with Potomac Horse Fever (PHF). Polymerase chain reaction analysis was performed on formalin-fixed colon tissue or whole blood to show the presence of Neorickettsia risticii DNA, the causative agent of PHF. These are the first reported cases of PHF in the Maritime Provinces.
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Digenetic trematodes, Acanthatrium sp. and Lecithodendrium sp., as vectors of Neorickettsia risticii, the agent of Potomac Horse Fever.
Journal of Helminthology, 2003Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, John E MadiganAbstract:Neorickettsia (formerly Ehrlichia) risticii, the agent of Potomac Horse Fever (PHF), has been recently detected in trematode stages found in the secretions of freshwater snails and in aquatic insects. Insectivores, such as bats and birds, may serve as the definitive host of the trematode vector. To determine the definitive helminth vector, five bats (Myotis yumanensis) and three swallows (Hirundo rustica, Tachycineta bicolor) were collected from a PHF endemic location in northern California. Bats and swallows were dissected and their major organs examined for trematodes and for N. risticii DNA using a nested polymerase chain reaction (PCR) assay. Adult digenetic trematodes, Acanthatrium sp. and/or Lecithodendrium sp., were recovered from the gastrointestinal tract of all bats and from one swallow. The intestine of three bats, the spleen of two bats and one swallow as well as the liver of one swallow tested PCR positive for N. risticii. From a total of seven pools of identical digenetic trematodes collected from single hosts, two pools of Acanthatrium sp. and one pool of Lecithodendrium sp. tested PCR positive. The results of this investigation provide preliminary evidence that at least two trematodes in the family Lecithodendriidae are vectors of N. risticii. The data also suggest that bats and swallows not only act as a host for trematodes but also as a possible natural reservoir for N. risticii.
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Molecular detection of an Ehrlichia-like agent in rainbow trout (Oncorhynchus mykiss) from Northern California.
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Elfriede Derock, Mel Willis, Ronald P. Hedrick, John E MadiganAbstract:Ehrlichia DNA was identified by nested PCR in rainbow trout (Oncorhynchus mykiss) collected from a creek in northern California where Potomac Horse Fever is endemic. Ehrlichia DNA was found in tissues from several organs including the gills, heart, spleen, liver, kidneys and intestine of trout and from three different adult digenetic trematodes (Deropegus sp., Crepidostomum sp., Creptotrema sp.) parasitizing the gallbladder and/or the intestine of the trout. Sequencing of PCR-amplified DNA from the 16S rRNA gene indicated that the source organism was most closely related to the sequences of E. risticii (level of sequence similarity 96.0%), the SF agent (95.9%), E. sennetsu (95.8%), and Neorickettsia helminthoeca (95.3%). The data suggest that trout and parasitic trematodes may be involved in the epidemiology of an Ehrlichia-like agent belonging to the E. sennetsu genogroup. Whether the fish agent infects Horses, dogs, or human beings, and whether it causes disease, remain to be determined.
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Infection rate of Ehrlichia risticii, the agent of Potomac Horse Fever, in freshwater stream snails (Juga yrekaensis) from northern California.
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Jeannine Berger Pusterla, Elfriede Derock, John E MadiganAbstract:Juga yrekaensis freshwater snails were tested for trematode stages and for Ehrlichia risticii DNA using a nested PCR assay. Snails were collected monthly from two Potomac Horse Fever (PHF) endemic locations in northern California (Montague and Weed). The trematode infection rate varied between 40 and 93.3% in large snails (shell size >15mm) and between 0 and 13.3% in small snails (
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infection rate of ehrlichia risticii the agent of Potomac Horse Fever in freshwater stream snails juga yrekaensis from northern california
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Jeannine Berger Pusterla, Elfriede Derock, John E MadiganAbstract:Juga yrekaensis freshwater snails were tested for trematode stages and for Ehrlichia risticii DNA using a nested PCR assay. Snails were collected monthly from two Potomac Horse Fever (PHF) endemic locations in northern California (Montague and Weed). The trematode infection rate varied between 40 and 93.3% in large snails (shell size >15mm) and between 0 and 13.3% in small snails (<15mm). The highest trematode infection rate for large and small snails was recorded in September and the lowest infection rate for large snails was recorded in June (Weed) and October (Montague). The E. risticii PCR infection rate among small snails from both sites was similar and varied monthly between 0 and 3.3%. The PCR infection rate for large snails from Weed was high in May (20.0%) and decreased progressively until November (10.0%). The PCR infection rate for large snails from Montague was 5.0% in May, 26.3% in August and 16. 7% in October. PCR-positive snails were always related to the microscopic detection of trematode stages (virgulate cercariae). This study provides evidence that J. yrekaensis are infected with trematode cercariae that harbor E. risticii. The number of snails harboring trematode stages and the number of PCR positive snails varied with the size of the snails, the month of collection, and the geographic origin.
Joon-seok Chae - One of the best experts on this subject based on the ideXlab platform.
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Protein of Neorickettsia risticii NR-JA1
2015Co-Authors: John-hwa Lee, Joon-seok ChaeAbstract:ABSTRACT: Neorickettsia (Ehrlichia) risticii is a causative agent of acute diar-rheal syndrome in Horses, commonly known as Potomac Horse Fever. Korean isolate of N. risticii NR-JA1 was cultivated in mouse macrophage cell line P388D1. A complete ORF of p51 antigenic protein gene was amplified and cloned into pQE32 and pcDNA3.1 vectors and the resultant clones were named as pQE32/Nr-51 and pcDNA3.1/Nr-51, respectively. Recombinant p51 (rp51) protein antigen was expressed in E. coli (pQE32/Nr-51) and cos-7 cell line (pcDNA3.1/Nr-51). The rp51 protein showed immunoreactivity with anti-mouse p51 antibodies. BALB/c mice were inoculated with recombinant plas-mid DNA (pcDNA3.1/Nr-51). The serum samples collected from these BALB/c mice showed IgG ELISA titers of 1:128. In a Western immunoblot assay, these serum samples showed a strong reactivity to rp51 expressed in cos-7 cell line transfected with pcDNA3.1/Nr-51. The results of this preliminary indicate that N. risticii p51 protein is an immmuno-dominant antigen and may be a good tar-get for the development of serological or a molecular diagnostic test and possi-bly an improved recombinant DNA based vaccine against Potomac Horse Fever
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Digenetic trematodes, Acanthatrium sp. and Lecithodendrium sp., as vectors of Neorickettsia risticii, the agent of Potomac Horse Fever.
Journal of Helminthology, 2003Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, John E MadiganAbstract:Neorickettsia (formerly Ehrlichia) risticii, the agent of Potomac Horse Fever (PHF), has been recently detected in trematode stages found in the secretions of freshwater snails and in aquatic insects. Insectivores, such as bats and birds, may serve as the definitive host of the trematode vector. To determine the definitive helminth vector, five bats (Myotis yumanensis) and three swallows (Hirundo rustica, Tachycineta bicolor) were collected from a PHF endemic location in northern California. Bats and swallows were dissected and their major organs examined for trematodes and for N. risticii DNA using a nested polymerase chain reaction (PCR) assay. Adult digenetic trematodes, Acanthatrium sp. and/or Lecithodendrium sp., were recovered from the gastrointestinal tract of all bats and from one swallow. The intestine of three bats, the spleen of two bats and one swallow as well as the liver of one swallow tested PCR positive for N. risticii. From a total of seven pools of identical digenetic trematodes collected from single hosts, two pools of Acanthatrium sp. and one pool of Lecithodendrium sp. tested PCR positive. The results of this investigation provide preliminary evidence that at least two trematodes in the family Lecithodendriidae are vectors of N. risticii. The data also suggest that bats and swallows not only act as a host for trematodes but also as a possible natural reservoir for N. risticii.
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Identification of trematode cercariae carrying Neorickettsia risticii in freshwater stream snails.
Annals of the New York Academy of Sciences, 2003Co-Authors: Bae Keun Park, Meen‐ju Kim, Eun-ha Kim, Min-seok Kim, Joon-seok ChaeAbstract:: We provide evidence of Neorickettsia (Ehrlichia) risticii Holland, the agent of Potomac Horse Fever, in trematode larval stages found in aquatic snails and insects collected from a stream in Korea, using nested polymerase chain reaction (PCR) and sequence analysis of the 16S rRNA gene fragment amplified from several cercaria species. It was observed that of 423 (13.1%) of 3,219 snails infected with cercariae, 77 (20.8% of the 371) were infected with N. risticii. Five families of trematode cercariae, Schistosomatidae, Echimostomatidae, Heterophyidae, Microphallidae, and Acanthocopidae were identified morphologically within Semisulcospira libertina, Radix auricularia coreana, and S. gottschei snails. Echinostoma cinetorchis, E. hortense, and Metagonimus sp. were identified based on both the cercarial morphology as well as by phylogenetic analysis of the amplified 18S rRNA gene sequences. Adult aquatic insects were also collected from the same sites and were sorted into five species, Ischnura asiatica in Coenagrionidae and Calopteryx japonica, Sympetrum darwinianum, Symptrum eroticum, and Symptrum parvulum in Calopterygoidae. One thousand and two hundred eighty five metacercariae (classified into groups A through F) were isolated from 310 adult aquatic insects, and the average number of metacercariae per aquatic insect was 4.1. However, there was no amplification of N. risticii from these metacercariae.
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Molecular detection of an Ehrlichia-like agent in rainbow trout (Oncorhynchus mykiss) from Northern California.
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Elfriede Derock, Mel Willis, Ronald P. Hedrick, John E MadiganAbstract:Ehrlichia DNA was identified by nested PCR in rainbow trout (Oncorhynchus mykiss) collected from a creek in northern California where Potomac Horse Fever is endemic. Ehrlichia DNA was found in tissues from several organs including the gills, heart, spleen, liver, kidneys and intestine of trout and from three different adult digenetic trematodes (Deropegus sp., Crepidostomum sp., Creptotrema sp.) parasitizing the gallbladder and/or the intestine of the trout. Sequencing of PCR-amplified DNA from the 16S rRNA gene indicated that the source organism was most closely related to the sequences of E. risticii (level of sequence similarity 96.0%), the SF agent (95.9%), E. sennetsu (95.8%), and Neorickettsia helminthoeca (95.3%). The data suggest that trout and parasitic trematodes may be involved in the epidemiology of an Ehrlichia-like agent belonging to the E. sennetsu genogroup. Whether the fish agent infects Horses, dogs, or human beings, and whether it causes disease, remain to be determined.
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Infection rate of Ehrlichia risticii, the agent of Potomac Horse Fever, in freshwater stream snails (Juga yrekaensis) from northern California.
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Jeannine Berger Pusterla, Elfriede Derock, John E MadiganAbstract:Juga yrekaensis freshwater snails were tested for trematode stages and for Ehrlichia risticii DNA using a nested PCR assay. Snails were collected monthly from two Potomac Horse Fever (PHF) endemic locations in northern California (Montague and Weed). The trematode infection rate varied between 40 and 93.3% in large snails (shell size >15mm) and between 0 and 13.3% in small snails (
Eileen Johnson - One of the best experts on this subject based on the ideXlab platform.
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Digenetic trematodes, Acanthatrium sp. and Lecithodendrium sp., as vectors of Neorickettsia risticii, the agent of Potomac Horse Fever.
Journal of Helminthology, 2003Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, John E MadiganAbstract:Neorickettsia (formerly Ehrlichia) risticii, the agent of Potomac Horse Fever (PHF), has been recently detected in trematode stages found in the secretions of freshwater snails and in aquatic insects. Insectivores, such as bats and birds, may serve as the definitive host of the trematode vector. To determine the definitive helminth vector, five bats (Myotis yumanensis) and three swallows (Hirundo rustica, Tachycineta bicolor) were collected from a PHF endemic location in northern California. Bats and swallows were dissected and their major organs examined for trematodes and for N. risticii DNA using a nested polymerase chain reaction (PCR) assay. Adult digenetic trematodes, Acanthatrium sp. and/or Lecithodendrium sp., were recovered from the gastrointestinal tract of all bats and from one swallow. The intestine of three bats, the spleen of two bats and one swallow as well as the liver of one swallow tested PCR positive for N. risticii. From a total of seven pools of identical digenetic trematodes collected from single hosts, two pools of Acanthatrium sp. and one pool of Lecithodendrium sp. tested PCR positive. The results of this investigation provide preliminary evidence that at least two trematodes in the family Lecithodendriidae are vectors of N. risticii. The data also suggest that bats and swallows not only act as a host for trematodes but also as a possible natural reservoir for N. risticii.
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Molecular detection of an Ehrlichia-like agent in rainbow trout (Oncorhynchus mykiss) from Northern California.
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Elfriede Derock, Mel Willis, Ronald P. Hedrick, John E MadiganAbstract:Ehrlichia DNA was identified by nested PCR in rainbow trout (Oncorhynchus mykiss) collected from a creek in northern California where Potomac Horse Fever is endemic. Ehrlichia DNA was found in tissues from several organs including the gills, heart, spleen, liver, kidneys and intestine of trout and from three different adult digenetic trematodes (Deropegus sp., Crepidostomum sp., Creptotrema sp.) parasitizing the gallbladder and/or the intestine of the trout. Sequencing of PCR-amplified DNA from the 16S rRNA gene indicated that the source organism was most closely related to the sequences of E. risticii (level of sequence similarity 96.0%), the SF agent (95.9%), E. sennetsu (95.8%), and Neorickettsia helminthoeca (95.3%). The data suggest that trout and parasitic trematodes may be involved in the epidemiology of an Ehrlichia-like agent belonging to the E. sennetsu genogroup. Whether the fish agent infects Horses, dogs, or human beings, and whether it causes disease, remain to be determined.
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Infection rate of Ehrlichia risticii, the agent of Potomac Horse Fever, in freshwater stream snails (Juga yrekaensis) from northern California.
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Jeannine Berger Pusterla, Elfriede Derock, John E MadiganAbstract:Juga yrekaensis freshwater snails were tested for trematode stages and for Ehrlichia risticii DNA using a nested PCR assay. Snails were collected monthly from two Potomac Horse Fever (PHF) endemic locations in northern California (Montague and Weed). The trematode infection rate varied between 40 and 93.3% in large snails (shell size >15mm) and between 0 and 13.3% in small snails (
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infection rate of ehrlichia risticii the agent of Potomac Horse Fever in freshwater stream snails juga yrekaensis from northern california
Veterinary Parasitology, 2000Co-Authors: Nicola Pusterla, Joon-seok Chae, Eileen Johnson, Jeannine Berger Pusterla, Elfriede Derock, John E MadiganAbstract:Juga yrekaensis freshwater snails were tested for trematode stages and for Ehrlichia risticii DNA using a nested PCR assay. Snails were collected monthly from two Potomac Horse Fever (PHF) endemic locations in northern California (Montague and Weed). The trematode infection rate varied between 40 and 93.3% in large snails (shell size >15mm) and between 0 and 13.3% in small snails (<15mm). The highest trematode infection rate for large and small snails was recorded in September and the lowest infection rate for large snails was recorded in June (Weed) and October (Montague). The E. risticii PCR infection rate among small snails from both sites was similar and varied monthly between 0 and 3.3%. The PCR infection rate for large snails from Weed was high in May (20.0%) and decreased progressively until November (10.0%). The PCR infection rate for large snails from Montague was 5.0% in May, 26.3% in August and 16. 7% in October. PCR-positive snails were always related to the microscopic detection of trematode stages (virgulate cercariae). This study provides evidence that J. yrekaensis are infected with trematode cercariae that harbor E. risticii. The number of snails harboring trematode stages and the number of PCR positive snails varied with the size of the snails, the month of collection, and the geographic origin.
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Infection of Aquatic Insects with Trematode Metacercariae Carrying Ehrlichia risticii, the Cause of Potomac Horse Fever
Journal of Medical Entomology, 2000Co-Authors: Joon-seok Chae, Nicola Pusterla, Eileen Johnson, Elfriede Derock, Sharon P. Lawler, John E MadiganAbstract:We provide evidence of Ehrlichia risticii Holland, the agent of Potomac Horse Fever, in trematode stages found in aquatic insects collected from a pasture stream in northern California, using nested polymerase chain reaction (PCR) amplification and sequence analyses of the 16S rRNA, 51 kDa major antigen and groEL heat shock protein genes. E. risticii was detected in metacercariae found in the immatures and adults of the following insects: caddisflies (Trichoptera), mayflies (Ephemeroptera), damselflies (Odonata, Zygoptera), dragonflies (Odonata, Anisoptera), and stoneflies (Plecoptera). The prevalence of E. risticii was 31.9% (n = 454 individuals) in aquatic insects (13 of 17 species were positive). Prevalence within orders was as follows: 43.5% (n = 207) in caddisflies, 15.2% (n = 92) in mayflies, 13.9% (n = 115) in damselflies, 10.0% (n = 10) in dragonflies, and 80.0% (n = 30) in stoneflies. This study demonstrates a broad intermediate host range for trematodes that act as vector for E. risticii. Insects are likely to play an important role in the epidemiology of this disease.