Neorickettsial Endosymbionts of the Digenea

Vaughan, Jefferson A.; Tkach, Vasyl V.; Greiman, Stephen E.

doi:10.1016/b978-0-12-398457-9.00003-2

Cited by 57 publications

(45 citation statements)

References 113 publications

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“…They are obligate intracellular endosymbionts of digeneans (Platyhelminthes, Digenea), but may also infect cells and tissues of vertebrate hosts of digeneans and are capable of causing diseases of wildlife and humans (Rikihisa 1991, Walker and Dumler 1996, Newton et al 2009, Headley et al 2011, Vaughan et al 2012. Neorickettsiae persist through all stages of digenean complex life cycles that always include an aquatic or a terrestrial mollusk as the first intermediate host and may incorporate an invertebrate or a vertebrate second intermediate host.…”

Section: Introductionmentioning

confidence: 99%

“…Diseases caused by neorickettsiae in vertebrates can be severe (e.g., Sennetsu fever in humans) or even fatal (e.g., salmon dog poisoning, Potomac horse fever). Detailed accounts of the history of discovery and pathogenicity of Neorickettsia can be found in several published reviews (Mulville 1991, Rikihisa 1991, Palmer 1993, Rikihisa et al 2004, Headley et al 2011, Vaughan et al 2012.…”

Section: Introductionmentioning

confidence: 99%

“…As discussed by Vaughan et al (2012) the validity of some of these records is doubtful because of potential previous exposure to vaccines and trade/relocation histories. Records resulting from PCR detection of neorickettsial DNA *Corresponding author: vasyl.tkach@email.und.edu Vasyl V. Tkach et al 286 are known from North and South America and Asia.…”

Section: Introductionmentioning

confidence: 99%

“…However, even those records are mostly based on Neorickettsia found in vertebrate hosts (horses, dogs, humans, fish), but very rarely from digeneans. Only 14-15 digenean species, in most cases identified only to genus or family level, have been previously confirmed as hosts of Neorickettsia (Vaughan et al 2012).…”

Section: Introductionmentioning

confidence: 99%

“…These infections were invariably connected to lotic habitats and to digeneans having either terrestrial/ aquatic (N. helminthoeca, N. risticii, EFF agent) or fully aquatic (Rainbow trout agent) life cycles. Only 7 digenean species were reported as hosts of Neorickettsia in the United States (Philip et al 1953;Farrell et al 1973;Pusterla et al 2000Pusterla et al , 2003Gibson et al 2005;Vaughan et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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New genetic lineages, host associations and circulation pathways of Neorickettsia endosymbionts of digeneans

Tkach

Schroeder

Greiman

et al. 2012

Acta Parasitologica

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Neorickettsia is a genus of intracellular bacteria endosymbiotic in digeneans that may also invade cells of vertebrates and are known to cause diseases of wildlife and humans. Herein, we report results of screening for Neorickettsia of an extensive collection of DNA extracts from adult and larval digeneans obtained from various vertebrates and mollusks in the United States. Seven isolates of Neorickettsia were detected by PCR and sequenced targeting a 527 bp long region of 16S rRNA. Sequence comparison and phylogenetic analysis demonstrated that four isolates matched published sequences of Neorickettsia risticii. Three other isolates, provisionally named "catfish agents 1 and 2" (obtained from Megalogonia ictaluri and Phyllodistomum lacustri, both parasitic in catfishes) and Neorickettsia sp. (obtained from cercariae of Diplostomum sp.), differed from previously known genotypes of Neorickettsia and are likely candidates for new species. All 7 isolates of Neorickettsia were obtained from digenean species and genera that were not previously reported as hosts of these bacteria. Members of four digenean families (Dicrocoeliidae, Heronimidae, Macroderoididae and Gorgoderidae) are reported as hosts of Neorickettsia for the first time. Our study reveals several new pathways of Neorickettsia circulation in nature. We have found for the first time a Neorickettsia from a digenean (dicrocoeliid Conspicuum icteridorum) with an entirely terrestrial life cycle. We found N. risticii in digeneans (Alloglossidium corti and Heronimus mollis) with entirely aquatic life cycles. Previously, this Neorickettsia species was known only from digeneans with aquatic/terrestrial life cycles. Our results suggest that our current knowledge of the diversity, host associations and circulation of neorickettsiae is far from satisfactory.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

New genetic lineages, host associations and circulation pathways of Neorickettsia endosymbionts of digeneans

Tkach

Schroeder

Greiman

et al. 2012

Acta Parasitologica

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A fine‐scale phylogenetic assessment of digenean trematodes in central Alberta reveals we have yet to uncover their total diversity

Gordy

Hanington

2019

Ecology and Evolution

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Despite over 100 years of digenean trematode parasite species descriptions, from a wide diversity of vertebrate and invertebrate host species, our ability to recognize the diversity of trematode species within a single lake remains an incredible challenge. The most challenging aspect is the identification of species from larval stages derived from intermediate hosts, due to the disjointed data of adult worm morphological descriptions, from which species are named, and links to corresponding molecular identifiers in depauperate databases. Cryptic species also play a significant role in the challenge of linking trematode larvae to adults, species identifications, and estimating diversity. Herein, we utilize a large, longitudinal dataset of snail first‐intermediate host infection data from lakes in Alberta, Canada, to infer trematode larval diversity using molecular phylogenetics and snail host associations. From our assessments, we uncover a diversity of 79 larval trematode species among just five snail host species. Only 14 species were identified to a previously described species, while the other 65 species are either cryptic or otherwise unrepresented by mitochondrial genes in GenBank. This study currently represents the largest and most diverse singular molecular survey of trematode larval fauna composed of over one thousand mitochondrial sequences. Surprisingly, rarefaction analyses indicate we have yet to capture the complete diversity of trematodes from our sampling area.

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Salmon poisoning disease in grizzly bears with population recovery implications

et al. 2018

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Wildlife restoration programs depend on having animals that have evolved to handle the constraints, including disease, posed by the new environment. Grizzly bears (Ursus arctos horribilis) once thrived while feeding on salmon (Onchorhynchus spp.) and other foods in California, Oregon, Washington, and Idaho, USA. Unlike Canadian and Alaskan salmon, salmon in lower latitudes often carry an encysted fluke (Nanophyetus salmincola) containing an endosymbiont (Neorickettsia spp.) that can produce a deadly disease in ursids and canids called salmon poisoning disease (SPD). Current recovery plans for grizzly bears in the North Cascades of Washington and the mountains of central Idaho, where infected salmon currently occur, call for using bears from several interior populations. We hypothesized that such bears with no history of salmon consumption will be sensitive to SPD. To test that idea, we fed a limited amount of fresh Chinook salmon (O. tshawytscha) harvested from rivers draining the east and west sides of the Cascades to 11 captive grizzly bears in which both parents were from populations with no history of SPD. We detected N. salmincola ova in the feces, and 8 bears exhibited typical SPD symptoms, which included decreased or no appetite, lethargy, vomiting, and diarrhea. We identified N. helminthoeca and Stellantchasmus falcatus (SF) agent (Neorickettsia sp.) in the salmon, but only SF agent occurred in the sick bears. Stellantchasmus falcatus agent is a relatively new arrival in the Pacific Northwest. Because of the severity of the disease and the potential for mortality without treatment, additional studies should be conducted to determine the distribution and prevalence of SF agent in salmon and kokanee (O. nerka) in the recovery area, develop a serum antibody test that could be used to determine exposure of bears to SF agent, and use that test to determine if grizzly bears or American black bears (U. americanus) currently living in the Pacific Northwest have been infected and recovered. If either of the latter have occurred, SPD may not prevent the successful restoration of grizzly bears where SF agent‐infected salmon will be consumed. © 2018 The Wildlife Society.

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Neorickettsial Endosymbionts of the Digenea

Cited by 57 publications

References 113 publications

New genetic lineages, host associations and circulation pathways of Neorickettsia endosymbionts of digeneans

New genetic lineages, host associations and circulation pathways of Neorickettsia endosymbionts of digeneans

A fine‐scale phylogenetic assessment of digenean trematodes in central Alberta reveals we have yet to uncover their total diversity

Salmon poisoning disease in grizzly bears with population recovery implications

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