Acta Parasitologica

, Volume 57, Issue 3, pp 285–292 | Cite as

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

  • Vasyl V. Tkach
  • Jay A. Schroeder
  • Stephen E. Greiman
  • Jefferson A. Vaughan
Original Paper


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.


Neorickettsia Anaplasmataceae 16S rRNA new genotypes phylogeny Digenea circulation host associations 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Barlough J.E., Rikihisa Y., Madigan J.E. 1997. Nested polymerase chain reaction for detection of Ehrlichia risticii genomic DNA in infected horses. Veterinary Parasitology, 68, 367–373. DOI: 10.1016/S0304-4017(96)01083-7.PubMedCrossRefGoogle Scholar
  2. Barlough J.E., Reubel G.H., Madigan J.E., Vredevoe L.K., Miller P.E., Rikihisa Y. 1998. Detection of Ehrlichia risticii, the agent of Potomac horse fever, in freshwater stream snails Pleuroceridae Juga spp. of Northern California. Journal of Applied and Environmental Microbiology, 64, 2888–2893. DOI: 10.1016/S0304-4017(00)00309-5.Google Scholar
  3. Chaichanasiriwithaya W., Rikihisa Y., Yamamoto S., Reed S.M., Perryman L.E., Crawford T.B., Palmer G. 1994. Antigenic, morphologic, and molecular characterization of 9 new Ehrlichia risticii isolates. Journal of Clinical Microbiology, 38, 3026–3033.Google Scholar
  4. Dutta S.K., Vemulapalli R., Biswas B. 1998. Association of deficiency in antibody response to vaccine and heterogeneity of Ehrlichia risticii strains with Potomac horse fever vaccine failure in horses. Journal of Clinical Microbiology, 36, 506–512.PubMedGoogle Scholar
  5. Farrell R.K., Leader R.W., Johnston S.D. 1973. Differentiation from salmon poisoning disease and Elokomin fluke disease fever: studies with the black bear (Ursus americanus). American Journal of Veterinary Research, 34, 919–922.PubMedGoogle Scholar
  6. Fukuda T., Kitao T., Keida Y. 1954. Studies on the causative agent of “Hyuganetsu” disease. I. Isolation of the agent and its inoculation trial in human beings. Medical Biology, 32, 200–209.Google Scholar
  7. Gibson K.E., Rikihisa Y., Zhang C., Martin C. 2005. Neorickettsia risticii is vertically transmitted in the trematode Acanthatrium oregonense and horizontally transmitted to bats. Environmental Microbiology, 7, 203–212. DOI: 10.1111/j.1462-2920.2004.00683.x.PubMedCrossRefGoogle Scholar
  8. Gibson K., Pastenkos G., Moesta S., Rikihisa Y. 2011. Neorickettsia risticii surface-exposed proteins: Proteomics identification, recognition by naturally-infected horses and strain variations. Veterinary Research, 42, 71. DOI: 10.1186/1297-9716-42-71.PubMedCrossRefGoogle Scholar
  9. Guindon S., Gascuel O. 2003. A simple, fast, and accurate algorithm to estimate large phylogenies by maximum likelihood. Systematic Biology, 52, 696–704. DOI: 10.1080/10635150390235520.PubMedCrossRefGoogle Scholar
  10. Hall T.A. 1999. BioEdit: a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. Nucleic Acids Symposium Series, 41, 95–98.Google Scholar
  11. Headley S.A., Scorpio D.G., Vidotto O., Dumler J.S. 2011. Neorickettsia helminthoeca and salmon poisoning disease: a review. Veterinary Journal, 187, 165–173. DOI: 10.1016/j.tvjl.2009.11.019.CrossRefGoogle Scholar
  12. Huelsenbeck J.P., Ronquist F. 2001. MRBAYES: Bayesian inference of phylogeny. Bioinformatics, 17, 754–755. DOI: 10.1093/bioinformatics/17.8.754.PubMedCrossRefGoogle Scholar
  13. Hortle K.G. 2007. Consumption and the yield of fish and other aquatic animals from the Lower Mekong Basin. In: MRC Technical Report No. 16. Vientiane: Mekong River Commission.Google Scholar
  14. Maddison D.R., Maddison W.P. 2005. MacClade 4: Analysis of phylogeny and character evolution. Version 4.08a.
  15. Madigan J.E., Pusterla N. 2000. Ehrlichial diseases. Veterinary Clinics of North America Equine Practice, 16, 487–499.Google Scholar
  16. Millemann R.E., Gebhardt G.A., Knapp S.E. 1964. “Salmon poisoning” disease. I. Infection in a dog from marine salmonids. Journal of Parasitology, 50, 588–589. DOI: 10.2307/3275629.PubMedCrossRefGoogle Scholar
  17. Misao T., Kobayashi Y. 1954. Studies on infectious mononucleosis. I. Isolation of etiologic agent from blood, bone marrow, and lymph node of a patient with infectious mononucleosis by using mice. Tokyo Iji Shinshi, 71, 683–686.Google Scholar
  18. Mulville P. 1991. Equine monocytic ehrlichiosis (Potomac horse fever): a review. Equine Veterinary Journal, 23, 400–404.PubMedCrossRefGoogle Scholar
  19. Newton P., Rolain J.M., Rasachack B., Mayxay M., Vathanatham K., Seng P., Phetsouvanh R., Thammavong T., Zahidi J., Suputtamongkol Y., Syhavong B., Raoult D. 2009. Sennetsu neorickettsiosis: a probable fish-borne cause of fever rediscovered in Laos. American Journal of Tropical Medicine and Hygiene, 81, 190–194.PubMedGoogle Scholar
  20. Palmer J.E. 1993. Potomac horse fever. Veterinary Clinics of North America: Equine Practice, 9, 399–410.PubMedGoogle Scholar
  21. Patten J.A. 1952. The Life Cycle of Conspicuum icteridorum Denton and Byrd, 1951, (Trematoda: Dicrocoeliidae). Journal of Parasitology, 38, 165–182.PubMedCrossRefGoogle Scholar
  22. Philip C.B., Hadlow W.J., Hughes L.E. 1953. Neorickettsia helmintheca, a new rickettsia-like disease agent of dogs in western United States transmitted by a helminth. 6th International Congress of Microbiology, Rome, Vol. II, 256–257.Google Scholar
  23. Philip C.B. 1955. There is always something new under the “parasitological sun” (the unique story of helminth-borne salmon poisoning disease). Journal of Parasitology, 41, 125–148.PubMedCrossRefGoogle Scholar
  24. Posada D. 2008. jModelTest: Phylogenetic Model Averaging. Molecular Biology and Evolution, 25, 1253–1256. DOI: 10.1093/molbev/msn083.PubMedCrossRefGoogle Scholar
  25. Pusterla N., Johnson E., Chae J., DeRock E., Willis M., Hedrick R.P., Madigan J.E. 2000. Molecular detection of an Ehrlichia-like agent in rainbow trout (Oncorhynchus mykiss) from Northern California. Veterinary Parasitology, 92, 199–207. DOI: Scholar
  26. Rikihisa Y. 1991. The tribe Ehrlichia and ehrlichial diseases. Clinical Microbiology Review, 4, 286–308. DOI: 10.1128/CMR.4.3.286.Google Scholar
  27. Rikihisa Y., Zhang C., Kanter M., Cheng Z., Ohashi N., Fukuda T. 2004. Analysis of p51, groESL, and the major antigen P51 in various species of Neorickettsia, an obligatory intracellular bacterium that infects trematodes and mammals. Journal of Clinical Microbiology, 42, 3823–3826. DOI: 10.1128/JCM.42.8.3823-3826.2004.PubMedCrossRefGoogle Scholar
  28. Sakawa H., Farrell R.K., Mori M. 1973. Differentiation of salmon poisoning disease and Elokomin fluke fever: complement fixation. American Journal of Veterinary Research, 34, 923–925.PubMedGoogle Scholar
  29. Seng P., Rolain J.M., Raoult D., Brouqui P. 2009. Detection of new Anaplasmataceae in the digestive tract of fish from southeast Asia. Clinical Microbiology and Infection, 15, Suppl 2, 88–90. DOI: 10.1111/j.1469-0691.2008.02252.x.PubMedCrossRefGoogle Scholar
  30. Tkach V.V., Pawlowski J. 1999. A new method of DNA extraction from the ethanol-fixed parasitic worms. Acta Parasitologica, 44, 147–148.Google Scholar
  31. Vemulapalli R., Biswas B., Dutta S.K. 1995. Pathogenic, immunologic, and molecular differences between two Ehrlichia risticii strains. Journal of Clinical Microbiology, 33, 2987–2993.PubMedGoogle Scholar
  32. Vaughan J.A., Tkach V.V., Greiman S.E. 2012. Neorickettsial endosymbionts of the Digenea: diversity, transmission and distribution. Advances in Parasitology, 79, 253–297. DOI: 10.1016/B978-0-12-398457-9.00003-2.PubMedGoogle Scholar
  33. Walker D.H., Dumler J.S. 1996. Emergence of the Ehrlichioses as human health problems. Emerging Infectious Diseases, 2, 18–29.PubMedCrossRefGoogle Scholar
  34. Yamaguti S. 1975. A Synoptic Review of Life Histories of Digenetic Trematodes of Vertebrates. Tokyo, Keigaku.Google Scholar

Copyright information

© Versita Warsaw and Springer-Verlag Wien 2012

Authors and Affiliations

  • Vasyl V. Tkach
    • 1
  • Jay A. Schroeder
    • 1
  • Stephen E. Greiman
    • 1
  • Jefferson A. Vaughan
    • 1
  1. 1.Department of BiologyUniversity of North DakotaGrand ForksUSA

Personalised recommendations