Detection of Neorickettsia risticii in antemortem fecal and postmortem fetal samples, with genomic insights from complete genome sequencing of a strain recovered from an aborted equine fetus.
Abstract: Neorickettsia risticii (N. risticii) is an obligatory intracellular bacterium that causes Potomac horse fever (PHF), a disease clinically characterized by diarrhea, pyrexia, and laminitis in horses. Although sporadic reports of N. risticii infection have been linked to abortion in mares, a detailed retrospective study, including genomic analysis of the pathogen from an aborted fetus, has not been published. This study examined 546 fecal samples from clinically ill horses (January 1, 2017-December 31, 2024) and 833 colon samples from aborted equine fetuses (September 20, 2018-December 31, 2024). Using real-time PCR, N. risticii was detected in 11.5 % of fecal samples and 1.08 % of fetal colon samples. Positive antemortem cases were detected between May and September, while fetal cases occurred from September to December. The fetuses were 5-8 months of gestational age, all showing microscopic evidence of colitis. A shotgun metagenomic approach was applied directly to an archived fetal colon sample using the MiSeq platform, yielding a complete genome of N. risticii (strain KY18-EqFetus) with 99.72 % nucleotide identity to the N. risticii strain Illinois reference genome. The genome was 879,923 bp with a GC content of 41.3 %, and 2024 variants (including indels and nucleotide polymorphisms) were identified. Notably, three genes coding for small hypothetical proteins present in the reference strain were absent in KY18-EqFetus. This study provides a comprehensive investigation of N. risticii in both antemortem and postmortem equine samples and reports the first complete genome assembly of the pathogen directly from an aborted equine.
Copyright © 2025 Elsevier B.V. All rights reserved.
Publication Date: 2025-09-02 PubMed ID: 40913922DOI: 10.1016/j.vetmic.2025.110705Google Scholar: Lookup
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- Journal Article
Cite This Article
APA
Uprety T, Durazo J, Paul L, Metiner K, Ruby R, Loynachan A, Janes J, Kenndy L, Cassone L, Molly E, Quick M, Morgan J, Beyhan S, Erol E.
(2025).
Detection of Neorickettsia risticii in antemortem fecal and postmortem fetal samples, with genomic insights from complete genome sequencing of a strain recovered from an aborted equine fetus.
Vet Microbiol, 310, 110705.
https://doi.org/10.1016/j.vetmic.2025.110705 Publication
Researcher Affiliations
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America. Electronic address: Tirth.Uprety@uky.edu.
- J. Craig Venter Institute, Department of Infectious Diseases, La Jolla, CA, United States of America.
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America.
- Istanbul University-Cerrahpasa, Faculty of Veterinary Medicine, Istanbul, Turkey.
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America.
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America.
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America.
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America.
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America.
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America.
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America.
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America.
- J. Craig Venter Institute, Department of Infectious Diseases, La Jolla, CA, United States of America; University of California, San Diego, Department of Medicine, La Jolla, CA, United States of America.
- University of Kentucky Veterinary Diagnostic Laboratory, Lexington, KY 40511, United States of America. Electronic address: Erdal.Erol@uky.edu.
MeSH Terms
- Animals
- Horses
- Horse Diseases / microbiology
- Feces / microbiology
- Aborted Fetus / microbiology
- Female
- Whole Genome Sequencing / veterinary
- Pregnancy
- Genome, Bacterial
- Neorickettsia risticii / genetics
- Neorickettsia risticii / isolation & purification
- Anaplasmataceae Infections / veterinary
- Anaplasmataceae Infections / microbiology
- Fetus / microbiology
- Retrospective Studies
Conflict of Interest Statement
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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