Experimental transmission of Ehrlichia equi to horses through naturally infected ticks (Ixodes pacificus) from Northern California.
Abstract: We report the experimental transmission of Ehrlichia equi from naturally infected Ixodes pacificus ticks to horses. Three weeks after exposure to ticks, two of three horses developed clinical signs compatible with E. equi infection, while one horse remained asymptomatic. 16S rRNA gene PCR of blood leukocyte lysates was positive for all horses at various time points; two horses seroconverted. The 16S rRNA gene sequences amplified from tick-exposed horses showed more than 99% homology to corresponding fragments of the 16S rRNA genes of E. equi, Ehrlichia phagocytophila, and the human granulocytic ehrlichiosis agent.
Publication Date: 1998-07-03 PubMed ID: 9650983PubMed Central: PMC105004DOI: 10.1128/JCM.36.7.2131-2134.1998Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This study reveals the successful experimental transmission of a disease-causing bacteria, Ehrlichia equi, from ticks to horses, with evidence supported by molecular gene tests and the manifestation of clinical symptoms.
Methodology
In this experiment, naturally infected Ixodes pacificus ticks were used as carriers of the Ehrlichia equi bacteria, a pathogen that typically infects horses. They were used to determine if they could transmit the disease to horses. The researchers chose three horses for their study and exposed them to the infected ticks.
Observations Post Exposure
- Three weeks after being exposed to the ticks, two of the three horses developed clinical symptoms congruous with an E. equi infection. The symptoms observed are not specified in the abstract, but the disease is typically active in the animal’s blood.
- The third horse did not show any visible signs of disease, implying that it could be asymptomatic or the disease did not successfully transmit.
Confirmation of Infection
- The researchers used a type of molecular test, 16S rRNA gene PCR, to confirm the presence of E. equi in all three horses. They tested blood leukocyte lysates, which had been broken down to release their contents. These contents were then used as templates for the PCR test.
- PCR tests of this kind are often used to amplify and then identify specific sequences of DNA, enabling researchers to confirm the presence and identity of certain pathogens.
- All three horses tested positive at various time points, indicating that the infection had indeed been transmitted.
- Additionally, two of the horses underwent seroconversion – the process of developing detectable antibodies in the blood as a response to infection. This served as another form of confirmation that infection had occurred.
Gene Sequence Analysis
- The 16S rRNA gene sequences derived from the horses were compared with corresponding sequences in the E. equi strain, the Ehrlichia phagocytophila and the human granulocytic ehrlichiosis agent.
- The researchers discovered that the sequences extracted from the horses after exposure to the ticks showed a very high degree of similarity (more than 99% homology) to the comparison strains.
- This further confirmed the successful transmission of Ehrlichia equi from ticks to the horses.
Cite This Article
APA
Reubel GH, Kimsey RB, Barlough JE, Madigan JE.
(1998).
Experimental transmission of Ehrlichia equi to horses through naturally infected ticks (Ixodes pacificus) from Northern California.
J Clin Microbiol, 36(7), 2131-2134.
https://doi.org/10.1128/JCM.36.7.2131-2134.1998 Publication
Researcher Affiliations
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616, USA. ghreubel@mailbox.uq.edu.au
MeSH Terms
- Animals
- California
- DNA, Bacterial / analysis
- Ehrlichia / genetics
- Ehrlichia / isolation & purification
- Ehrlichiosis / transmission
- Ehrlichiosis / veterinary
- Horse Diseases / microbiology
- Horse Diseases / transmission
- Horses
- Ixodes / microbiology
- Polymerase Chain Reaction / methods
- RNA, Ribosomal, 16S / genetics
- rRNA Operon
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Citations
This article has been cited 17 times.- McVicar M, Rivera I, Reyes JB, Gulia-Nuss M. Ecology of Ixodes pacificus Ticks and Associated Pathogens in the Western United States.. Pathogens 2022 Jan 13;11(1).
- Teodorowski O, Kalinowski M, Winiarczyk D, Janecki R, Winiarczyk S, Adaszek Ł. Molecular surveillance of tick-borne diseases affecting horses in Poland-Own observations.. Vet Med Sci 2021 Jul;7(4):1159-1165.
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