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Home / Equine Research Bank / J Clin Microbiol / Isolation of the equine granulocytic ehrlichiosis agent, Ehr...
Journal of clinical microbiology1996; 34(3); 664-670; doi: 10.1128/jcm.34.3.664-670.1996

Isolation of the equine granulocytic ehrlichiosis agent, Ehrlichia equi, in tick cell culture.

Abstract: The equine granulocytic ehrlichiosis agent, Ehrlichia equi, is closely related or identical to the human granulocytic ehrlichiosis (HGE) agent. Both are suspected of being transmitted by ticks. We have successfully isolated E. equi in a cell line, IDE8, derived from a putative vector, the tick Ixodes scapularis. Peripheral blood leukocytes from an experimentally infected horse were inoculated onto IDE8 monolayers. Cultures were incubated in a candle jar at 34 degrees C in tick cell culture medium with NaHCO3 and an organic buffer [3-(N-morpholino)-propanesulfonic acid] (MOPS). Within 2 weeks, infected cells were detected in Giemsa-stained culture samples, and the organisms subsequently spread to uninfected cells in the cultures. E. equi was passaged serially by transferring a portion of an infected culture to new cell layers every 2 to 3 weeks. The identity of the organisms was confirmed by PCR using oligonucleotide primers specific for E. equi and the HGE agent and by immunocytology. Homologous equine antibodies and human anti-HGE convalescent serum recognized E. equi grown in tick cell culture. Electron microscopy revealed electron-lucent and -dense ehrlichia-like forms developing within host cell endosomes. E. equi passaged twice in tick cell culture retained infectivity and pathogenicity for the equine host, as demonstrated by intravenous inoculation of a suspension of infected tick cells and subsequent reisolation from peripheral blood, in fulfillment of Koch's postulates. The horse developed severe clinical signs, i.e., fever, inappetence, thrombocytopenia, icterus, and limb edema, typical of granulocytic equine ehrlichiosis, within 1 week.
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Publication Date: 1996-03-01 PubMed ID: 8904434PubMed Central: PMC228866DOI: 10.1128/jcm.34.3.664-670.1996Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research successfully cultured Ehrlichia equi, the cause of equine granulocytic ehrlichiosis, in tick cell lines, confirming its tick-borne nature and retaining its infectivity to horses.

Overview of the Research

  • Ehrlichia equi is the causative agent of equine granulocytic ehrlichiosis, a disease that causes severe illness in horses. This organism is suspected to be transmitted by ticks.
  • This research successfully managed to grow E. equi in a cell culture derived from the presumed tick vector, Ixodes scapularis. Characteristic symptoms of the disease were successfully reproduced by inoculating horses with these cultured cells.

Methodology

  • The researchers used blood leukocytes from a horse that had been intentionally infected with E. equi. Leukocytes are a type of blood cell that is known to be a target for E. equi infection. This blood sample was inoculated onto cultures of the IDE8 cell line, derived from the tick Ixodes scapularis, presumed to be the vector of this disease.
  • The culture was incubated with substances known to be conducive for the growth of tick cells. Within two weeks, E. equi was found to have infected cells in the cultures, as detected via staining and microscopic observation. The organism was also found to spread to uninfected cells in the culture.

Results

  • E. equi was successfully grown in tick cell cultures. It was confirmed to be E. equi via analysis of its genetic material with polymerase chain reaction (PCR) and via its reaction with specific antibodies.
  • Electron microscopy, a method of observing structures at a very fine level, revealed the typical forms of Ehrlichia organisms within infected cells.
  • Moreover, E. equi cultured in this way was found to retain its ability to infect and cause disease in horses. This was confirmed by inoculating a horse with the cultured cells and observing the typical symptoms of equine granulocytic ehrlichiosis, such as fever, lack of appetite, low platelet count, yellowing of the skin and membrane (icterus), and swelling of limbs (edema).

Conclusions

  • The results of this research confirm the tick-borne nature of E. equi and its role in causing equine granulocytic ehrlichiosis.
  • The successful culture of E. equi in tick cell lines and its infectivity to horses means this could serve as a reliable model for future research into this organism and the disease it causes.

Cite This Article

APA
Munderloh UG, Madigan JE, Dumler JS, Goodman JL, Hayes SF, Barlough JE, Nelson CM, Kurtti TJ. (1996). Isolation of the equine granulocytic ehrlichiosis agent, Ehrlichia equi, in tick cell culture. J Clin Microbiol, 34(3), 664-670. https://doi.org/10.1128/jcm.34.3.664-670.1996

Publication

Journal of clinical microbiology
ISSN: 0095-1137
NlmUniqueID: 7505564
Country: United States
Language: English
Volume: 34
Issue: 3
Pages: 664-670

Researcher Affiliations

Munderloh, U G
  • Department of Entomology, University of Minnesota, St. Paul 55108, USA. munde001@maroon.tc.umn.edu
Madigan, J E
    Dumler, J S
      Goodman, J L
        Hayes, S F
          Barlough, J E
            Nelson, C M
              Kurtti, T J

                MeSH Terms

                • Animals
                • Base Sequence
                • Cells, Cultured
                • Ehrlichia / growth & development
                • Ehrlichia / isolation & purification
                • Ehrlichiosis / veterinary
                • Horse Diseases / microbiology
                • Horses
                • Ixodes / microbiology
                • Molecular Sequence Data

                Grant Funding

                • AI37772 / NIAID NIH HHS
                • AR37909 / NIAMS NIH HHS

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