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Transmission of Anaplasma phagocytophila (human granulocytic ehrlichiosis agent) in horses using experimentally infected ticks (Ixodes scapularis).
Abstract: Most human granulocytic ehrlichiosis (HGE) studies carried out in horses use needle inoculation of infected leucocytes or cell cultures. This route of inoculation does not accurately reflect natural infection of the tick-borne agent. To investigate whether tick transmission influences the course of granulocytic ehrlichiosis in the horse model, experimental transmission through infected laboratory-reared Ixodes scapularis ticks was attempted into two healthy horses. One additional horse served as negative control and was exposed to uninfected ticks. Eleven days after exposure to nymphal or adult ticks infected with Anaplasma phagocytophila (HGE agent) the two horses developed severe clinical and laboratory signs consistent with granulocytic ehrlichiosis. Bacteraemia was determined at various time points in the two horses by observation of morulae within neutrophils and by detection of A. phagocytophila genomic DNA by PCR of peripheral blood leucocytes. Further, both horses seroconverted. In contrast the control horse stayed uninfected. The results demonstrate that A. phagocytophila can be experimentally transmitted by infected nymphal and adult ticks and that the agent is able to produce a severe disease, similar to naturally occurring cases. Therefore, tick transmission is highly reproducible and can be successfully used in the equine animal model in order to study HGE.
Publication Date: 2002-12-18 PubMed ID: 12485358DOI: 10.1046/j.1439-0450.2002.00598.xGoogle Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
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.
The research article discusses how the transmission of Anaplasma phagocytophila, the causative bacteria of human granulocytic ehrlichiosis (HGE), can be studied in horses through the use of lab-reared ticks. The findings reveal that tick transmission of the bacteria can produce severe illness in horses, similar to natural cases, making it a useful approach to study HGE.
Methodology
- The researchers performed their experimental study on two healthy horses which served as the subjects for their investigations while an additional horse served as a negative control.
- These horses were exposed to lab-reared ticks, Ixodes scapularis, which were infected with Anaplasma phagocytophila. The control horse, in contrast, was exposed to uninfected ticks.
Findings
- The outcome showed that eleven days post exposure to the infected nymphal or adult ticks, the two study horses displayed severe symptoms and lab signs consistent with granulocytic ehrlichiosis.
- Further evidence of the infection was obtained through examination of their blood samples. The researchers found A. phagocytophila genomic DNA through PCR of peripheral blood leukocytes. Morulae within neutrophils was also observed, further confirming the presence of an infection.
- Both horses also showed seroconversion, a clear indication of an immune response to the infection.
- The control horse, on the other hand, remained uninfected.
Conclusion
- The results from this study provide clear evidence that tick transmission of A. phagocytophila produces a severe disease identical to naturally occurring cases in horses.
- This finding will be beneficial in future research as it provides a reliable, reproducible method through which tick transmission of A. phagocytophila can be studied.
- This equine model can henceforth be utilized to gain deeper understanding about the ecology and pathogenicity of HGE.
Cite This Article
APA
Pusterla N, Chae JS, Kimsey RB, Berger Pusterla J, DeRock E, Dumler JS, Madigan JE.
(2002).
Transmission of Anaplasma phagocytophila (human granulocytic ehrlichiosis agent) in horses using experimentally infected ticks (Ixodes scapularis).
J Vet Med B Infect Dis Vet Public Health, 49(10), 484-488.
https://doi.org/10.1046/j.1439-0450.2002.00598.x Publication
Researcher Affiliations
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA. npusterla@ucdavis.edu
MeSH Terms
- Anaplasma phagocytophilum / genetics
- Anaplasma phagocytophilum / pathogenicity
- Animals
- DNA, Bacterial / genetics
- DNA, Bacterial / isolation & purification
- Ehrlichiosis / transmission
- Ehrlichiosis / veterinary
- Female
- Horse Diseases / microbiology
- Horse Diseases / pathology
- Horse Diseases / transmission
- Horses
- Humans
- Ixodes / microbiology
- Male
- Polymerase Chain Reaction / veterinary
Grant Funding
- AI14213 / NIAID NIH HHS
Citations
This article has been cited 12 times.- Namjoshi P, Dahmani M, Sultana H, Neelakanta G. Rickettsial pathogen inhibits tick cell death through tryptophan metabolite mediated activation of p38 MAP kinase. iScience 2023 Jan 20;26(1):105730.
- Campos JBV, Martins FS, de Oliveira CE, Taveira AA, Oliveira JR, Gonçalves LR, Cordeiro MD, Calchi AC, de Campos Binder L, Serpa MCA, Barbieri ARM, Labruna MB, Machado RZ, de Andrade GB, André MR, Herrera HM. Tick-borne zoonotic agents infecting horses from an urban area in Midwestern Brazil: epidemiological and hematological features. Trop Anim Health Prod 2021 Sep 22;53(5):475.
- Sundstrom KD, Lineberry MW, Grant AN, Duncan KT, Ientile MM, Little SE. Equine attachment site preferences and seasonality of common North American ticks: Amblyomma americanum, Dermacentor albipictus, and Ixodes scapularis. Parasit Vectors 2021 Aug 14;14(1):404.
- Taank V, Dutta S, Dasgupta A, Steeves TK, Fish D, Anderson JF, Sultana H, Neelakanta G. Human rickettsial pathogen modulates arthropod organic anion transporting polypeptide and tryptophan pathway for its survival in ticks. Sci Rep 2017 Oct 16;7(1):13256.
- Davies RS, Madigan JE, Hodzic E, Borjesson DL, Dumler JS. Dexamethasone-induced cytokine changes associated with diminished disease severity in horses infected with Anaplasma phagocytophilum. Clin Vaccine Immunol 2011 Nov;18(11):1962-8.
- Tate CM, Mead DG, Luttrell MP, Howerth EW, Dugan VG, Munderloh UG, Davidson WR. Experimental infection of white-tailed deer with Anaplasma phagocytophilum, etiologic agent of human granulocytic anaplasmosis. J Clin Microbiol 2005 Aug;43(8):3595-601.
- Mahesh PP, Sultana H, Neelakanta G. An arthropod transporter IsOATP4056 exerts inhibitory effect on its interacting membrane protein to facilitate rickettsial pathogen survival in ticks. Cell Commun Signal 2025 Nov 22;23(1):540.
- Mahesh PP, Kolape J, Sultana H, Neelakanta G. McFarland Standards-Based Spectrophotometry Method for Calculating Approximate Multiplicity of Infection for an Obligate Intracellular Bacterium Anaplasma phagocytophilum. Microorganisms 2025 Mar 14;13(3).
- Namjoshi P, Kolape J, Patel A, Sultana H, Neelakanta G. Rickettsial pathogen augments tick vesicular-associated membrane proteins for infection and survival in the vector host. mBio 2025 Mar 12;16(3):e0354924.
- Bogdan AM, Mitrea IL, Ionita M. Equine Granulocytic Anaplasmosis: A Systematic Review and Meta-Analysis on Clinico-Pathological Findings, Diagnosis, and Therapeutic Management. Vet Sci 2024 Jun 13;11(6).
- Aleman M, Vedavally U, Pusterla N, Wensley F, Berryhill E, Madigan JE. Common and atypical presentations of Anaplasma phagocytophilum infection in equids with emphasis on neurologic and muscle disease. J Vet Intern Med 2024 Jan-Feb;38(1):440-448.
- Pusterla N, Leutenegger CM, Chae JS, Lutz H, Kimsey RB, Dumler JS, Madigan JE. Quantitative evaluation of ehrlichial burden in horses after experimental transmission of human granulocytic Ehrlichia agent by intravenous inoculation with infected leukocytes and by infected ticks. J Clin Microbiol 1999 Dec;37(12):4042-4.
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