Acute clinical, hematologic, serologic, and polymerase chain reaction findings in horses experimentally infected with a European strain of Anaplasma phagocytophilum.
Abstract: Six horses were experimentally infected by administration of horse blood containing a Swedish strain of Anaplasma phagocytophilum. The polymerase chain reaction (PCR) signal was consistently detected 2-3 days before appearance of clinical signs and persisted 4-9 days beyond abatement of clinical signs, whereas diagnostic inclusion bodies were 1st noted on average 2.6 +/- 1.5 (SD) days after onset of fever. Clinical signs and hematologic changes were largely indistinguishable from those previously reported for diseases caused by A phagocytophilum (formerly Ehrlichia equi--"Californian agent") and the human-derived human granulocytic ehrlichiosis agent. Horses 1st demonstrated antibody response 12-16 days after inoculation, 2 cases of which were still febrile, and serotiters rapidly peaked within 3-7 days of clinical illness. One horse died during the acute stage of disease, but initial clinical signs and hematologic changes were similar to those of other infected horses. This report shows that, despite minor genetic differences, a European equine-derived strain of A. phagocytophilum may be similar in pathogenicity to the Californian agent. The PCR used holds promise to widen the diagnostic window and would also be diagnostic during the initial days of clinical disease when inclusions in neutrophils in blood smears are not yet apparent.
Publication Date: 2005-04-13 PubMed ID: 15822569DOI: 10.1892/0891-6640(2005)192.0.co;2Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research article details an experiment where six horses were intentionally infected with a Swedish strain of Anaplasma phagocytophilum, studying the resultant clinical, hematological, serological, and molecular effects. The study found that despite minor genetic differences, the European strain proved similar to a Californian strain, with Polymerase chain reactions (PCR) providing considerable promise for early diagnosis.
Experimental Procedure and Findings
- The research commenced with six horses being experimentally infected with a Swedish variant of Anaplasma phagocytophilum, administered through horse blood.
- The team discovered that the PCR signal – a primary indicator of the presence of infection – could be consistently perceived between two and three days before any external clinical signs became visible. They also noted that this signal continued for four to nine days after the medical symptoms had subsided.
- Inclusions, which are structures formed inside the cell after infections, first emerged an average of 2.6 days after the fever kicked in.
Comparison with Other Findings
- The clinical signs and hematologic changes observed in the horses closely resembled those previously reported for diseases caused by A. phagocytophilum and other human-derived agents.
- These signs and changes were indistinguishable, suggesting an overall similarity between the European strain and others, despite minor genetic differences.
- There was an initial delay in antibody response, which was noted 12-16 days after inoculation, peaking rapidly within 3-7 days of clinical illness.
Conclusions and Implications
- Although one horse did die during the acute stage of the disease, its initial clinical signs and hematologic changes did not differ from the other horses, further supporting the consistent nature of the infection.
- The researchers concluded that the European equine-derived strain of A. phagocytophilum might be almost as pathogenic as the Californian agent.
- Significantly, the team expressed confidence in the PCR testing ability to enlarge the diagnostic window, enabling diagnosis during the early days when inclusions are not yet visible in blood smears.
Cite This Article
APA
Franzén P, Aspan A, Egenvall A, Gunnarsson A, Aberg L, Pringle J.
(2005).
Acute clinical, hematologic, serologic, and polymerase chain reaction findings in horses experimentally infected with a European strain of Anaplasma phagocytophilum.
J Vet Intern Med, 19(2), 232-239.
https://doi.org/10.1892/0891-6640(2005)192.0.co;2 Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden. peter.franzen@nshorse.se
MeSH Terms
- Anaplasma phagocytophilum / immunology
- Anaplasma phagocytophilum / isolation & purification
- Animals
- Antibodies, Bacterial / blood
- Blood Cell Count / veterinary
- Body Temperature
- Ehrlichiosis / blood
- Ehrlichiosis / immunology
- Ehrlichiosis / physiopathology
- Ehrlichiosis / veterinary
- Horse Diseases / blood
- Horse Diseases / immunology
- Horse Diseases / physiopathology
- Horses
- Polymerase Chain Reaction / veterinary
Citations
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