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Journal of veterinary internal medicine2009; 23(3); 636-642; doi: 10.1111/j.1939-1676.2009.0317.x

Molecular evidence for persistence of Anaplasma phagocytophilum in the absence of clinical abnormalities in horses after recovery from acute experimental infection.

Abstract: Anaplasma phagocytophilum infects several mammalian species, and can persist in sheep, dogs, and calves. However, whether this organism persists in horses or induces long-term clinical abnormalities is not known. Objective: To evaluate whether A. phagocytophilum can persist in horses and to document clinical findings for 3 months after complete recovery from acute disease. Methods: Five clinically normal adult horses that had recovered spontaneously from experimentally induced acute disease caused by a Swedish equine isolate of A. phagocytophilum. Methods: Horses were monitored for up to 129 days post inoculation (PI) by daily clinical examination and at least alternate day blood sampling for evidence of A. phagocytophilum on polymerase chain reaction (PCR) and blood smears. All horses were euthanized and underwent postmortem examination. Results: All horses were periodically PCR positive after recovery from acute infection. Before day 66 PI 2 horses were persistently PCR negative whereas 3 horses were intermittently PCR positive. Subsequently, 4 of 5 horses were intermittently PCR positive, particularly after stress mimicking interventions. One animal was positive immediately before postmortem examination. Clinical abnormalities related to persistence of anaplasma were not observed. No specific changes were found at postmortem examination, and all sampled tissues from all horses were negative on PCR for A. phagocytophilum. Conclusions: Infection with A. phagocytophilum can persist in the horse for at least 129 days. However, the continued presence of the organism is not associated with detectable clinical or pathological abnormalities.
Publication Date: 2009-08-04 PubMed ID: 19645847DOI: 10.1111/j.1939-1676.2009.0317.xGoogle Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

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The research investigated the persistence of Anaplasma phagocytophilum, a bacterium that infects mammals, in horses. It found that the infection can persist for at least 129 days without showing clinical symptoms or causing detectable pathological changes.

Objective

  • The main purpose of the study was to determine if Anaplasma phagocytophilum could persist in horses, even after they had fully recovered from the acute phase of the infection. This organism is known to persist in several other mammalian species, but there wasn’t clear evidence regarding its persistence in horses. The researchers were also keen to document any clinical findings in the three months following recovery from the acute disease.

Methodology

  • Five healthy adult horses that had spontaneously recovered from experimentally induced acute disease caused by A. phagocytophilum were chosen for the study.
  • These horses were closely monitored for a period of up to 129 days after infection. This involved daily clinical examinations and blood sampling at least every second day. The researchers tested the blood samples for A. phagocytophilum using polymerase chain reaction (PCR) and by checking blood smears. After the monitoring period, the horses were euthanized for postmortem examination.

Key Findings

  • Throughout the monitoring period, all the horses tested positive for A. phagocytophilum at certain times, showing that the infection could persist even after the acute phase of the disease.
  • In the first 66 days post infection, two horses continuously tested negative for A. phagocytophilum while the other three tested positive intermittently. After this period, four out of the five horses were intermittently testing positive, particularly following stressful interventions. One horse even tested positive immediately before being euthanized.
  • Despite the persistence of A. phagocytophilum in the horses, the researchers did not observe any clinical abnormalities associated with this. The postmortem examination also did not reveal any specific changes and all the tissues tested negative for A. phagocytophilum.

Conclusion

  • The study concluded that an A. phagocytophilum infection can persist in horses for at least 129 days. However, the persistence of the bacterium does not come with detectable clinical symptoms or pathological abnormalities.

Cite This Article

APA
Franzén P, Aspan A, Egenvall A, Gunnarsson A, Karlstam E, Pringle J. (2009). Molecular evidence for persistence of Anaplasma phagocytophilum in the absence of clinical abnormalities in horses after recovery from acute experimental infection. J Vet Intern Med, 23(3), 636-642. https://doi.org/10.1111/j.1939-1676.2009.0317.x

Publication

ISSN: 0891-6640
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 23
Issue: 3
Pages: 636-642

Researcher Affiliations

Franzén, P
  • Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden. vet.franzen.@gmail.com
Aspan, A
    Egenvall, A
      Gunnarsson, A
        Karlstam, E
          Pringle, J

            MeSH Terms

            • Anaplasma phagocytophilum / isolation & purification
            • Anaplasmosis / microbiology
            • Animals
            • Chronic Disease
            • DNA, Bacterial / isolation & purification
            • Horse Diseases / microbiology
            • Horses
            • Molecular Diagnostic Techniques

            Citations

            This article has been cited 20 times.
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