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Evaluation of the immune status of horses with and without equine keratoconjunctivitis in particular consideration of an EHV-2 infection<br><br
Objective: EHV-2 is widespread in the horse population. Its rote as a pathogen is controversial, but its involvement in infections of the respiratory tract as well as in different forms of keratoconjunctivitis has been documented several times. Recent findings, which were based an optimised sampling techniques and the sensitive PCR method, however, showed a high percentage of EHV-2 positive swabs within the healthy horse population. Since serological data are of no significance for the diagnosis of equine keratoconjunctivitis we searched for another suitable diagnostic parameter. Material and methods: Because of EHV-2 being latent in B-cells and its possible immunosuppressive effective investigated blood samples of horses with and without ocular disease by PCR and additionally measured the relative percentages of B- and T-cells in the peripheral blood by means of flow cytometry. A total of 10 EHV-2 positive horses in which we determined the virus by PCR in PBL or ocular swabs were classified in the test group and 21 EHV-2 negative horses without virus detection were used as controls. Both groups comprised horses with and without ocular disease. Results: Regarding their T-cells there was no significant difference between horses with and without ocular disease in the test and control group. In contrast, Tour of the six healthy EHV-2 positive horses had decreased B-cell numbers. No significant difference in respect to frequency of increased B-cell numbers was observed between the four groups. Conclusion: Test animals without ocular disease had significantly more often decreased B-cell numbers than control horses with and without ocular disease, respectively. Because of the small Sample number, the results should be regarded only as first indication for a possible influence of an EHV-2 infection an the immune status. Clinical relevance: Further studies will have to clarity if the determination of the immune status by flow cytometry represents a helpful diagnostic and probably prognostic parameter for EHV-2 induced equine keratoconjunctivitis cases.