Molecular identification of Ehrlichia ewingii infection in dogs: 15 Cases (1997-2001)

Abstract

Objective - To determine historical, physical examination, hematologic, and serologic findings in dogs with Ehrlichia ewingii infection. Design - Retrospective study. Animals - 15 dogs. Procedure - In all dogs, infection with E ewingii was confirmed with a polymerase chain reaction (PCR) assay. Follow-up information and clarification of information recorded in the medical records was obtained by telephone interviews and facsimile correspondence with referring veterinarians and owners. Results - Fever and lameness were the most common findings with each occurring in 8 dogs. Five dogs had neurologic abnormalities including ataxia, paresis, proprioceptive deficits, anisocoria, intention tremor, and head tilt. Neutrophilic polyarthritis was identified in 4 dogs. No clinical signs were reported in 3 dogs. The predominant hematologic abnormality was thrombocytopenia, which was identified in all 12 dogs for which a platelet count was available. Reactive lymphocytes were seen in 5 of 13 dogs. Concurrent infection with another rickettsial organism was identified in 4 dogs. Of the 13 dogs tested, 7 were seroreactive to E canis antigens. Morulae consistent with E ewingii infection were identified in neutrophiis in 8 dogs. Treatment with doxycycline, with or without prednisone, resulted in a rapid, favorable clinical response in the 9 dogs for which follow-up information was available. Conclusions and Clinical Relevance - Results suggest that PCR testing for E ewingii infection should be considered in dogs with fever, neutrophilic poly-arthritis, unexplained ataxia or paresis, thrombocytopenia, or unexplained reactive lymphocytes, and in dogs with clinical signs suggestive of ehrlichiosis that are seronegative for E canis. Following treatment with doxycycline, the prognosis for recovery is good.