Thrombocytopenia and anemia related to retinal detachment in dogs infected with Ehrlichia canis and Anaplasma platys

In Thailand, five species of Ehrlichia (E. canis, E. chaffeensis, E. equi, E. risticii and Anaplasma platys) have been reported to infect dogs. Although ehrlichial infections can cause ocular disorders, the severity and type of ocular disorder varies between individual infected dogs. The aims of this study were to determine the factors associated with retinal detachment and to investigate the species of Ehrlichia that cause ocular disorders in natural infected dogs. In the present study, ocular examination, complete blood count and total protein measurement were performed in 134 dogs brought into an ophthalmology clinic. A 310 bp fragment of the Ehrlichia 16s rRNA gene was amplified by nested-PCR and direct DNA sequenced. Thirty-eight of these dogs were found to be positive for Ehrlichia 16s rRNA, of which the sequence analysis suggested 34 and 4 dogs were infected with E. canis and A. platys, respectively, with no multiple infections or other Ehrlichia species detected. The most common ocular disorders in dogs infected with E. canis were blindness, keratoconjunctivitis sicca and retinal detachment, while blindness and retinal detachment were found in A. platys-infected dogs. Hematological disorders were found anemia, thrombocytopenia and hyperproteinemia. Odd ratio analysis showed that thrombocytopenia and anemia were likely important factors for increasing retinal detachment risk. In this study, only E. canis and A. platys closely relate to be causative agents of ocular disorders in infected dogs. To the best of our knowledge, this is the first report of A. platys as a causative pathogen of both anterior and posterior uveitis in clinical situations.