© 2007 American College of Veterinary Ophthalmologists Veterinary Ophthalmology (2007) 10, 3, 137–142 Blackwell Publishing Inc Ocular manifestations of natural canine monocytic ehrlichiosis (Ehrlichia canis): a retrospective study of 90 cases Anastasia A. Komnenou,* Mathios E. Mylonakis,† Vassiliki Kouti,* Lina Tendoma,* Leonidas Leontides,‡ Eugenia Skountzou,§ Angelos Dessiris,* Alex F. Koutinas† and Ron Ofri¶ *Clinic of Surgery and †Clinic of Companion Animal Medicine, School of Veterinary Medicine, Aristotle University of Thessaloniki, GR-54627, Thessaloniki, Greece; ‡The Laboratory of Epidemiology, Biostatistics and Economics of Animal Production, School of Veterinary Medicine, University of Thessaly, GR-43100, Karditsa, Greece; §Private Practitioner; GR-15561, Athens, Greece; ¶Department of Clinical Sciences, Koret School of Veterinary Medicine, Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel Abstract Objective To investigate the spectrum, prevalence and treatment response rate of ocular manifestations associated with natural canine monocytic ehrlichiosis (CME) due to Ehrlichia canis. Methods The medical records of 90 dogs that were admitted for primary ocular problems and reacted positive for E. canis serum antibodies were reviewed. All the dogs were treated with oral doxycycline. In 79 dogs, a combination of systemic corticosteroids and /or topical anti-inflammatory, mydriatics/cycloplegics and antibacterial agents were applied. Results The dogs ranged from 0.5 to 15 years in age; 55 were male and 35 female. A total of 19 breeds were represented. In the majority of dogs, ocular abnormalities were noticed in conjunction with other CME-induced clinical signs. In 30/90 dogs, ophthalmic signs were the sole presenting complaint. Unilateral (22/90, 24.5%) and bilateral (68/90, 75.5%) uveitis was the most common ophthalmic diagnosis and was classified as anterior, posterior or panuveitis in 58 (64.5%), 8 (8.9%) and 24 (26.6%) of the dogs, respectively. Bilateral uveitis was significantly more common than unilateral uveitis (P < 0.0001), and anterior significantly more common than posterior uveitis (P < 0.0001) or panuveitis (P < 0.0001). In addition, corneal ulceration (12/90, 13.3%), necrotic scleritis (10/90, 11.1%), low tear production (8/90, 8.9%) and orbital cellulitis (3/90, 3.3%) were seen. Of the 45 (50%) dogs with a satisfactory follow-up, 25 (55.5%), 11 (24.5%), and 9 (20%) showed complete, partial and poor response to treatment, respectively. The number of dogs exhibiting complete resolution of the ocular manifestations was significantly higher than those with partial (P < 0.0001) or poor (P < 0.0001) response. Conclusions CME should be considered a major differential for a wide range of ocular manifestations exhibited by dogs residing in the endemic areas of the disease. Anterior bilateral uveitis appears to be the most prevalent ocular lesion and a favorable outcome to systemic and topical treatment may be expected in the majority of the affected dogs. Key Words: dog, Ehrlichia canis, monocytic ehrlichiosis, ocular abnormalities, uveitis Address communications to: A. Komnenou Tel.: +30 2310 994443 Fax: +30 2310 994403 e-mail: natakomn@vet.auth.gr INTRODUCTION Canine monocytic ehrlichiosis (CME), caused by the gram- negative bacterium Ehrlichia canis , is considered an important infectious disease of the dog worldwide. 1 The prevalence and severity of its numerous clinical signs depend on the strain, concurrent infections, host immune reaction, clinical phase of the disease, or other as yet undetermined factors. 1 Subclinical or overt ocular lesions are common features in both natural and experimental E. canis infections, with a prevalence ranging from 15 to 100%. 2–10 Previously reported ocular abnormalities associated with CME have included anterior uveitis, panuveitis, secondary glaucoma, retinal vascular engorgement and tortuosity, chorioretinitis, serous or hemorrhagic retinal detachment, retinal atrophy, choroidal, retinal or vitreal hemorrhages, optic neuritis,