Atypical findings in 16 cases of canine ehrlichiosis.

Sixteen cases of clinically and serologically diagnosed canine ehrlichiosis were studied retrospectively. Findings not previously reported included diffuse, pulmonary interstitial radiopacities; weak-positive results for blastomycosis, using agar gel immunodiffusion; normal platelet counts; hemorrhage despite platelet counts greater than 100,000/mm3, and positive results for platelet factor 3 and antinuclear antibody assays. These atypical findings showed that the differential diagnosis of canine ehrlichiosis, blastomycosis, immune-mediated thrombocytopenia, and primary nasal lesions may be confusing, warranting careful assessment. The increased release of platelet factor 3 and the finding of antinuclear antibodies supported an immune mechanism in the pathogenesis of canine ehrlichiosis, as suggested by previous experimental studies.