Misdiagnosis of canine monocytic ehrlichiosis: why do we still risk animal lives?

Canine Monocytic Ehrlichiosis (CME) is a tick-borne disease caused by Ehrlichia canis that manifests as acute, chronic, or subclinical forms without specific clinical symptoms. This disease is diagnosed using clinical and laboratory findings (blood smears, molecular techniques, and serology). This study aimed to demonstrate the occurrence of false-positive results for Ehrlichia spp. in veterinary clinical practice. Seventy dogs with positive blood smears before treatment for Ehrlichia spp. subjected to doxycycline and imidazole treatment were analyzed using hematological examination, polymerase chain reaction (PCR), and indirect immunofluorescence assay. PCR analysis identified no samples positive for E. canis according to PCR analysis, while serological techniques showed a frequency of 51.4% in dogs with antibodies (IgG) against Ehrlichia spp. There was a correlation between hyperproteinemia and titers > 10,240. Nonspecific changes occurred in 24.3% (17/70) of the patients with CME, such as anemia, leukopenia, and thrombocytopenia. The results indicated that the blood count and blood smear analysis were insufficient for diagnosis and that positive serological results associated with hematological changes suggestive of ehrlichiosis in dogs can be incorrectly assigned by a veterinarian, putting animals at risk.