Understanding Ehrlichia canis Infections in Dogs of Costa Rica: Hematological Findings and Indicative Clinical Signs

Background: A cross-sectional study combining different serological and molecular techniques for the detection of Ehrlichia canis in dogs was carried out to determine hemopathological findings and suggestive clinical signs associated with acute, subclinical and chronic infections in the dog population of Costa Rica. Objectives: The present study describes and analyzes, in a more representative sampling frame, the clinical and hematological presentation of E. canis infection in dogs of Costa Rica in all its clinical stages. Methods: A descriptive analysis of the clinical signs was performed from a 441-dog sample. Serological and molecular techniques for the detection of Ehrlichia canis in dogs were applied. One and two-way ANOVA were carried out to determine the effect of the infection status on the hematological parameters. Results: A total of 0.7% (3/407) dogs were found with acute (seronegative but PCR positive), 29.7% (121/407) with subclinical (seropositive and PCR negative), and 2.5% (10/407) with chronic (seropositive and PCR positive) E. canis infections. Significant hemopathological findings were determined in dogs with acute (thrombocytosis), subclinical and chronic (anemia, thrombocytopenia, leukopenia) E. canis infections. Conclusions: Future studies must determine if dogs with subclinical E. canis infections eliminated the agent without any medication, or if they continue to be persistently infected, and will develop the chronic disease at some point in their lives.