Hematologic recovery in Ehrlichia-infected dogs: A meta-analysis of doxycycline’s therapeutic impact

Canine monocytic ehrlichiosis (CME), caused by Ehrlichia canis, is a globally prevalent tick-borne disease with significant hematologic manifestations, including anemia and thrombocytopenia. Doxycycline is the first-line treatment, but its effects on hematologic recovery remain inconsistently reported. This meta-analysis evaluates the impact of doxycycline on hematologic parameters in E. canis-infected dogs. A systematic search was conducted across PubMed, Scopus, Web of Science, and EMBASE. Five studies (one randomized controlled trial, four non-randomized trials) involving 116 dogs were included. Data on erythrocytes, leukocytes (neutrophils, eosinophils, monocytes, and lymphocytes), platelets, hemoglobin, and hematocrit were extracted. Heterogeneity was assessed using I² statistics, and random-effects models were applied where significant heterogeneity existed (I² > 50%). Doxycycline significantly improved hemoglobin levels (MD: -1.98, 95% CI [-3.06, -0.9], P = 0.003), platelet counts (MD: -53.39, 95% CI [-74.94, - 31.85], P < 0.001), and hematocrit (MD: -6.48, 95% CI [-8.88, -4.08], P < 0.001) compared to healthy controls. Infected treated dogs also showed higher platelet counts (MD: 53.1, 95% CI [24.63, 81.56], P < 0.001) and hematocrit (MD: 4.96, 95% CI [1.47, 8.45], P = 0.005) than untreated infected dogs. No significant differences were observed in leukocyte, neutrophil, monocyte, lymphocyte, or eosinophil counts (P > 0.05). Doxycycline effectively restores key hematologic parameters in CME, particularly platelets, hemoglobin, and hematocrit, reinforcing its role as the primary treatment. These findings support doxycycline’s role in improving key hematologic alterations in CME; however, limited and inconsistent effects on leukocyte subsets and residual gaps versus healthy controls indicate the need for larger trials to consolidate the outcomes about hematologic recovery.