Evaluation of serum levels of CRP and TNF-α in dogs infected with Ehrlichia canis and Anaplasma phagocytophilum

Abstract

Background: Canine monocytic ehrlichiosis (CME) and canine granulocytic anaplasmosis (CGA), caused by Ehrlichia canis and Anaplasma phagocytophilum, are tick-borne diseases prevalent in dogs. Both trigger systemic inflammation, with C-reactive protein (CRP) and tumor necrosis factor-alpha (TNF-α) as potential severity biomarkers. Aim: This study aimed to compare serum CRP and TNF-α in CME, CGA, and co-infected dogs and assess their relationships with hematological, biochemical, and liver enzyme changes. Methods: In 134 dogs showing clinical signs of CME/CGA, infections were confirmed using SNAP® 4Dx® Plus, indirect immunofluorescence assay, and polymerase chain reaction (PCR). CRP and TNF-α were quantified using canine-specific enzyme-linked immunosorbent assay kits. Results: Of the dogs tested, 112 (83.6%) were seropositive and 77 (68.8%) were PCR-positive (E. canis: 27; A. phagocytophilum: 29; co-infection: 21). The co-infected group had the highest levels of CRP (135.2–154.8 mg/l) and TNF-α (161.5–174.0 pg/ml), significantly exceeding those of CME (104.6–120.9; 148.7–162.2 pg/ml), CGA (88.5–104.4; 140.1–156.5 pg/ml), PCR-negative (33.1–45.8; 12.3–18.9 pg/ml), and control groups (0.9–4.0; 0.2–2.3 pg/ml) with p < 0.001. Thrombocytopenia was common in all infected groups, with the lowest platelet counts in co-infected dogs (median 106.0 × 109/L, p < 0.001). Aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly elevated only in co-infected dogs (ALT: 89.25 U/l; AST: 69.38 U/l; p < 0.001). CRP correlated moderately with ALT/AST; TNF-α showed weaker positive associations. Conclusion: CRP and TNF-α are valuable indicators of systemic inflammation in CME and CGA, with maximal increases and stronger links to liver injury in co-infections, supporting their use in diagnosis and prognosis.