Apolipoprotein A-1 does not appear to be a suitable acute-phase reaction marker in canine babesiosis and hemoplasmosis

Acute Babesia canis infections in dogs most often cause a marked acute-phase response (APR) influencing lipoprotein metabolism. However, the significance of apolipoprotein A-1 (ApoA-1), a major protein and key determinant of high-density lipoprotein (HDL) formation, as a negative acute-phase protein is unclear. To investigate this topic, 84 dogs were classified in four study groups (SGs): (i) 23 dogs with acute B. canis infection tested PCR-positive; (ii) 26 dogs with high antibody levels against Babesia spp.; (iii) 17 dogs with acute hemotrophic Mycoplasma infections; and (iv) 18 clinically healthy dogs. Complete blood count, total protein, albumin, globulins, triglycerides, cholesterol, and C-reactive protein (CRP) were compared between the SGs and correlation analysis was performed. Results showed that ApoA-1 concentrations did not differ significantly between SGs but were decreased in SG I compared to SG II-IV. Significantly different concentrations of CRP and triglycerides indicated APR in dogs with acute B. canis infection. ApoA-1 concentrations showed a moderate negative correlation with cholesterol and a moderate positive correlation with eosinophils. No statistical significance was found when comparing dogs tested serologically positive for Babesia spp., dogs with hemotrophic Mycoplasma infections, and clinically healthy dogs. Overall, APR was observed in dogs with acute B. canis infections with significantly elevated triglycerides and CRP, but the value of ApoA-1 as a negative acute-phase protein is questionable. No evidence for APR was observed in Babesia spp.-seropositive dogs and those with hemotrophic Mycoplasma infection.