The aims of this study were: the identification of proteins differentially represented in the serum proteome of dogs with leishmaniosis after treatment and the verification of one selected protein as a possible biomarker for treatment monitoring. Serum samples from five dogs with leishmaniosis, before and after treatment were pooled into two groups and analysed using 2-dimensional electrophoresis followed by mass spectrometry analysis (MS). The MS analysis allowed the identification of 8 proteins differently expressed. APO-A1 was selected and an immunoturbidimetric assay was validated for its measurement in dogs. Significantly decreased concentrations of APO-A1 in dogs with leishmaniosis and a significant increase after a good response to the treatment were observed, suggesting that APO-A1 could be a potential biomarker of treatment monitoring with the advantages of an automated measurement. (C) 2016 Elsevier Ltd. All rights reserved.