Background: Leptospirosis is a neglected but widespread zoonotic disease throughout the world. The vast majority of mammals are hosts of Leptospira spp., including domestic cats. Though clinical signs of active leptospirosis are generally mild in cats, chronic infections might result in renal injury. However, there is no consensus either on the clinical presentation nor on the disease diagnosis in cats. The study of acute-phase proteins (APPs) and biomarkers of oxidative status would contribute to knowledge about the development ofthe disease in cats. In this report, we evaluated four APPs: Serum amyloid A-SAA, Haptoglobin–Hp, albumin and Paraoxonase 1-PON1 and the antioxidant response through Total Antioxidant Capacity-TAC, in 13 free-roaming cats naturally infected by pathogenic leptospires and 19 leptospires-free cats, through a Principal Component Analysis (PCA). Results: DNA positive cats showed higher serum SAA and Hp concentrations than seropositive cats and their leptospires-free counterparts. DNA positive individuals, however, had lower serum PON1 activity and albumin concentrations than seropositive and leptospires-free cats. On the other hand, the increase in TAC serum concentrations was positively associated with anti-leptospiral antibodies titre. The PCA retained two principal components (PC1 and PC2), explaining 60.1% of the observed variability of the inflammatory proteins and the antioxidant TAC. PC1 was mainly associated with an inflammatory process, whereas PC2 correlated with the antioxidant status. The most contributing variables in PC1 where albumin (27.46%), SAA (24.71%), Hp (21.56%) and PON1 (20.69%). Variables with significant contribution to the PC2 were the antibody titre against Leptospira spp. (48.41%) and TAC (35.04%). Overall the PCA revealed differences in inflammatory and antioxidant biomarkers in cats naturally infected with leptospires compared to leptospires-free cats.Conclusions: Increases in Serum SAA, Hp, and decreases in serum albumin concentrations and PON1 activity indicate an acute phase response in infected, DNA positive cats. Moreover, we found an increase in TAC serum concentrations indicating an antioxidant response in this infection, which is proportional to the antibody titre and not to the presence of bacterial DNA.

Background: Leptospirosis is a neglected but widespread zoonotic disease throughout the world. The vast majority of mammals are hosts of Leptospira spp., including domestic cats, species in which no consensus has been reached on the clinical presentation or diagnosis of the disease. The study of acute-phase proteins (APPs) and biomarkers of oxidative status would contribute to knowledge about the course of the disease in cats. In this report, we evaluated four APPs: Serum amyloid A-SAA, Haptoglobin–Hp, albumin and Paraoxonase 1-PON1 and the antioxidant response through Total Antioxidant Capacity-TAC, in 13 free-roaming cats naturally infected by pathogenic leptospires and 19 leptospires-free cats, through a Principal Component Analysis (PCA). Results: The PCA retained two principal components (PC1 and PC2), explaining 60.1% of the observed variability of the inflammatory proteins and the antioxidant TAC. PC1 was mainly associated with an inflammatory process, whereas PC2 correlated with the antioxidant status. The most contributing variables in PC1 where albumin (27.46%), SAA (24.71%), Hp (21.56%) and PON1 (20.69%). Variables with significant contribution to the PC2 were the antibody titre against Leptospira spp. (48.41%) and TAC (35.04%). Overall, the PCA revealed differences in inflammatory and antioxidant biomarkers in cats naturally infected with leptospires compared to leptospires-free cats.Conclusions: Increases in Serum SAA, Hp, and decreases in serum albumin concentrations and PON1 activity indicate an acute phase response in infected, DNA positive cats. Moreover, we found an increase in TAC serum concentrations indicating an antioxidant response in this infection, which was proportional to the antibody titre and not to the presence of bacterial DNA.