Serum Amyloid A levels and α2- and Gamma globulins on Serum Protein Electrophoresis in cats exposed to and infected with Leishmania infantum

Background: Although dogs are the main reservoir host of Leishmania infantum, recent investigations indicate a role for cats in its epidemiology. Feline leishmaniosis (FeL) remains poorly characterised, partly due to the lack of diagnostic tools. This study aimed to compare Serum Amyloid A (SAA) levels and serum protein electrophoresis (SPE) profiles (specifically, α2- and gamma globulins) in cats naturally exposed to or infected by L. infantum from southern Italy with those of healthy controls and of cats with neoplastic or inflammatory conditions from non-endemic areas.Methods: Serum or plasma samples from four cohorts of cats were analysed for SAA and by SPE, i.e G1: healthy controls from Leishmania-non-endemic regions of Switzerland, G2: cats pre-diagnosed with neoplastic or inflammatory conditions from the University of Cambridge’s sample archive, G3: L. infantum seropositive, qPCR-negative cats from southern Italy, G4: L. infantum seropositive and qPCR-positive cats from southern Italy. SAA data was assessed for normality using the Kolmogorov-Smirnoff and Shapiro-Wilk normality tests, then compared using a homogeneity of variance test for non-parametric data; the Kruskall-Wallis test, followed by Dunn’s multiple comparison test were used to compare SAA serum levels between groups. The Fisher’s Exact test was used to assess statistically significant differences in the numbers of animals displaying elevated gamma globulins and increased α2-globulins between groups.Results: Overall, 68 samples were analysed (G1 n=16, G2 n=20, G3 n=20, G4 n=12). Cats previously exposed to and/or infected with L. infantum, as well as cats suffering from neoplastic and inflammatory conditions showed significantly higher SAA levels (median values G1=0.00 (0.00-0.00) mg/L, G2=0.85 (0.00-49.55) mg/L, G3=0.00 (0.00-4.53) mg/L, G4= 0.00 (0.00-7.5) mg/L), and higher percentages of cats with increased α2-globulins (G1=20.0% ±10.3, G2=80.0% ±8.9, G3=70.0% ±10.2, G4=75.0% ±12.5) and gamma globulins (G1=0.0% ±0, G2=65.0% ±10.7, G3=50.0% ±11.2, G4=58.3% ±14.2) than healthy control cats. For all three markers, there was no significant difference between G2, G3 and G4.Conclusions: This study indicates that, whilst levels of gamma and α2-globulins and SAA are significantly elevated in cats infected by L. infantum, they cannot be used to differentiate between L. infantum infection or exposure and neoplastic or inflammatory conditions. Nevertheless, these indicators might assist monitoring of ongoing FeL if further studies indicate reduction during or following successful treatment.