Evaluation of serum sialic acid level in buffaloes naturally infected with Theileria annulata.

Tropical theileriosis, caused by Theileria annulata, is the most economically important disease of domestic buffaloes and causing major losses in livestock production in Iran. Sialic acids are often involved in interaction between the cells and the infectious agents by regulating the molecular relations as well as mediating a variety of cell-cell adhesion processes in the immune response. This study was conducted to assess the effect of T. annulata infection on sialic acid concentration in blood sera in naturally infected buffaloes. T. annulata-infected (n = 22) and uninfected control (n = 20) adult buffaloes were selected. Theileria infection was revealed by Giemsa-stained peripheral blood and was confirmed by nested-PCR using T. annulata-specific primers. Based on the detected parasitemia, the infected animals were subgrouped into low <1 %, moderate 1-3 %, high 3-5 %, and very high >5 %. Hematological parameters and the concentrations of total sialic acid (TSA), lipid-bound sialic acid (LBSA), and protein-bound sialic acid (PBSA) were measured and correlated to parasitemia. The results showed significant differences (P < 0.05) in red blood cells (RBCs), packed cell volume (PCV), hemoglobin (Hb), and sialic acid concentrations between infected and control groups. As the parasitemia increased accordingly, a significant decrease in RBCs, PCV, Hb and increase in the mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), and serum sialic acids was observed. We concluded that T. annulata infection could elevate the serum sialic acid concentrations. The increased levels of serum sialic acid concentrations during parasitemia presumably stimulate the host immune response and influence the parasite-host cell adhesion.