Erythrocyte surface sialic acid depletion as predisposing factor to erythrocyte destruction in sheep experimental model of African Trypanosomosis: A preliminary report

Changes in erythrocyte surface (ESSA) and free serum sialic (FSSA) profiles that could occur sequel to trypanosome infection with consequent destruction of red blood cells by mononuclear phagocytic system were investigated in an experiment in which 8 sheep were infected with Trypanosoma congolense (T. congolense), while six other sheep served as uninfected controls. The infection with T. congolense caused rapid decline in ESSA concentration and packed cell volume (PCV) in sheep. Concomitantly, rise in mean FSSA concentration was observed in the T. congolense infected sheep. Major periods of decline in ESSA concentration and greatest increase in FSSA concentration coincided with period of highest parasitaemia levels. The ESSA concentration in the infected sheep stabilized as the infection aged but the concentration of this parameter remained at comparatively lower levels than that in the control sheep and relative to the pre-infection value on day 0 of infection. This ESSA level in T. congolense-infected sheep was maintained with only minor fluctuations up to the termination of the experiment. PCV, ESSA and FSSA concentrations remained relatively unchanged in the control group throughout the course of the experiment that lasted for 53 days. The post-infection mean values of FSSA and ESSA in the T. congolense-infected and control sheep were 2.3 +/- 0.5mg/ml and1.7 +/- 0.9mg/ml, and 1.9 +/- 0.2mg/ml and 2.1 +/- 1.2mg/ ml, respectively. The respective values of PCV, ESSA and FSSA concentrations in the infected sheep differed significantly (P0.05) from those in the control sheep. Further investigations to elucidate the possible roles of sialyltransferase in the recovery of ESSA and, consequently, erythrocyte mass in trypanosome-infected animals are undoubtedly needed.