Chronic steroid administration does not suppress Plasmodium development and maturation

The objective of this study was to investigate the influence of constant steroid uptake on the Plasmodium yoelii infection rate and parasite maturation. On the animal model, we examined the effect(s) of dexamethasone (Dx), the general drug used for self-treatment by Thai villagers. Ten female ICR mice were subjected to oral administration of 0.5 mg/kg Dx for 40 days, whereas other ten were given drinking water only before P. yoelii 17X (lethal) strain inoculation. Parasite-infected erythrocytes were verified by Giemsa staining under light microscope. The differences of infectivity and maturation were evaluated by Student's t test. Parasitemia was detected in both groups on day 1 and increased until day 6 with similar infection rates. Significant lower numbers of ring, trophozoite, and schizont stages in the control group at the same time compared to Dx-treated mice were noted. The parasite maturation in infected Dx-treated mice appeared faster in comparison to the control. We conclude that the chronic taking of Dx suppresses the host immunity, without any suppressive effects on the parasite development and maturation, and, on the contrary, increases the development and maturation of P. yoelii.