Time factor and eosinophil count in relation to experimental Schistosoma mansoni infection.

The effects of diurnal variations of eosinophils on hostparasite relationship was studied in mice primarily exposed to S. mansoni infection. The eosinophil counts of 20 control normal mice showed different variations at different hours of the day with maximum level at midday and the minimum level at midnight. At these times, 2 groups of mice, each consists of 30 mice, were infected by about 100 S. mansoni cercariae. The infected mice in both groups showed more or less the same results as regards the worm burden, egg counts in tissues and histopathological changes in livers. Both infected groups showed marked eosinophil elevation versus normal control group yet the difference in-between them was insignificant. This means that the normal physiological variation in eosinophils in normal mice is useless in protection against infection. Complete ablation of eosinophils from animal using antieosinophilic sera, is essential for any study on eosinophils in relation to infection.