Effect of splenectomy on Trypanosoma lewisi infection in young rats.

The effect of splenectomy on animals infected with Trypanosoma lewisi is unclear, and previous reports are inconclusive or conflictive. We splenectomized rats of different ages after they had been infected with T. lewisi. Female Sprague-Dawley rats, Hemobartonella-free, were assigned to four groups according to weight: 80, 108, 140, and 170 g. Each group had splenectomized, sham-operated, and nonoperated control subgroups, all infected with T. lewisi (0.5 ml of 10(6) parasites per ml) 90 h before surgery. Before surgery, parasite levels in host blood were similar. At 24 h after splenectomy in all groups, regardless of weight, blood parasite levels were much higher than they were in sham-operated or control animals (P less than 0.001 to P less than 0.0001; analysis of variance). Younger rats (80 and 108 g) had a higher mortality rate after splenectomy than sham-operated and control animals. Older rats (150 and 170 g) had no mortality. These results show the impact of age and the importance of the spleen on parasite-host interactions in rats infected with T. lewisi.