Pathogenesis and red blood cell destruction in haemoglobinaemic leptospirosis

Sequential morphological changes were seen in RBCs, spleen and liver from hamsters during the development of haemoglobinaemia following infection with Leptospira interrogans serovar ballum. Spleens from pre-haemoglobinaemic hamsters showed sequestration of RBCs and erythrophagocytosis but to a lesser degree than was seen in the haemoglobinaemic hamsters. Erythrophagocytosis and RBC sequestration were also seen in the liver, particularly in the haemoglobinaemic animals. None of these changes was seen in the RBCs, spleens and livers from moribund and dead hamsters suffering from non-haemoglobinaemic disease resulting from infection with Leptospira interrogans serovar pomona. Intracellular leptospires were readily identifiable within the spleens and livers of hamster infected with both ballum and pomona. It is suggested that leptospiral toxins affect RBC metabolism and eventually RBC morphology. The affected cells are detected and removed by the reticulo-macrophage system, usually before intravascular haemolysis can take place. If the toxins affect a certain enzyme or biochemical pathway, there are sufficient normal metabolic differences in RBCs between animals of different species and, in the same species of animal, between the same and different aged animals, to explain the differing susceptibilities of the RBCs to leptospiral toxins.