Pathogenesis of renal lesions in haemoglobinaemic and non-haemoglobinaemic leptospirosis.

Hamsters were infected with Leptospira interrogans serovar ballum or Leptospira interrogans serovar pomona and the kidney lesions were compared by light and electron microscopy. Ballum and pomona both caused severe clinical signs and death within 6 days in some animals, although only ballum was associated with red blood cell destruction and haemoglobinaemic nephrosis. With ballum infections it is difficult to distinguish degenerate changes resulting from leptospiral "toxins" from those resulting from hypoxia and haemoglobinaemic nephrosis because large numbers of organisms and haemoglobinaemia coincide shortly before death. Although large numbers of leptospires were seen within the renal interstitium and blood vessels in animals dying shortly after infection, organisms were seen only in the proximal convoluted tubules of those surviving until 14 days. It is thought that leptospires are carried by the bloodstream and migrate at random throughout all body tissues. When antibody develops, only those in the renal tubules remain. The random migration results in some leptospires entering tubules at all levels of the nephron but there are good grounds for believing that the normal changes in composition of the glomerular filtrate as it passes through the nephron are increasingly deleterious to leptospiral survival. This probably explains why leptospires are found predominantly in the proximal convoluted tubules of animals after the development of specific immunity.