Spontaneous mesangiocapillary glomerulonephritis in Finn cross lambs from Alberta.

A spontaneous mesangiocapillary glomerulonephritis occurred in three, one to three month old Finnish Landrace cross lambs from a flock in northern Alberta. The ram was a purebred Finn sheep, and the ewes were Finn-Rambouillet and Finn-Suffolk-Rambouillet crosses. The lambs were found dead without previous clinical signs. Histologically there was marked thickening of glomerular capillary basement membranes, proliferation of mesangial cells, and peri-glomerular fibrosis. An interstitial infiltration of plasma cells and lymphocytes was present with occasional tubular degeneration and proteinaceous cast formation. Focal leukoencephalomalacia was present in one lamb. Electron microscopy demonstrated deposition of electron-dense deposits in a subendothelial location with occasional fusion of overlying foot processes in glomerular capillaries. Indirect immunofluorescence studies demonstrated positive staining material in glomerular capillary walls. These findings in Finnish Landrace cross lambs are characteristic of mesangiocapillary glomerulonephritis, a condition heretofore not reported in North America.