Glomerulotubular pathology in dogs with subclinical ehrlichiosis

Abstract

Subclinical stage of ehrlichiosis is characterized by absence of clinical or laboratory alterations; however, it could lead to silent glomerular/tubular changes and contribute significantly to renal failure in humans and animals. The aim of this study was to evaluate glomerular and tubular alterations in dogs with subclinical ehrlichiosis. We evaluated renal biopsies of 14 bitches with subclinical ehrlichiosis and 11 control dogs. Samples were obtained from the left kidney, and the tissue obtained was divided for light microscopy, immunofluorescence, and transmission electron microscopy. Abnormalities were identified by light microscopy in 92.9% of dogs with ehrlichiosis, but not in any of the dogs of the control group. Mesangial cell proliferation and synechiae (46.1%) were the most common findings, but focal segmental glomerulosclerosis and ischemic glomeruli (38.4%), focal glomerular mesangial matrix expansion (30.7%), mild to moderate interstitial fibrosis and tubular atrophy (23%), and glomerular basement membrane spikes (23%) were also frequent in dogs with ehrlichiosis. All animals with ehrlichiosis exhibited positive immunofluorescence staining for immunoglobulins. Transmission electron microscopy from dogs with ehrlichiosis revealed slight changes such as sparse surface projections and basement membrane double contour. The subclinical phase of ehrlichiosis poses a higher risk of development of kidney damage due to the deposition of immune complexes.

Fig 1. Light microscopy findings.

Control group: (A) Glomerular structure preserved, with no evidence of alterations. Masson’s Trichrome (x400). (B) Preserved glomerular structure, without evidence of alterations. Jones methenamine silver (JMS) (x630). Ehrlichiosis group: (C) Membranous-like glomerulopathy with diffuse and regular thickening of the glomerular capillary walls, frequently with mild and segmental mesangial proliferation. Masson’s trichrome (x400). (D) Synechia with evident segmental glomerulosclerosis (arrow). Masson’s Trichrome (x400). (E) Membranous-like glomerulopathy with sparse surface projections (spikes) along sub-epithelial surface of the glomerular basement membrane (arrow) (JMS) (x630).

Fig 2. Immunofluorescence and transmission electron microscopy findings.

Control group: (A) Negative immunofluorescence. (x400). Ehrlichiosis Group: (B) Strong diffuse granular positivity for IgM in mesangium. (x400). (C) Electron microscopy evidencing sub-epithelial (arrow) and (D) sub-endothelial deposits (arrow) and capillary duplication of glomerular basement membrane (arrowhead) and effacement of the podocyte foot processes (dashed circle).