Abstract
The kidneys of seven dogs with natural infections of heartworm disease, four dogs with experimental infections, and six control (uninfected) dogs raised in isolation were examined by light, fluorescent, and electron microscopy. Swelling and fragmentation of the basement membranes accompanied by denudations of endothelial cells and fusion and atrophy of foot processes occurred in the glomeruli of dogs with heartworm disease, but not in control dogs. The severity of tissue damage correlated with the degree of microfilaremia. There was no evidence that the glomerular lesions were caused by immune complexes deposited in the basement membranes; and the alterations of glomerular capillaries were probably caused by motile microfilariae in the capillaries.