Isolation of the causative organism of canine encephalitozoonosis.

Spontaneous infection with Encephalitozoon cuniculi resulted in a lethal disease in all but one of a litter of puppies in Texas. The disease was characterized by severe nonsuppurative nephritis, encephalitis and segmental vasculitis. Many protozoa were in renal tubule cells, endothelial cells and brain. The number of organisms decreased and the granulomatous character of the lesions became more prominent as the disease progressed. Sera from affected puppies and their parents reacted in an indirect immunofluorescence test with canine E. cuniculi propagated in vitro. The sera of owners of affected pups were negative.