Brain and spinal cord lesions in encephalitozoonosis in blue foxes. Transmission and scanning electron microscopic studies.

The brains and spinal cords from 3 young blue foxes suffering from acute to subacute encephalitozoonosis, were examined by transmission and scanning electron microscopy. Parasitophorous vacuoles (PV) were demonstrated more frequently in vascular smooth muscular cells than in endothelial cells. The present study also indicated that the parasite has great affinity for neurons, including their processes. In addition, PV occurred in macrophages and probably also in intravascular monocytes. PV were readily differentiated from phagosomes by the bleb formations of the limiting membrane. An accumulation of host cell mitochondria near the PV in areas where developmental stages were attached, was a most striking feature. The inflammatory lesions, mainly of the granulomatous type, were almost constantly associated with the presence of released parasites, both in vascular walls and the nervous tissue. Phagocytosed parasites were probably killed by the lysosomal enzymes, although the spores were only slowly degraded.