The development of Pneumostrongylus tenuis in the central nervous system of white-tailed deer

The central nervous systems of five fawns (Odocoileus virginianus borealis), infected experimentally with Pneumostrongylus tenuis, were studied histologically 10, 20, 25, 30, and 40 days after infection. In the 10–30 day fawns young developing worms were found in dorsal horns of the grey matter of all regions of the spinal cord. A few worms were found in white matter and in the medulla oblongata. In the fawn autopsied 40 days after infection all but one of about 25 worms found were in the subdural space.

Worms in the grey matter usually lay in cell-free tunnels surrounded by compressed neural tissue. There was little reaction of, or cellular infiltration in, surrounding tissue. Malacia was absent in all parts of grey matter. The central canal was normal and the brain, other than the medulla oblongata, was not involved. In the white matter, scattered single myelin sheath degeneration as well as degeneration and disappearance of axis cylinders were common. Occasionally there were tiny malacic areas in white matter, especially near worms. Infiltrations of eosinophils, lymphocytes, and plasma cells were commonly observed in and on the dura mater, the epineurium, ganglion capsules, and other tissues of the epidural space.

The relative dearth of histopathologic findings helps to explain the rarity and slightness of neurologic signs in infected fawns and is indicative perhaps of a long and well established host-parasite relationship. This is in contrast to the situation in moose (Alces a. americana) where severe traumatic damage to the spinal cord by P. tenuis is associated with ataxia and paralysis.

An examination of wild moose exhibiting neurologic signs, in Ontario

The central nervous systems of three wild moose (Alces a. americana) exhibiting neurologic signs, in the Kenora district of Ontario, Canada, were studied histologically. A diagnosis of cerebrospinal nematodiasis (Pneumostrongylus tenuis) was made in all three animals.

Electricity in Volcanic Clouds

In November of 1963 an oceanic volcano produced an island, Surtsey, just off the southern coast of Iceland. The volcanic crater was often flooded with sea water. Vigorous eruptions of steam and tephra were accompanied by an enhancement of the normal fine-weather potential gradient, and lightning was often observed. Measurements of atmospheric electricity and visual and photographic observations lead us to believe that the electrical activity is caused by the ejection from the volcano into the atmosphere of material carrying a large positive charge. The concentration of charge in the eruption plume as it issued from the orifice of the volcano is estimated to be of the order of 10(5) or 10(6) elementary charges per cubic centimeter.