Neurologie Disease in Moose Infected Experimentally with Pneumostrongylus tenuis from White-Tailed Deer

Abstract

An experiment was undertaken to test the hypothesis that moose neurologic disease is cerebrospinal nematodiasis. Two moose calves ( Alces a. americana) were infected with Pneumostrongylus tenuis derived from white-tailed deer ( Odocoileus virginianus borealis). Two to three weeks later both calves became lethargic and seemed unwilling to rise. This weakness and ataxia became progressively more pronounced and terminated in paraplegia. One calf was autopsied on the 40th day, the other on the 60th day. Fifth-stage P. tenuis were found in saline in which the central nervous system of the first calf had been placed. Numerous subadult worms were found in subdural spaces of the cranium and vertebral column of the second moose.Histological study revealed additional worms and traumatic damage in the central canal and dorsal horns of the cord of both calves. Focal malacia with micro-cavitation was found in all regions of the cord. Infiltrations of round cells and eosinophils in the leptomeninges, the ventral fissure and the dorsal sulcus, perivascular cuffing with round cells, petechial haemorrhages, neuron degeneration and loss, as well as swelling and disappearance of axis cylinders and myelin sheaths were observed.The known distribution and characteristics of neurologic disease in wild moose supports the hypothesis that P. tenuis is the ætiological agent.