THE INCIDENCE, DEVELOPMENT, AND EXPERIMENTAL TRANSMISSION OF PNEUMOSTRONGYLUS TENUIS DOUGHERTY (METASTRONGYLOIDEA: PROTOSTRONGYLIDAE) OF THE MENINGES OF THE WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS BOREALIS) IN ONTARIO

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Abstract
Pneumostrongylus tenuis was found throughout the year in the cranium of 41% of 172 adult deer examined in Algonquin Park. Incidence was higher in summer (46%) than winter (24%). Two fawns were infected (October and March). Worms also occurred on the spinal dura mater and in veins of the dura. Thus, incidence of infection was higher than indicated by examinations of craniums. Larvae developed in species of Discus, Zonitoides, Deroceras, Triodopsis, Stenotrema, and Lymnea sp. Four fawns were infected experimentally. Fourth- and fifth-stage larvae were found in the brain and spinal cord of one fawn examined at 25 days. Fifth stages were found in the tissue and between the meninges of the spinal cord of a fawn examined at 40 days. Subadults were found on the spinal and cerebral dura mater of a fawn autopsied at 50 days. The final fawn passed larvae 91 days after exposure. At 115 days after exposure, mature worms were found on or in the cerebral dura; two were found in the intercavernous sinus. The inflamed dura was covered by haemorrhagic, fibrous exudate containing larvae and developing eggs. Eggs and larvae were found in vessels in the pia-arachnoid and near veins in the dura. Lungs contained minute nodules with one to three eggs. Undeveloped eggs, reaching the lungs via the blood, formed embolisms that fibrosed. In regions of the lungs with numerous developing eggs and larvae there was congestion, inflammation, haemorrhage, and fibrosis of interstitial tissue.