Experimental Parelaphostrongylus andersoni infections in white-tailed deer

Gross and microscopic lesions caused by Parelaphostrongylus andersoni were studied in white-tailed deer (Odocoileus virginianus) infected with large (1000 or 5000) and moderate (200-356) numbers of third-stage larvae. In heavy infections, adult worms caused eosinophilic myositis in the loin and thigh. Masses of eosinophils underwent caseous necrosis surrounded by a granulomatous border. Adult worms, eggs, and larvae were in the lesions. Muscle damage caused by moderate doses was slight. One deer given a moderate dose maintained a patent infection for more than 1 year and was reinfected. Gross lung damage caused by eggs and larvae occurred with both degrees of infection and consisted of firm miliary nodules. Microscopically, the main changes were granulomatous encapsulation of eggs and first-stage larvae in alveolar capillaries, accumulations of eosinophils and mononuclear inflammatory cells in the adjacent alveolar septa, congestion, and interstitial pneumonia.