The incidence and degree of infection by P. tenuis was studied in western Virginia deer herds (Odocoileus virginianus). The objectives of the research were (1) to determine the distribution of pneumostrongylids in the white-tailed deer in seven western Virginia counties and (2) to correlate incidence and degree of infection by pneumostrongylids with deer age, sex, geographic location, and physical condition. Specimens were collected from Shenandoah, Augusta, Bath, Rockbridge, Botetourt, Giles, and Craig counties. Deer heads were obtained from hunters at check stations. Three-hundred and nine deer heads, 230 does and 79 bucks, were examined for P. tenuis and 73% were infected. The majority of the worms (68%) were found on the dorsal surface of the brain. The range of infection was 1-13 worms. In addition, lung and fecal specimens were collected. Fifty per cent of the lung specimens were infected, but no larvae were round in the fecal material. There appeared to be an equal likelihood of infection by P. tenuis in deer of either sex less than 1 1/2 years of age. There was no difference between sexes in the severity of infections in deer less than 1 1/2 years old. Deer of either sex older than 3 1/2 years also had an equal likelihood of infection by P. tcnuis, but females between 1 1/2 and 3 1/2 years were more likely to be infected than males. Females older than 1 1/2 years of age had significantly more worms per infection than males of the same age. There was no relationship be,tween weight and incidence of infection in deer less than 1 1/2 years or older than 3 1/2 years. However, a relationship did exist between the weight of the 1 1/2 to 3 1/2 years age group and the incidence of infection, in that the heavier deer were more likely to be infected. Deer less than 1 1/2 years of age had a lower incidence of infection than older deer and fewer worms per infection than older deer. There was a significant difference in the incidence of infection between surveyed counties; however, there was no statistically significant difference between counties in the severity of infections. Further research concerning pathogenic effects of P. tenuis on the white-tailed deer is imperative prior to employment of any control methods. P. tenuis may be a serious pathogen, but this research indicates that the deer-Po tenuis relationship is a relatively stable and common association, with host populations seldom adversely affected by the parasites.
