Annual prevalence of Parelaphostrongylus tenuis for white-tailed deer in Maine varied from 63 to 80 percent during 1968-70. Prevalence was significantly lower (P<.01) in fawns than older deer. Adult females had a significantly higher (P<.01) prevalence of P. tenuis than adult males. Females also had a slightly greater average number of P. tenuis per infected animal. An area of relatively low deer density had the highest overall prevalence (81.2 percent), while a region of relatively high deer density had the lowest (59.1 percent).

P. tenuis was most frequently found in the tentorium cerebelli, the falx cerebri and the dura mater. No significant differences in distribution were noted in deer of various sexes and ages. However, 2 percent of the P. tenuis found in does apparently had penetrated the neural parenchyma of the brain.