Ecology of porcupines (Erethizon dorsatum) and Colorado tick fever virus in Rocky Mountain National Park, 1975-1977.

The involvement of porcupines, Erethizon dorsatum (L.), in the ecology of Colorado tick fever (CTF) virus in Rocky Mountain National Park was investigated from 1975 to 1977. Porcupine dens and feeding activity were found mostly on rocky knolls or on south-facing slopes within open stands of the montane coniferous forest, and 20 adult porcupines were trapped or captured by hand at those locations. An average of 24.6 +/- 5.4 adult Dermacentor andersoni Stiles ticks were found per animal (annual range, 17.5-31.4 ticks). The minimum CTF virus infection rate of the ticks removed from porcupines varied from 129 to 257, whereas for questing adult D. andersoni ticks from the same geographic area was 205 in 1976. No virus was isolated from the 20 animals, but 85% had neutralizing antibody against CTF virus. Porcupines utilize the same habitats described for the CTF ecosystem in Rocky Mountain National Park and appear to be an important host for adult D. andersoni.