Disease Ecology of a Low-Virulence Strain in a Free-Ranging Desert Bighorn Sheep Population.

Infectious pneumonia associated with the bacterial pathogen is an impediment to bighorn sheep () population recovery throughout western North America, yet the full range of virulence in bighorn sheep is not well-understood. Here, we present data from an introduction event in the Zion desert bighorn sheep () population in southern Utah. The ensuing disease event exhibited epidemiology distinct from what has been reported elsewhere, with virtually no mortality (0 adult mortalities among 70 animals tracked over 118 animal-years; 1 lamb mortality among 40 lambs tracked through weaning in the two summers following introduction; and lamb:ewe ratios of 34.