The first report of a sick and coughing bighorn was reported in early May this year very near to the community of Joshua Tree, CA. For a while, only occasional reports were received of sick animals ranging from Fortynine Palms Canyon to the Maze Loop area. However, in mid-August, a dead lamb was found in the park and sent to a disease lab for necropsy.
Results of laboratory analysis of blood and tissue samples showed that this animal was infected with pneumonia. In other instances, the mortality rate for animals infected with the disease has been 50 to 90 percent, and there is no vaccine or cure. At this time it is unknown what mortality will be among Joshua Tree's herds. This form of pneumonia is not transmissible to humans.
The disease may enter into a wild population from domestic sheep or goats. Biologists caution the public to avoid releasing domestic sheep or goats into the wild as they often are disease carriers even if they have no symptoms. Desert bighorn often have no natural defenses to diseases carried by domestic animals.
That lack of natural resistance may result in high infection and death rates in bighorn populations. The few animals that survive may become carriers, infecting new lambs that often die within a few months of birth. An outbreak such as this one typically causes a long term decline in the population that can last for more than a decade.
Biologists have formed an interagency group to monitor disease outbreaks, suggest best practices for limiting effects of the disease, and provide recommendations for management actions. Members of the group represent the California Department of Fish and Wildlife, Nevada Department of Wildlife, National Park Service, and many affiliated researchers from the USGS and Oregon State University.