Two Sheep Test Positive for Pneumonia-Causing Bacteria North Central Montana

Test results from two rams from bighorn sheep hunting district 622 have tested positive for a microorganism that can cause pneumonia. One of the sheep tested was harvested by a hunter this past fall. The second ram died during spring survey efforts by Montana Fish, Wildlife & Parks and had visible evidence of pneumonia in his lungs. Both rams tested positive for Mycoplasma ovipneumonia or M. ovi. M. ovi can facilitate infections by other bacteria, leading to pneumonia outbreaks in bighorn sheep herds. FWP has documented such outbreaks, and subsequent population declines in other bighorn sheep herds in Montana. “Pneumonia can cause all-age die-offs and chronic infections in adult and lamb bighorn sheep. This can persist for many years within a herd,” said Dr. Jennifer Ramsey, FWP wildlife veterinarian. “This situation is very complicated and not completely understood because we also have robust herds infected with M. ovi and other pneumonia-causing bacteria, and we do not see population impacts.” Although other respiratory tract bacteria have previously been found bighorn sheep in HD 622, M. ovi was not detected prior to detections in these two rams, despite ongoing health monitoring since 2016. FWP is continuing to look at the strain of M. ovi found in the rams to see if it offers further information about the infection. “This is disappointing news for this herd, which has been one of our strongest in recent years,” said FWP Region 6 supervisor Drew Henry. Earlier this month, the Montana Fish and Wildlife Commission closed bighorn sheep hunting in HD 622 due to a dramatic loss of population. HD 622 is located on the north side of the Missouri River Breaks in northeast Montana. Concerns over bighorn sheep populations in the hunting district have mounted over the past two years as biologists have noted a decline during aerial counts and in 2024 hunters noticed sick sheep and a decline in numbers within the hunting district. FWP will continue to monitor the few remaining sheep in the hunting district. Members of the public recreating in the area are encouraged report sheep sightings to the Glasgow FWP office at 228-3700.