Mycoplasma ovipneumonia was recently found in Bighorn sheep in Montana’s Missouri River Breaks. This is the first time pneumonia has been detected in area 622 of Montana which led to a sizable winter dieoff and the closure for hunting in the Hunt District. There are herds in Montana that have this type of pneumonia bacteria that have been doing okay for quite some time, which would suggest that herds infected long ago developed herd immunity to this bacteria.
However, this strain of M. Ovi bacteria has never been sequenced before in the labs. It’s just slightly different. So where did the bacteria come from? According to an FWP disease ecologist, domestic sheep and goats carry many variations that haven’t been documented in wild sheep.
We do know that the Browns’ ranch in the Breaks began grazing 500 domestic sheep and goats beginning in 2019. What was once a disease-free, isolated, sheep stronghold, is now in peril. Populations have been declining since 2019 with lamb recruitment down to 33 lambs per 100 ewes in 2022 and 2023, which is half of what they were producing from 2016-2021.
Another culprit adding to the decline of the sheep in the Breaks is the influx of mountain lions. Lions are occupying more of the Breaks now according to Region 6 Wildlife Manager Scott Thompson.
