Management Implications of Our Research
One of the main motivations for our research is to provide information that can ultimately be applied to resolving the problem of pneumonia in bighorn sheep. We are still working on understanding the dynamics of this disease, however, which means the implications of our research for management are mostly a work in progress. Still, some of the information we have gathered so far is relevant to management.
What causes pneumonia in bighorn sheep?
There is good evidence that the bacterium Mycoplasma ovipneumoniae (M. ovi) predisposes bighorn sheep to pneumonia. Once a bighorn is infected with M. ovi, bacteria that normally live in its nose, throat, or gut can descend into the lungs and cause pneumonia. Ultimately, many different bacteria cause pneumonia, but most of these bacteria are usually harmless and would not cause disease without M. ovi first predisposing bighorn sheep to lung infections.
What does the fact that multiple bacteria, in the presence of M. ovi, can cause pneumonia mean for treatment?
The issue of multiple bacteria causing the disease contributes to the difficulty of developing an effective treatment for bighorn sheep pneumonia. M. ovi, like most mycoplasma species, is very hard to eliminate from the body. The fact that so many other microbes may be involved also complicates delivering treatment for this disease. A variety of antibiotics have been tried in the face of bighorn pneumonia outbreaks, with little success.
What tools are available right now to prevent bighorn sheep pneumonia?
Since there is no effective vaccine against bighorn sheep pneumonia at this time, and no effective treatments, the most important tool that wildlife managers have is prevention of contact between bighorn sheep and domestic sheep. This prevention measure is based on strong scientific evidence that when bighorn and domestic sheep come into direct contact, pneumonia outbreaks frequently occur in bighorn sheep. The Western Association of Fish and Wildlife Agencies issued a report in 2012 containing recommendations for managing domestic sheep in bighorn sheep habitats.
If a bighorn sheep survives a pneumonia epidemic, is that animal immune to future outbreaks?
Yes and no. Animals that survive an epidemic develop immunity that protects them from disease, but a few animals become carriers, which means they still harbor M. ovi in their systems. Carrier ewes can infect their lambs, and we suspect that such an event can trigger an epidemic among all lambs, leading to an outbreak of pneumonia that can kill many, or sometimes all, of the lambs. Outbreaks of pneumonia in lambs can occur sporadically or annually and continue for years to decades after the initial all-age epidemic. Unfortunately, we do not yet know what causes some individuals to become carriers, or how to easily identify them.
Will adding more sheep to a population that has had a pneumonia outbreak help the population recover?
Probably not. Naïve animals translocated into or near infected populations can become infected with M. ovi if they have contact with carriers or with actively shedding sick animals. Lambs of translocated ewes that survive M.ovi infection do not fare any better than lambs of resident ewes.
How long does pneumonia stay in a population that has been infected?
It appears that populations can stay infected with M. ovi for variable periods, ranging from a few years to more than a decade. Why this amount of time populations remain infected is so highly variable is a major focus of our research. If we can understand the factors that lead to some populations recovering quickly, we may be able to devise interventions to help infected populations recover more quickly.
The most important tool that wildlife managers have is prevention of contact between bighorn sheep and domestic sheep.