Cough it Up: Bighorn Pneumonia

     Residents in the western portion of the United States would probably agree that they are very lucky for a number of reasons. The beautiful scenery, the history, and even coolest: the wildlife. One species in particular that is always incredible to get eyes on is the bighorn sheep. The bighorn sheep (Ovis canadensis) is a species of mountain sheep that are very well known for their incredible climbing abilities on steep, rocky mountains. At this time, it is considered to be a species of least concern according to the IUCN Red List with stable population trends.
The range of bighorn sheep throughout the Western US

An adult male ram bighorn sheep
An adult female ewe bighorn sheep


     One truly spectacular sight to see with bighorn sheep is the competition between rams for the attention and eventual mating with the ewes (female). This competition is displayed in the cover photo and it entails two rams running at each other at speeds of up to 20 miles per hour and crashing their heads together until one gives up. This doesn't always happen quickly though, in fact there have been documented cases of ram fights continuing for up to 24 hours! Unfortunately, this species and its populations are at risk for catching a particularly nasty disease called bighorn pneumonia.
     The Washington Dept. of Fish and Wildlife state that bighorn sheep are very susceptible to respiratory diseases, of which pneumonia is a top contender. The disease bighorn pneumonia is mostly associated with a bacterium called Mycoplasma ovipneumoniae. The interesting thing about this bacterium though, is it is also carried by domestic sheep with little to no obvious signs of disease. This is a problem though because that means the disease is very easily transmitted to the wild bighorn sheep who then display signs of the disease.
A deceased ram bighorn sheep that succumbed to bighorn pneumonia
     Common clinical signs noticed in diseased bighorn sheep include nasal discharge, coughing, respiratory distress, exercise intolerance, and general depression. The problem though, is that in most cases, diseased animals that are actively displaying these clinical signs are very hard to come by. Most bighorn sheep that are infected with pneumonia are generally found dead with very unique pathology discovered inside of the body during a necropsy. You can see photos of necropsied organs here. This is a unique disease too in that sometimes adult bighorn sheep can also become chronic bacterial carriers for the disease and inevitably spread the disease to other sheep in their flock. At this time there is no known vaccine for treatment for pneumonia in bighorn sheep.
     So what do we do here? What needs to change? Is there anything that can be changed or done to ensure that this problem stops happening? As of right now the current literature promotes euthanasia of any bighorn sheep populations that are discovered to have pneumonia in order to prevent the spread to other populations or to domestic flocks of sheep. A big concern that many people have though is the effect that ranching on these public lands has on the spread of pneumonia. As stated before, the disease is spread to wild bighorn populations via each other but also from domestic sheep to wild bighorn sheep. So, careful and proper ranching management is required in order to prevent the continuing spread of the disease from domestic to wild populations.
     As I've said before, as biologists, a main aspect of our job is to conserve and protect this planet as best we can. Sometimes this can be difficult as we need to make sure we're listening to our stakeholders (ranchers, hunters, fishers) along with lawmakers and they may have differing opinions for how things need to be done. It is a careful balance and it is something that is learned but with no easy answer. As we often learn in any human dimensions course, wildlife ecology is 80% people management and 20% wildlife management. Thank you all for reading and please see below for other articles and interesting reads! Keep an eye out next week for a guest post by Heather Kopsco, a Ph.D. Candidate from the University of Rhode Island as I will be on vacation.


Works Cited:

About Pneumonia, Bighorn Sheep Disease Research Consortium: http://bighornhealth.org/about-pneumonia

Maughan, R. 2015. Just north of Yellowstone, bighorn fall to pneumonia. The Wildlife News. https://www.thewildlifenews.com/2015/03/27/just-north-of-yellowstone-bighorn-fall-to-pneumonia/

Bighorn Sheep Pneumonia, National Park Service, U.S. Dept. of the Interior, March 29, 2018
https://www.nps.gov/articles/bhs-pneumonia.htm

Manlove KR, Cassirer EF, Cross PC, Plowright RK, Hudson PJ. 2014 Costs and benefits of group living with disease: a case study of pneumonia in bighorn lambs (Ovis canadensis). Proc. R. Soc. B 281:1-8

Other good reads:
For an interesting animation showing the spread of pneumonia in the Western US, please follow this link. 

For more photos detailing the pathology of bighorn pneumonia, follow this link.

If you're interested in reading other scientific publications on bighorn pneumonia, follow this link.
   












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