Scott Raine on hunting, wildlife, and conservation

Home ] Articles ] About ] Photos ] Links ] [Eureka]

2008 Research Symposium

Respiratory Disease in Wild and Domestic Sheep

Boise, ID March 7-8, 2008

Promoted by Dr Glen Weiser, Caine Veterinary Lab, University of Idaho

4th in a series of workshops that started in May 2007 (Davis, Tucson, SLC, Boise)

·      Tone of the meeting was different from previous 3 meetings: cordial, sense of cooperation and collaboration among participants.

Format of the meeting:

Mix of speakers representing both state and federal agencies (both agriculture and wildlife), and universities, 1.5 days presentations, ending with a moderated round table discussion

Divided into three main sections:

A.  Overview of Disease, organisms, and population and stress factors

B.  Epidemiology and the “Respiratory Disease Complex”

C.  Environmental and Management Factors

DVD available:


A.  Overview of Disease, organisms, and population and stress factors

·      Dr Rink: Described how many bighorn sheep die-offs unfolded in Nevada were characteristic of a naive population being exposed to a novel ‘exogenous’ agent and while the exact mechanism wasn’t clear, it appeared that die-offs were a result of bighorns coming into contact with an infectious agent they had not experienced previously. She discussed how her focus is now on developing studies to further examine potential transmission from domestic sheep to wild sheep and, in conjunction with NDOW, establish a comprehensive baseline of disease prevalence in BHS source populations.

o     She highlighted the recently signed MoA between NDOW, NDOA and UNR.

·      Suggested that the question was not ‘if’ we should prevent contact, but ‘how’. Some of her suggestions included

o     Coordinate grazing dates to minimize contact between wild and domestic sheep during breeding seasons

o     Maintain male-only domestic sheep operations in moderate-risk allotments to reduce chances for contact with roaming young bighorn rams

o     Encourage trucking vs. trailing when moving domestic sheep to and from grazing allotments

o     Regular counting of domestic sheep to minimize possibilities of strays

o     Utilize guardian dogs

·      Dr. Karen Rudolf described several of the findings in a study from Hells Canyon during which nearly 100 bighorn sheep were monitored during a 6-month period following a major respiratory disease die-off.

o     Her conclusions were that the outbreak resulted from a complex of factors, including stress. While all the animals died of bacterial pneumonia (Pasteurella and Mycoplasma isolated) she felt that stress factors such as rut, climate and nutrition are areas we need to look at more closely in future die-offs.

·      4 well-known scientists then made presentations on current research:

o     Dr Srikumaran (WSU) – Mannheimia haemolytica produces a toxin (leukotoxin) that is non-pathogenic to domestic sheep but is highly lethal to bighorn sheep. He is currently developing a specific marker that will allow precise documentation of the transfer of organisms from domestic sheep to bighorn sheep.

o     Dr Briggs (USDA/ARS) – transferring technology developed in cattle for use in wildlife, essentially showing that bighorn sheep, like cattle, if orally exposed to modified respiratory pathogens for a period of weeks develop a resistance to subsequent virulent lung challenge. Implication is that it may be possible to develop a self-transmitting oral vaccine against Pasteurellosis in bighorn sheep.

o     Dr Bill Foreyt (WSU) – described original co-pasturing studies that demonstrated transmission of pathogens between domestic and bighorn sheep. His opinion was that the most likely solution, in the long term, would involve the production of a suitable vaccine for bighorn sheep (so far unsuccessful). Conclusions:

§      When domestic and bighorn sheep have close contact, the probability of the bighorns dying is very high

§      There are strains of bacteria carried by healthy domestic sheep that are lethal in bighorn sheep

§      Bighorn sheep are very susceptible to pneumonia compared to other species studied

o     Dr Tom Besser (WSU) – discussed his research on Mycoplasma  ovipneumoniae and the potential for this to be a primary agent responsible for pneumonia outbreaks in bighorn sheep. Predisposes animals to Pasteurella infection by adhering to the cilia and preventing mucociliary clearance. These are bacteria found in domestic sheep and goats, mouflon, bighorn and thinhorn sheep so theoretically any of these could be a source. Examples: Hells Canyon, Montana, Nevada. 

B.  Epidemiology and the “Respiratory Disease Complex”

·      Dr Mike Miller (Colorado Div Wildlife) – discussed the importance of environmental stressors and the fact that stress and cortisol levels in bighorns may play a role in development of respiratory disease. He pointed out that this does not diminish the need for management strategies intended to prevent novel pathogen introduction into susceptible herds.

o     Second presentation suggested that we spend less time, energy and resources in responding to events and trying to solve the puzzle and put more of our efforts into identifying risk factors that can be managed to reduce the probability of epizootics from occurring…e.g. effective separation.

·      Dr Frances Cassirer (Idaho Fish and Game) – described the dynamics of pneumonia in Hells Canyon bighorn sheep. She found that pneumonia was the most common cause (43%) of adult mortality and the primary factor limiting population growth. Cougar predation was the second most common known cause (27%) in adults but it did not reduce rate of population growth significantly. Pneumonia was the most common cause of lamb mortality (86%) and pneumonia-related mortality was detected whenever summer lamb survival was <50%. Pneumonia mortality rates in lambs were high from days 21-91 days of age and peaked at 42-70 days of age. Interestingly, no correlation between high population densities and respiratory disease outbreaks was found. Her feeling was that when densities are high, we just have a greater chance of detecting mortalities (differentiation between detection and cause & effect).

·        Dr Mark Drew (Idaho Fish and Game) – discussed the protocol IFG use for assessing health of bighorn sheep when captured for population assessment or translocation (>1,500 bighorn sheep between 1988 and 2007). He presented summaries of their findings and some basic trend analysis.

·      Letizia Tomassini (UC Davis) – presented an ecological study comparing the distribution of Pasteurella trehalosi and Mannheimia haemolytica between Sierra Nevada Bighorn sheep, White Mountain bighorn sheep and domestic sheep.

·      Becky Frey (USDA) discussed herd health and habitat quality in relationship to Pasteurella spp.-induced pneumonia in bighorn sheep. She suggested that virulence factors of Pasteurellaceae and selenium, important in immune function, were critical factors to consider when identifying conditions favoring a pneumonic epizootic.

C    Environmental and Management Factors

·      Dr Dale Toweill (Idaho Fish and Game) - discussed the history and management (especially restoration) of bighorn sheep in Idaho: currently focused on avoiding conflicts with domestic sheep by achieving geographical separation between the two species and working closely with the federal land management agencies and tribes to restore biodiversity and native species on public and tribal land (as directed by Congress).

·      Dr Mark Drew (Idaho Fish and Game) – discussed the considerations and procedures employed during restoration efforts in Idaho. Considerations include: suitable habitat, predator densities, proximity to domestic livestock (especially sheep) and acceptance of local landowners. Cost of translocation calculated to be approx. $1,000/animal.

·      Dr Nancy East (UC Davis) – discussed the importance of public land grazing to sheep production in the western USA and how producers, and the sheep industry as a whole, are negatively impacted by the loss of summer grazing on public lands. She stressed the importance of integrated private and public land to the long-term viability of the industry.

·      Dr. Jim Logan (Wyoming Livestock Board) – discussed the efforts Wyoming has made over the past several years to resolve the conflicts that exist at the interface between bighorn sheep and domestic sheep through the creation of a Wyoming Bighorn/Domestic Sheep Interaction Working Group. This working group aims to maintain healthy bighorn sheep populations while sustaining an economically viable domestic sheep industry in Wyoming. Their primary areas of concern include:

o     Role, myths and science of interspecies disease transmission and bighorn sheep stressors: a review of the existing scientific literature on the subject and development of research agenda

o     Management of bighorn and domestic sheep habitat and the political will to manage that

o     Compatibility of bighorn sheep herds and an economically viable domestic sheep industry

o     Public perception and opinions of sheep, their management and the domestic sheep industry.


·      Ron Kay (Idaho Department of Agriculture) - discussed the rules and regulations pertaining to livestock management of public lands (BLM and USFS).

·      Kevin Hurley (Wyoming Game and Fish) – discussed the management of domestic sheep and domestic goats in wild sheep habitat in Wyoming and presented the WAFWA Wild Sheep Working Group (23 state, provincial, territorial agencies in Western US and Canada) recommendations upon which federal agencies should base their policies for managing these species in bighorn sheep habitats. He emphasized that recognition of the risk associated with contact between domestic sheep/goats and wild sheep is essential to long term management strategies, and to economic viability of federal land grazing permittees.

·      Dr. Glen Weiser (University of Idaho) – ended the conference with a presentation describing a brief history of taxonomy of Pasteurellacea implicated in sheep respiratory disease with the goal of reducing the confusion surrounding the current naming of these bacteria.

Final round-table discussion – general sense was one of ‘moving ahead’ and getting past prior conflicts and disagreements; there appeared to be a recognition that contact with domestic sheep does indeed pose a risk of disease transmission that can lead to bighorn sheep die-offs and that the most important question now is how do we all work together to minimize these risks; encouragement to engage in regular, open communication between sheep producers, wildlife managers and public land managers.


Contact Information:

Scott Raine
PO Box 812
Eureka, Nevada 89316


Copyright 2008, 2009, 2010, 2012, 2013 by Scott Raine
All Rights Reserved