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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)
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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:
www.cainecenter.uidaho.edu/wildlife.htm
Highlights:
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
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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.
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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”
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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
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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
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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.
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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.
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