2017 ESA Annual Meeting (August 6 -- 11)

COS 108-7 - Immunity and connectivity influence response to a Mycoplasma ovipneumoniae outbreak in subpopulations of Mojave desert bighorn sheep

Wednesday, August 9, 2017: 3:40 PM
D137, Oregon Convention Center
Brian S. Dugovich1, Brian P. Dolan2, Brianna R. Beechler2, Ben J. Gonzalez3, Clinton W. Epps4 and Anna E. Jolles2, (1)Integrative Biology, Oregon State University, Corvallis, OR, (2)Biomedical Sciences, Oregon State University, Corvallis, OR, (3)California Department of Fish and Wildlife, Rancho Cordova, CA, (4)Fisheries and Wildlife, Oregon State University, Corvallis, OR
Background/Question/Methods

Infectious diseases may be key drivers in the extinction vortices of small, isolated wildlife populations due to the loss of immunogenetic heterozygosity. In 2013, an epizootic of Mycoplasma ovipneumoniae (M. ovi.) caused high mortality in desert bighorn sheep (DBH) at Old Dad Peak in the Mojave National Preserve, California and spread to neighboring subpopulations. Genetic diversity varies widely among subpopulations in this sys­tem, but the consequences of that diversity during an epizootic were unclear. We expected that less connected subpopulations would have a weaker immune response and have a higher prevalence of M. ovi. infection. The opposing view was that higher connectivity would facilitate infectious disease spread among the metapopulation. We used blood samples (n=72 in 2013, n=44 in 2014) from DBH captured in 13 populations to measure immunity using a variety of immu­noassays (hematology, bacterial killing, and lymphocyte proliferation). We evaluated whether those immune function measures were correlated with disease status or subpopulation connectivity.

Results/Conclusions

Our results showed significant differences in pair-wise immune response measures between subpopulations (p<0.05). Connectivity was negatively correlated with disease prevalence at the time of capture (p<0.001), and the bacterial killing ability of blood was positively correlated with an active M. ovi. infection (p<0.01). Therefore, DBH subpopulations demonstrated inherent immune response differences, and more connected subpopulations were able to resist M. ovi. invasion. DBH that were actively infected with M. ovi. had an upregulated innate immune response which aided in infection survival. These findings support management decisions that increase connectivity within a metapopulation, because increasing connectivity could reduce inbreeding and drift and increase disease resistance.