Cassirer, F., Manlove, K., Almberg E., Kamath P., Cox M., Wolff P., Roug, A., Shannon J.; Robinson R., Harris R., Plowright R.K., Hudson P., Cross P., Dobson A., Besser T. 2017. Management of pneumonia in bighorn sheep: risk, reservoirs, and resilience. Journal of Wildlife Management. doi:10.1002/jwmg.21309.
The potential risk posed by respiratory pathogens carried by domestic goats has long been uncertain. On the one hand, domestic goats frequently carry Mycoplasma ovipneumoniae, considered the primary agent of bighorn sheep pneumonia. However, on the other hand, previous comingling studies between domestic goats and bighorn sheep did not result in epizootic bighorn fatal pneumonia. This paper describes comingling of domestic goat carriers of M. ovipneumoniae with susceptible bighorn sheep, resulting in in epizootic transmission of the pathogen and development of pneumonia in all bighorn sheep. However, the character of the pneumonia was distinctly mild and all bighorn sheep recovered or were recovering by 100 days after commingling. Our working hypothesis is that domestic goat strains of M. ovipneumoniae, which are members of a distinct clade from strains carried by domestic sheep (See Cassirer et al., Evidence for strain specific immunity…), are sometimes (perhaps usually) associated with lower virulence and less persistence in bighorn sheep.
Manlove K., , E. F. Cassirer, P. C. Cross, R. K. Plowright, P. J. Hudson. Disease introduction is associated with a phase transition in bighorn sheep demographics. 2016. Ecology. DOI:10.1002/ecy.1520.
Proceedings of the Royal Society B published a paper led by consortium member Kezia Manlove describing the role of population substructuring on pneumonia transmission. The analysis suggests that pneumonia transmission among lambs is localized into particular ewe groups. Furthermore, the number of groups, but not group size, changes with population size. This suggests that pneumonia transmission may persist, even as disease drives population sizes downwards. Contact Kezia Manlove (firstname.lastname@example.org) for a copy.
PLOS ONE published a paper detailing results from experiments conducted by consortium members Tom Besser and Frances Cassirer (October 2014): "Epizootic Pneumonia of Bighorn Sheep following Experimental Exposure to Mycoplasma ovipneumoniae". Tom, Frances, and their collaborators at Washington State demonstrated pen-to-pen transmission of M. ovipneumoniae after experimental inoculation of bighorn sheep. They also show that the pathology and time-course of infection with lab induced M. ovipneumoniae closely resembles that observed in the field.
PLOS ONE published a paper led by consortium member Raina Plowright (April 2013) examining the relationship between previous exposure to pneumonia and subsequent immunity and survival. Our analyses show that surviving ewes develop immunity to pneumonia but do not effectively pass immunity to their lambs. This suggests that pneumonia in bighorn sheep will lead to aging populations and insufficient numbers of lambs to maintain healthy populations.
The Journal of Animal Ecology published a paper (February 2013) led by Frances Cassirer, and other consortium members, describing pneumonia dynamics in Hells Canyon. The paper describes four age categories of pneumonia in bighorn sheep and shows that adults are most likely to die of pneumonia in winter, while lambs are more likely to die of pneumonia within a short period in summer. Contact Frances Cassirer for a copy (email@example.com).