Identification of Mannheimia Haemolytica Shedding Dynamnics of Domestic Sheep under Range Conditions
Animal Diseases Research
2012 Annual Report
1a.Objectives (from AD-416):
Develop effective strategies for limiting or eliminating the shedding of respiratory pathogens from domestic sheep under range conditions. Data clearly shows that Mannheimia Haemolytica strain A2, found in domestic and bighorn sheep can lead to population limiting pneumonia is bighorn sheep and economic losses in domestic sheep. Working collaboratively with the University of Idaho and the United States Sheep Experiment station the pattern of respiratory pathogen shedding including M. haemolytica will be identified under different seasonal and management range conditions. Domestic sheep identified as “shedders” will be used to test methods such as completive inhibition to limit or eliminate pathogen shedding.
1b.Approach (from AD-416):
The conditions and level(s) of M. haemolytica shedding from domestic sheep is a critical issue for the development of policy concerning the grazing of domestic sheep under range condtions, especially where there is potential contact with bighorn sheep. Nasal swabs will be collected from 125 domestic sheep under three different seasonal and/or range conditions at the USSES. Such samples will be sent to the microbiological laboratory at Caine Center, the University of Idaho. Samples will be processed for the presence and level of M. haemolytica and Mycoplasma species. At the completion of sampling (three samplings per year for 3 years) “high” shedding and “low” shedding sheep will be identified and transported to ARS laboratory in Pullman, WA. These sheep will be treated with leukotoxin free Bibersteinia trehalosi which has been shown to inhibit M. haemolytica by contact dependent inhibition. Treated sheep will then be tested for their ability to shed M. haemolytica.
This work relates to objective 1 of parent project by the provision of genomic data supporting identification of low transmission genotypes. Initial RNA sample collection was begun for an RNA-Seq experiment that will examine host-pathogen interactions in domestic and bighorn sheep. Sequence data from RNA of domestic sheep were collected to provide baseline RNA expression profiles for comparison. Once complete, this experiment will provide detailed evidence of genes and genetic pathways differentially activated in response to leukotoxin from M. haemolytica. The first study to quantify a broad range of bacteria in nasal secretions of domestic sheep under range conditions is ongoing. Analysis of bacterial flora in the respiratory secretions of domestic sheep was delayed due to a critical vacancy in USDA-ARS. The project is ongoing and a manuscript is anticipated in the next year.