Identification of Mannheimia Haemolytica Shedding Dynamnics of Domestic Sheep under Range Conditions
Animal Diseases Research
2013 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. Documents SCA with U of ID.
This work related to objective 1 of parent project by the provision of genomic data supporting identification of low transmission genotypes. Nasal shedding of respiratory pathogens and other flora provide important evidence for transmission and for the competitive environment related to transmission of respiratory pathogens. Genome-wide association for nasal shedding of respiratory pathogens has been enhanced by the addition of high density (700,000+ element) sheep genotyping reagents. These reagents will allow genomic analysis at more than 10X the resolution of prior methods. Analysis of bacterial flora in the respiratory secretions of domestic sheep was delayed due to training of a replacement to fill a critical vacancy in USDA-ARS.