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1 July 2016 Fusobacterium necrophorum in North American Bighorn Sheep ( Ovis canadensis) Pneumonia
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Fusobacterium necrophorum has been detected in pneumonic bighorn sheep (BHS; Ovis canadensis) lungs, in addition to the aerobic respiratory pathogens Mannheimia haemolytica, Bibersteinia trehalosi, Pasteurella multocida, and Mycoplasma ovipneumoniae. Similar to M. haemolytica, F. necrophorum produces a leukotoxin. Leukotoxin-induced lysis and degranulation of polymorphonuclear leukocytes (PMNs) and macrophages are responsible for acute inflammation and lung tissue damage characteristic of M. haemolytica-caused pneumonia. As one approach in elucidating the role of F. necrophorum in BHS pneumonia, we determined the frequency of the presence of F. necrophorum in archived pneumonic BHS lung tissues, and susceptibility of BHS leukocytes to F. necrophorum leukotoxin. A species-specific PCR assay detected F. necrophorum in 37% of pneumonic BHS lung tissues (total tested n=70). Sequences of PCR amplicons were similar to the less virulent F. necrophorum subsp. funduliforme. Fusobacterium necrophorum leukotoxin exhibited cytotoxicity to BHS PMNs and peripheral blood mononuclear cells. As with the M. haemolytica leukotoxin, F. necrophorum leukotoxin was more toxic to BHS PMNs than domestic sheep PMNs. It is likely that F. necrophorum enters the lungs after M. haemolytica and other aerobic respiratory pathogens enter the lungs and initiate tissue damage, thereby creating a microenvironment that is conducive for anaerobic bacterial growth. In summary, Fusobacterium leukotoxin is highly toxic for BHS leukocytes; however, based on the PCR findings, it is unlikely to play a direct role in the development of BHS pneumonia.

Sudarvili Shanthalingam, Sanjeevkumar Narayanan, Sai Arun Batra, Bavananthasivam Jegarubee, and Subramaniam Srikumaran " Fusobacterium necrophorum in North American Bighorn Sheep ( Ovis canadensis) Pneumonia," Journal of Wildlife Diseases 52(3), 616-620, (1 July 2016).
Received: 12 February 2015; Accepted: 1 October 2015; Published: 1 July 2016