A new study in the Journal of Wildlife Diseases confirms, unequivocally, that the domestic sheep disease Mannheimia haemolytica kills bighorn sheep after the two species co-mingle. This paper has been rumored for the last several months and was cited in the recent Payette National Forest decision to close 60% of sheep grazing allotments on the Forest.
Surely this should end the discussion among reasonable people about whether science supports the notion that domestic sheep and bighorn sheep can co-exsist. They cannot and actions must be taken by Federal and State agencies to make sure that the two species do not overlap on the landscape.
ABSTRACT: Previous studies demonstrated that bighorn sheep (Ovis canadensis) died of pneumonia when commingled with domestic sheep (Ovis aries) but did not conclusively prove that the responsible pathogens were transmitted from domestic to bighorn sheep. The objective of this study was to determine, unambiguously, whether Mannheimia haemolytica can be transmitted from domestic to bighorn sheep when they commingle. Four isolates of M. haemolytica were obtained from the pharynx of two of four domestic sheep and tagged with a plasmid carrying the genes for green fluorescent protein (GFP) and ampicillin resistance (APR). Four domestic sheep, colonized with the tagged bacteria, were kept about 10 m apart from four bighorn sheep for 1 mo with no clinical signs of pneumonia observed in the bighorn sheep during that period. The domestic and bighorn sheep were then allowed to have fence-line contact for 2 mo. During that period, three bighorn sheep acquired the tagged bacteria from the domestic sheep. At the end of the 2 mo of fence-line contact, the animals were allowed to commingle. All four bighorn sheep died 2 days to 9 days following commingling. The lungs from all four bighorn sheep showed gross and histopathologic lesions characteristic of M. haemolytica pneumonia. Tagged M. haemolytica were isolated from all four bighorn sheep, as confirmed by growth in ampicillin-containing culture medium, PCR-amplification of genes encoding GFP and ApR, and immunofluorescent staining of GFP. These results unequivocally demonstrate transmission of M. haemolytica from domestic to bighorn sheep, resulting in pneumonia and death of bighorn sheep.
via TRANSMISSION OF MANNHEIMIA HAEMOLYTICA FROM DOMESTIC SHEEP (OVIS ARIES) TO BIGHORN SHEEP (OVIS CANADENSIS): UNEQUIVOCAL DEMONSTRATION WITH GREEN FLUORESCENT PROTEIN-TAGGED ORGANISMS — Lawrence et al. 46 (3): 706 — Journal of Wildlife Diseases.