Mycoplasma ovipneumoniae can predispose bighorn sheep to fatal Mannheimia haemolytica pneumonia.
Mycoplasma ovipneumoniae has been isolated from the lungs of pneumonic bighorn sheep (BHS). However experimental reproduction of fatal pneumonia in BHS with M. ovipneumoniae was not successful. Therefore the specific role, if any, of M. ovipneumoniae in BHS pneumonia is unclear. The objective of this study was to determine whether M. ovipneumoniae alone causes fatal pneumonia in BHS, or predisposes them to infection by Mannheimia haemolytica. We chose M. haemolytica for this study because of its isolation from pneumonic BHS, and its consistent ability to cause fatal pneumonia under experimental conditions. Since in vitro culture could attenuate virulence of M. ovipneumoniae, we used ceftiofur-treated lung homogenates from pneumonic BHS lambs or nasopharyngeal washings from M. ovipneumoniae-positive domestic sheep (DS) as the source of M. ovipneumoniae. Two adult BHS were inoculated intranasally with lung homogenates while two others received nasopharyngeal washings from DS. All BHS developed clinical signs of respiratory infection, but only one BHS died. The dead BHS had carried leukotoxin-positive M. haemolytica in the nasopharynx before the onset of this study. It is likely that M. ovipneumoniae colonization predisposed this BHS to fatal infection with the M. haemolytica already present in this animal. The remaining three BHS developed pneumonia and died 1-5 days following intranasal inoculation with M. haemolytica. On necropsy, lungs of all four BHS showed lesions characteristic of bronchopneumonia. M. haemolytica and M. ovipneumoniae were isolated from the lungs. These results suggest that M. ovipneumoniae alone may not cause fatal pneumonia in BHS, but can predispose them to fatal pneumonia due to M. haemolytica infection.
Dassanayake
Rohana P
RP
Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-6610, USA.
Shanthalingam
Sudarvili
S
Herndon
Caroline N
CN
Subramaniam
Renuka
R
Lawrence
Paulraj K
PK
Bavananthasivam
Jegarubee
J
Cassirer
E Frances
EF
Haldorson
Gary J
GJ
Foreyt
William J
WJ
Rurangirwa
Fred R
FR
Knowles
Donald P
DP
Besser
Thomas E
TE
Srikumaran
Subramaniam
S
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D006651:Histocytochemistry / Q000662:veterinary; D008168:Lung / Q000276:immunology / Q000382:microbiology; D016978:Mannheimia haemolytica / Q000235:genetics / Q000276:immunology*; D045802:Mycoplasma ovipneumoniae / Q000235:genetics / Q000276:immunology*; D009500:Neutralization Tests / Q000662:veterinary; D012766:Pasteurellosis, Pneumonic / Q000276:immunology / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000662:veterinary*; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology / Q000382:microbiology*; D034581:Sheep, Bighorn
D000907:Antibodies, Bacterial; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S