Microorganisms Associated With a Pneumonic Epizootic in Rocky Mountain Bighorn Sheep (Ovis Canadensis Canadensis)

Abstract

A comprehensive study of a pneumonic epizootic was initiated when the first signs of disease were noted in a metapopulation of bighorn sheep inhabiting Hells Canyon, bordering Idaho, Oregon, and Washington. A total of 92 bighorn sheep were tested for etiologic agents during the following 6-mo study period. The study population included bighorn sheep believed to be the subpopulation in which disease was first noted, and these sheep were translocated to a holding facility in an effort to contain the disease (group A1, n = 72); bighorn sheep in other subpopulations (group A2) with evidence of clinical disease were captured, sampled, given antibiotics, and released (n = 8) and those that were found dead were necropsied (n = 12). Samples, including oropharyngeal and nasal swabs, and lung and liver tissue were collected from the bighorn sheep identified above. Tissue was collected at necropsy from 60 group A1 bighorn sheep that died following translocation, and samples were cultured for bacteria and viruses. Blood samples were tested for antibodies against known respiratory viruses, and histopathology was conducted on tissue samples. The major cause of death in both group A1 and group A2 bighorn sheep was a rapidly developing fibrinous bronchopneumonia. Multiple biovariants of Pasteurella were isolated from oropharyngeal and nasal samples from both groups, and Mycoplasma ovipneumonia was isolated from five group A1 oropharyngeal samples. Organisms isolated from lung tissue included Pasteurella multocida multocida a and Pasteurella trehalosi, both of which differentiated into multiple strains by restriction enzyme analysis, and parainfluenza-3 virus (PI-3). Paired serum samples revealed > fourfold increases in titers against PI-3 and bovine respiratory syncytial viruses. It was concluded that this epizootic resulted from a complex of factors including multiple potential respiratory pathogens, none of which were identified as a primary pathogen, and possible stress factors.

Comparison of Passively Transferred Antibodies in Bighorn and Domestic Lambs Reveals One Factor in Differential Susceptibility of These Species to Mannheimia haemolytica-Induced Pneumonia

“…5). We chose to determine PI-3-neutralizing titers because several BHS herds have been reported to test positively for anti-PI-3 Abs (26,29). Results from the virus neutralization assays revealed that the BHS serum and colostrum samples had high levels of PI-3-neutralizing Abs.…”

“…Outbreaks of bronchopneumonia in previously healthy populations of BHS often result in high death rates among all age groups initially, followed by years of impaired recruitment due to pneumonia in lambs (5,21,24,28). During these outbreaks, members of the genera Mannheimia, Bibersteinia, and Pasteurella, including Mannheimia (Pasteurella) haemolytica, Bibersteinia (Pasteurella) trehalosi, and Pasteurella multocida, have commonly been isolated from pneumonic lungs (16,26). Of these, M. haemolytica has consistently been shown to cause fatal bronchopneumonia in BHS under experimental conditions (9,12,20).…”

Subcutaneous Botryomycosis Due to Bibersteinia trehalosi in a Texas Longhorn Steer

“…Bibersteinia trehalosi causes septicemia in lambs and pneumonia in cattle, domestic sheep, and bighorn sheep in North America 8,18,22,26 but, to our knowledge, has not been reported as a cause of botryomycosis. The purpose of this report is to describe a case of subcutaneous botryomycosis caused by B. trehalosi in a Texas Longhorn steer.…”

Detection of Mycoplasma ovipneumoniae and M. arginini in Bighorn Sheep Using Enrichment Culture Coupled with Genus- and Species-Specific Polymerase Chain Reaction

“…They may act alone or in concert with other agents associated with pneumonia in bighorn sheep (Miller, 2001;Rudolph et al, 2003Rudolph et al, , 2007. Mycoplasma ovipneumoniae infections have been associated with chronic respiratory infections, poor growth, and exercise intolerance of lambs in domestic sheep herds (Sullivan et al, 1973;Timoney et al, 1988) and have been suggested as a possible cause of population-limiting pneumonia in bighorn sheep adults and lambs (Besser et al, 2008).…”

“…All cultures, with one exception, were PCR positive for M. arginini, and no animal was culture negative and PCR positive for M. arginini. Although M. arginini and M. ovipneumoniae are most frequently detected in bighorn sheep (Rudolph et al, 2007;Besser et al, 2008), the genus primers used in this study allow for the detection of additional species. Cultures of any Mycoplasma species also would be useful in strain typing and virulence factor studies.…”