RESEARCHERS say they could be on a path to developing new strategies to prevent pneumonia in feedlot cattle, after identifying unique proteins in the three groups of bacterial species commonly implicated with bovine respiratory disease.
The US study published in the science journal Genome, says the unique proteins, or antigens, were identified in the outer membrane of the BRD-causing bacteria, which they hope can be harnessed to protect the animal.
It is well understood that poor health, viruses, and environmental stress can leave young calves susceptible to secondary bacterial infections that cause bovine respiratory disease.
These severe infections commonly result in pneumonia, and a major cost to the industry.
The annual economic losses on the 14.5 million cattle in US feedlots are estimated at being between A$1 billion to A$1.2b.
BRD is also a big problem in Australia, costing the one million cattle-on-feed industry about $40 million a year.
To identify the unique proteins, scientists at the US Department of Agriculture's Agricultural Research Service studied the genetic material of multiple strains of three groups of bacterial species commonly implicated with BRD.
The researchers then sorted the variable genotypes of M. haemolytica into two strain types (type 1 and 2).
It is not uncommon to find all three groups of bacteria living in the upper respiratory tract of cattle with no signs of BRD, along with communities of 'good' bacteria. When a calve's immune system becomes weakened, the three bacteria (H. somni, P. multocida, and type 2 M. haemolytica) multiply in the upper respiratory tract and invade the lungs, where they cause disease.
But the researchers found this multiplication in calves with weakened immune systems did not happen as frequently with type 1 M. haemolytica.
"These antigens induce an immune response and can protect the animal," Dr Wynn said.
"We anticipate these proteins can be used in future preventative measures without disrupting other 'good' microorganisms coexisting within the same environment or host."
Dr Wynn said one of the most exciting discoveries was to find the outer membrane protein W, or OmpW, in all three harmful bacteria but not in the type 1 M. haemolytica.
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