|Straus, David - TEXAS TECH UNIVERSITY|
|Loan, Raymond - TEXAS A&M UNIVERSITY|
Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 4, 1998
Publication Date: N/A
Interpretive Summary: Bovine respiratory disease (BRD) cost the feedyard producers at least 600,000,000 dollars a year because of acute sickness, chronic illness, and death loss. This disease is induced by a complex of stress, viral, and bacterial infections. The main bacteria involved in this disease is Pasteurella haemolytica and its mechanisms of producing disease is not well lunderstood. Pasteurella haemolytica ability to produce the neuraminidase enzyme while infecting stressed calves may be important in the bacterias ability to increase rapidly in the respiratory tract and induce disease.
Technical Abstract: Pasteurella haemolytica (Ph) is the most important cause of the bovine acute fibrinohemorrhagic pneumonia that occurs in market stressed calves following shipment to feedyards. Recent characterization of neuraminidase production by these organisms has shown that all 16 serotypes produce an immunologically similar form of the enzyme. Anti-neuraminidase antibody against PhA1 and PhA6 was determined in 101 two- to five- month old calves on their farms of origin, at the order buyer barn (OBB) and through 28 days in the feedyard. Half of the calves were vaccinated with a killed Ph serotype-A1 (PhA1) product. Nasal secretion and tonsil wash specimens were cultured for Ph and Pasteurella multocida(Pm). Serum antibody against PhA1 and PhA6 was measured by indirect hemagglutination (IHA) and anti-neuraminidase antibody was determined by the neutralization assay. At the feedyard, 73 calves had respiratory tract disease. IHA values ranged between 1:2 and 1:1024 for PhA1 and between 1:2 and 1:512 for Ph serotype A6 (PhA6). Forty-two, 24, and 28% of the calves were infected with PhA1, PhA6, and Pm, respectively. Ninety-six percent of the calves experienced an increase in anti-PhA1 neuraminidase antibody when sera drawn on feedyard day 28 was compared to sera drawn on the farm. These data demonstrate that the enzyme neuraminidase is produced in vivo in market stressed cattle following a natural Ph infection.