|Duff, Glenn - NEW MEXICO STATE UNIV.,NM|
Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 16, 2002
Publication Date: May 20, 2003
Citation: FRANK, G.H., BRIGGS, R.E., DUFF, G.C., HURD, H.S. EFFECTS OF INTRANASAL EXPOSURE TO LEUKOTOXIN-DEFICIENT MANNHEIMIA HAEMOLYTICA AT THE TIME OF ARRIVAL AT THE FEEDYARD ON THE SUBSEQUENT ISOLATION OF M. HAEMOLYTICA FROM NASAL SECRETIONS OF CALVES. AMERICAN JOURNAL OF VETERINARY RESEARCH. 2003. v. 64(5). p. 580-585. Interpretive Summary: Pneumonia in cattle costs the U. S. cattle industry approximately $1 billion in losses each year. Mannheimia haemolytica (MH) is a bacterial pathogen that is the major cause of acute pneumonia in cattle. Acute pneumonia usually occurs within the first week of arrival at the feedyard. Calves exposed intranasally to live MH that lack the ability to produce a toxin that destroys leukocytes were protected from colonization by the disease-causing wild-type MH. Since colonization is a pre-requisite for the development of pneumonia, inhibition of colonization is a desirable goal to seek in order to prevent pneumonia.
Technical Abstract: This experiment was to determine the effect of intranasal exposure on arrival at the feedyard of beef calves to a live leukotoxin-deficient Mannheimia haemolytica (lktA-deficient MH) on colonization by wild-type MH. Two groups of calves (from Arkansas and New Mexico) were used. Arkansas calves (n = 100, average 205 kg) were purchased from an order buyer barn. New Mexico calves (n = 100, average 188 kg) were obtained from one ranch. Calves were transported to a feedyard where half of each group was exposed intranasally with lktA-deficient MH upon arrival (exposed calves). Calves were observed daily for respiratory tract disease (RTD), and nasal swabs were collected periodically to determine their colonization status with MH. Serums were assayed for antibody to MH. At least 15 Arkansas calves were colonized with wild-type MH at the order buyer barn, whereas none of the New Mexico calves were colonized at the ranch. Intranasal exposure with lktA-deficient MH (exposure) on arrival elicited an increase in serum antibody titers to MH in the New Mexico calves, but titers were less in those treated for RTD. Exposure of the New Mexico calves offered protection from colonization by wild-type MH. Exposure elicited an increase in serum antibody titers to MH and reduced the incidence of colonization by wild-type MH. It is likely that an earlier exposure would allow an immune response to develop before calves were transported to a feedyard and offer protection from colonization and pneumonia caused by wild-type MH.