|Knowles, Donald - Don|
Submitted to: Clinical and Vaccine Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2011
Publication Date: 5/25/2011
Publication URL: http://cvi.asm.org/content/18/7/1133.full
Citation: Herndon, C.N., Shanthalingam, S., Knowles Jr, D.P., Call, D.R., Srikumaran, S. 2011. Comparison of Passively Transferred Antibodies in Bighorn and Domestic Lambs Reveals One Factor in Differential Susceptibility of These Species to Mannheimia haemolytica-Induced Pneumonia. Clinical and Vaccine Immunology. (7):1133-8. Interpretive Summary: Pneumonia in bighorn sheep is a population limiting disease and an important issue for multiple use of Western rangelands. Comparatively domestic sheep are as a population resistant to bacteria which cause fatal pneumonia in bighorn sheep. A likely reason for the differential susceptibility between bighorn and domestic sheep is the lack of population immunity in bighorn sheep. This study showed that within the populations studied domestic sheep had significantly higher amounts of antibody to pneumonia causing bacterial components than bighorn sheep. Passively transferred immunity represent antibody within the colostrum of the mother that is transferred to the offspring through suckling of the newborn. Should this lack of anti-bacterial antibody within colostrum be widespread than it represents another significant comparative factor between domestic and bighorn sheep leading to the enhanced susceptibility of bighorn to bacterial caused fatal pneumonia.
Technical Abstract: Mannheimia haemolytica consistently causes fatal bronchopneumonia in bighorn sheep (BHS; Ovis canadensis) under natural and experimental conditions. Leukotoxin is the primary virulence factor of this organism. BHS are more susceptible to developing fatal pneumonia than the related species Ovis aries (domestic sheep [DS]). In BHS herds affected by pneumonia, lamb recruitment is severely impaired for years subsequent to an outbreak. We hypothesized that a lack of maternally derived antibodies (Abs) against M. haemolytica provides an immunologic basis for enhanced susceptibility of BH lambs to population-limiting pneumonia. Therefore, the objective of this study was to determine the titers of Abs directed against M. haemolytica in the sera of BH and domestic lambs at birth through 12 weeks of age. Results revealed that BH lambs had approximately 18-fold lower titers of Ab against surface antigens of M. haemolytica and approximately 20-fold lower titers of leukotoxin-neutralizing Abs than domestic lambs. The titers of leukotoxin-neutralizing Abs in the serum and colostrum samples of BH ewes were approximately 157- and 50-fold lower than those for domestic ewes, respectively. Comparatively, the higher titers of parainfluenza 3 virus-neutralizing Abs in the BH lambs ruled out the possibility that these BHS had an impaired ability to passively transfer Abs to their lambs. These results suggest that lower levels of leukotoxin-neutralizing Abs in the sera of BH ewes, and resultant low Ab titers in their lambs, may be a critical factor in the poor lamb recruitment in herds affected by pneumonia.