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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Ruminant Diseases and Immunology Research » Research » Research Project #432020

Research Project: Identification of Disease Mechanisms and Control Strategies for Bacterial Respiratory Pathogens in Ruminants

Location: Ruminant Diseases and Immunology Research

Project Number: 5030-32000-116-00-D
Project Type: In-House Appropriated

Start Date: Oct 1, 2016
End Date: Sep 30, 2021

Objective:
Objective 1. Define the virulence determinants and mechanisms involved with the principal bacteria associated with bovine respiratory disease, including identifying microbial mechanisms used by commensal bacteria to become pathogens, and identifying the mechanisms of bacterial colonization in target hosts. Subobjective 1.1: Identify microbial mechanisms used by commensal bacteria to become pathogens. Subobjective 1.2: Identify the mechanisms of bacterial colonization of the host. Objective 2. Determine the host-pathogen interactions associated with respiratory infections, including developing animal disease models to study respiratory disease complex, identifying the host factors that drive the early innate immune response to bacterial respiratory infections, and characterizing functional genomics of the host associated with respiratory infection. Subobjective 2.1. Continue the development of animal disease models to study respiratory disease complex. Subobjective 2.2. Identify the host factors that drive the early innate immune response to bacterial infection. Subobjective 2.3. Characterize functional genomics of the host associated with respiratory infection. Objective 3: Develop intervention strategies to reduce antibiotic use, including developing vaccines that will induce early mucosal immunity in young animals, and developing and evaluating immune-modulators to prevent and/or treat respiratory disease. Subobjective 3.1. Develop vaccines that induce early mucosal immunity in young animals. Subobjective 3.2. Develop and evaluate immune modulators to prevent and/or treat respiratory disease.

Approach:
Binding of bacteria to mucosal surfaces, and evasion of host innate and adaptive immunity are critical to successful colonization and maintenance of infection. Identification of key molecular players in these interactions should enable potentially effective intervention strategies. We will utilize a coordinated and multipronged approach to characterize molecular mechanisms promoting respiratory bacterial pathogen colonization, adherence, and persistence in cattle. We plan to use experimental ruminant models and specific mutants to describe molecular mechanisms enabling bacteria to colonize, adhere and grow in the respiratory tract, and to examine the influences of primary viral infection on secondary bacterial infections. While much knowledge has been gained regarding the individual pathogens involved in BRDC, less is known concerning co-infections involving bacterial and viral respiratory pathogens. Given the expertise of our research team, and specific etiologic agent prevalence in the field, we will focus on BVDV and BRSV as the viral pathogens, and Mannheimia haemolytica, Pasteurella multocida, Histophilus somni and Mycoplasma bovis as the bacterial agents. We plan to continue the development of reproducible models of viral predisposition to bacterial disease and to characterize the host and infectious agents’ response using a comprehensive approach. Bacterial genes or gene products identified in these studies will be used, based on their importance in colonization, for developing and testing novel vaccines. Furthermore, we will examine the potential of immunomodulators to enhance the host response to infection with respiratory pathogens. The overriding goal of this plan is to develop preventative measures that aid in the reduction or elimination of BRDC in beef and dairy cattle. Reductions in BRDC will be of substantial economic benefit to cattle producers. However, as specific bacterial pathogens involved in BRDC are significant causes of morbidity and mortality in wild ruminant populations, there are aspects of this research plan that include those species. For example, bighorn sheep suffer severe die-offs as a result of respiratory disease and it is considered the major factor impacting the long-term sustainability of bighorn sheep populations. Moreover, M. bovis has additionally emerged in North American bison, causing substantial economic losses to producers and threatening the stability of heritage herds. Therefore, strategies to reduce respiratory disease in wild ruminant populations will be of substantial value to the public interest in sustaining wildlife populations, as well as reduce economic losses to bison producers.