Enteric Diseases of Swine and Cattle: Prevention, Control and Food Safety

NON-TECHNICAL SUMMARY: This project addresses critically important cross-cutting research areas and objectives that will enhance food safety while maintaining efficient pork and beef production by identifying and characterizing emerging and newly identified agents associated with enteric disease in cattle and swine with particular attention to those with zoonotic potential, developing interventions and preventative measures to reduce animal carriage and human transmission of the enteric zoonotic agents, includng development of new and improved vaccines and non-antibiotic therapies in order to prevent and treat enteric infections while reducing antibiotic usage and selective pressures for development of antibiotic resistance, and effectively disseminating information from the committee to possible users.

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APPROACH: <ol>
<li> Monitor pathogen genotypes to identiy trends in prevalence and to detect the emergence of new types and archive strains for comparison with future isolates and for historic assessment of prevalence of virulence determinants yet to be discovered, L. intracellularis. <li> MN will characterize virulence and pathogenic factos in the Lawsonia sequence identifiable by sequence homology, and clone and express potential pathogenic or immunogenic genes from Lawsonia in bacteria. Resultant recombinant proteins will be purified and evaluated for use in ELISAs, singly or in combination, in order to improve Lawsonia serologies used in veterinary diagnostic laboratories. In vitro and in vivo studies will be conducted by MN and SD to evaluate factors involved in infectivity of Lawsonia in cell cultures and germ-free pigs, respectively. Resultant models of proliferation will be used to evaluate the mechanism of proliferation of L. intracellularis-infected cells. <li> To meet continuing educational needs of NC-1007 members, interested students and colleagues, we also propose to sponsor a mini-symposium to be held in conjunction with the Conference of Research Workers in Animal Diseases </ul>
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PROGRESS: 2007/01 TO 2007/12<BR>
OUTPUTS: In vitro activity of six antimicrobial agents against ten L. intracellularis isolates from the U.S. and Europe. Lawsonia intracellularis is an obligate intracellular bacterium and the causative agent of proliferative enteropathy in pigs as well as a variety of other species. To achieve the best outcome for treatment and control of proliferative enteropathy, the selection of correct antimicrobials is a critical decision. However, little information on antimicrobial sensitivities against L. intracellularis is available because few strains have been successfully isolated worldwide. In this study, a tissue culture system was used to determine the minimum inhibitory concentrations of both intracellular and extracellular activity against 10 Lawsonia isolates from the United States (n=6) and Europe (n=4). Results of these in vitro studies can be used as a basis for evaluating treatment options in the field. Molecular epidemiologic typing of L. intracellularis. New knowledge regarding infection and transmission of L. intracellularis was obtained using the variable number tandem repeat (VNTR) genetic typing technique. Though Lawsonia is antigenically conserved, there is genetic variation that exists between isolates. No variation was observed between isolates obtained from various clinical types of proliferative enteropathy within a flow, including acute, chronic, and subclinical samples. Slight variation between isolates from different geographic locations was detected, though those variations were no greater between isolates from different continents than between isolates from different Midwestern U.S. pig farms. Marked variation exists, however, between isolates from pig and certain non-pig sources. These variations may be used to track outbreaks occurring in pigs, horses, or other animals. <BR>PARTICIPANTS: Connie Gebhart Suphot Wattanaphansak Richard Isaacson Randall Singer <BR>TARGET AUDIENCES: American Association of Swine Veterinarians International Pig Veterinary Society Leman Conference
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IMPACT: 2007/01 TO 2007/12<BR>
Proliferative enteropathy is an important infectious disease caused by the obligate intracellular bacterium, Lawsonia intracellularis. Information on the in vitro activity of six commonly used antimicrobial agents against ten L. intracellularis isolates can be used for evaluating treatment options in vivo. Development of a molecular typing database will enable further studies on the ecology and epidemiology of L. intracellularis.