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

NON-TECHNICAL SUMMARY: The long-range goals of this Multistate Research Project are to: 1) obtain basic information on pathogenic mechanisms used by microorganisms that cause diarrheal disease in food animals and humans, 2) develop more effective vaccines and intervention strategies against intestinal pathogens, and 3) disseminate relevant information on food-borne pathogens to stakeholders. Viruses associated with the intestinal tracts of pigs and cattle isolated from fecal samples and waste lagoons will be characterized with respect to their specific animal host, surface proteins that mediate interactions with specific animal species, and their capacity to interact with different types of cells. Enteric bacteria associated with diarrheal disease bind to intestinal cells followed by growth and colonization of the intestines. It will be determined how extracellular proteins called enterotoxins produced by the bacteria facilitate colonization in piglets. Vaccines will be developed in order to reduce the carrier level of E. coli O157:H7 in the large intestine of cattle. Intervention strategies to be developed will: 1) reduce transmission of between pig farms in different geographical regions of the Midwest (Lawsonia intracellularis), 2) block colonization of chicken intestines (Camplobacter jejuni), 3) provide a better understanding of the complex host parasite relationship of a re-emerging pathogen of pigs (Brachyspira spp), and 4) determine the therapeutic efficacy of receptor analogues of host cell surface molecules against viruses and protozoa.

<P>APPROACH: Bovine and porcine enteric calcivirus isolates from fecal samples, waste lagoons and manure samples will be identified using RT-PCR and other techniques such as electron microscopy and ELISAs as needed. Also, environmental water sources and unprocessed foods will be screened for enteric viral pathogens and bacteria. The capacity of viral isolates to cause diarrhea and viremia will be determined and microarray analysis will be used assess gene expression during in vitro calciviral replication to identify pathways involved in virus adaptation to cell culture conditions. ABOH blood type antigens on bovine and porcine tissues will be characterized to assess binding of different calcivirus genotypes to these surface molecules. Fecal and nasal specimens will be screened for new strains of bovine-like toroviruses (BoTV) and bovine-like coronaviruses (BCoV). The interrelationships between genomic sequences of BoTV and BCoV, cross-protection, antigenic relatedness and tissue tropisms and host specificity will be determined. Intervention strategies for enteric pathogens will be developed using information obtained in the first Objective. The effect on diet on shedding of E. coli O157:H7 will be characterized in order to reduce prevalence and shedding. The role(s) of the heat-stable enterotoxins (EAST1 and STb) and heat-labile enterotoxin in binding and colonization of enterotoxigenic E. coli (ETEC) will be determined using a gnotobiotic piglet model. Attenuated live vaccines will be developed in an attempt to protect food animals against ETEC disease and reduce prevalence and shedding of E. coli O157:H7. Genetic typing will be used to study infection and transmission of Lawsonia intracellularis and new reagents will be developed for improved ELISAs. The role of a novel surface pilus in pathogenesis of Camplybacter jejuni will be studied by cloning and expression of the pilus gene. Pilus mutants will be tested for the capacity to adhere to epithelial cells and colonize neonatal chickens. Recent clinical isolates of Brachyspira spp. will be characterized with respect to: 1) antimicrobial sensitivity, 2) identification techniques, and 3) determination of the genomic sequence. In addition to development of improved traditional vaccines against enteric viruses, receptor mimic molecules designed to block binding of viruses to their cellular receptors will be tested as therapeutic agents. Similar studies using receptor mimics will be performed in attempt to block binding and colonization of newborn calves by Cryptospiridium parvum. The education component of the proposal described in Objective 3 will provide the following: 1) training for undergraduates and graduate students, 2) information to livestock producers and other professionals associated with food animal production and health, 3) knowledge to station representatives and collaborating scientists, and 4) scientific exchanges at both national and international levels. The Fourth International Rushmore Conference on Enteric Diseases will held in Rapid City, SD in the fall of 2010 or 2011.