Date of Award
Doctor of Philosophy
Veterinary Microbiology and Preventive Medicine
Max F. Rothschild
D. L. Harris
Resistance of Chinese pigs (n = 289) to the K88ac+ Escherichia coli-mediated disease was determined by in vitro brush border membrane adherence assay, Meishan pigs were highly resistant (nonadherent). Minzhu pigs of susceptible and resistant phenotypes were identified in ratios consistent with a one-locus gene model (frequency of susceptibility at 8%). Inheritance within the Fengjing breed was unclear as a weak adherent phenotype and resistant phenotype were identified;A non-invasive antemortem method to phenotype pigs has been unavailable. Milk from 17 susceptible and 17 resistant sows was used to test the feasibility of an agglutination assay based on interaction of K88 bacteria mixed with milk fat globules. The difference between resistant and susceptible samples was significant at P < 0.0001. Phenotypes were determined based on the percent light transmission passed through sample mixtures. Assays comparing samples from resistant, susceptible, and weak adherent sows produced percentages in different ranges. Substitution of pilus antigens for bacteria was successful. Repetition of assays of samples of the three phenotypes were highly accurate;Phenotyped or retrospectively genotyped Chinese dams and sires were bred to produce litters for clinical study and correlation to in vitro phenotypes. Piglets (n = 23) of resistant, susceptible, and weak adherent phenotypes were inoculated with K88+ E. coli. Control pigs (n = 18) were challenged with a plasmid deleted K88-strain. Pigs received sterile serum for hydration and were inoculated within 5 hours of birth. Pigs were euthanized and necropsied 18 hours post inoculation. Weights and clinical scores for depression, dehydration, and diarrhea were recorded. Intestine samples were evaluated for histopathology and bacterial colony forming units/ml. Pigs of the resistant phenotype and controls did not develop disease signs or symptoms. Susceptible pigs developed diarrhea and depression and were dehydrated. Pigs of the weak adherent phenotype developed diarrhea but were more alert and responsive and less dehydrated than piglets of the traditional susceptible phenotype.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Rita Diane Michaels
Michaels, Rita Diane, "Innate genetic resistance to K88+ Escherichia coli-mediated diarrheal disease in Chinese Meishan, Fengjing, and Minzhu pigs " (1998). Retrospective Theses and Dissertations. 11634.