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Assessment Of Risk Associated With The Minnesota Proposed Plan For Split-State Status For Mycobacterium Bovis (Bovine Tuberculosis)

Michigan Bovine Tuberculosis Bibliography and Database

In July 2005, a Minnesota beef herd tested positive for Mycobacterium bovis (M. bovis) and was officially declared infected with bovine tuberculosis (TB). This was the first infected herd identified since Minnesota’s Accredited Free (AF) status was obtained in 1976. Subsequent testing identified infection in white-tailed deer and several cattle herds adjacent to this index herd. In February 2008, Minnesota declared its 11th infected cattle herd, resulting in the downgrade of the entire State’s TB status to Modified Accredited (MA).
In an effort to minimize the impact of MA status to the State and producers, Minnesota initiated the …

Animal Health Matters, David H. Zeman

Animal Health MATTERS Newsletter

Head/Director's Message [Page] 1- Partnerships Matter Diagnostic News [Page] 1- Bovine Lead Poisoning: May and June are Peak Months for Diagnosis [Page] 3- Holiday Hours [Page] 3- Water Suitability for Livestock [Page] 4- Why can’t you just run it anyway? Research News [Page] 4- Research Spotlight: Dr. Chris Chase Extension News [Page] 5- State Veterinary Loan Repayment Programs –a Regional Review [Page] 6- Pieces and Parts Student News [Page] 7- SDSU Pre-Veterinary Students Admitted to Veterinary Colleges for Fall 2008 [Page] 7- 2008 – 2009 Vet Science Scholarship Award Recipients [Page] 7- Calendar of Events

Tetanus And Rabies Eradication In Pakistan; A Mission Not Impossible, Mohammad Wasay, Ismail A. Khatri, Naseem Salahuddin

Department of Medicine

No abstract provided.

Animal Health Matters, David H. Zeman

Animal Health MATTERS Newsletter

Head/Director's Message [Page] 1- University, College and Department Missions Diagnostic News [Page] 1- Hardware Disease Associated with Tires Used as Hay Feeding Stations: A New Source of Hardware for an Old Disease [Page] 2- Holiday Hours [Page] 2- Calf Scours Submissions at SDSU ADRDL [Page] 3- Calf Scours / Enteritis Submission Guidelines Research News [Page] 3- Research Spotlight: Alan J. Young, PhD – The Immunophysiology of Prion Diseases Extension News [Page] 4- New Vaccination Guidelines for Horses Released [Page] 5- Mineral Nutrition Short Course for Beef Cattle Veterinarians [Page] 5- Master of Public Health (MPH) Program for Practicing Veterinarians [Page] …

Brown Dog Tick: Vector For Rocky Mountain Spotted Fever, Craig Levy

Zoonotics and Wildlife Disease: Publications

The brown dog tick, Rhipicephalus sanguineus (Acari: Ixodidae), feeds primarily on dogs and until recently was not known to vector Rocky Mountain spotted fever (RMSF). In 2003–2004, fourteen cases of RMSF in humans occurred in eastern Arizona in the absence of known vectors, the Rocky Mountain wood tick, Dermacentor andersoni, and American dog tick, Dermacentor variabilis. However, health officials found brown dog ticks to be very abundant in areas associated with human cases, and the Centers for Disease Control and Prevention (CDC) implicated that the brown dog tick was responsible for transmitting RMSF. Brown dog ticks occur throughout the United …

Genomic Organization, Sequence Divergence, And Recombination Of Feline Immunodeficiency Virus From Lions In The Wild, Jill Pecon-Slattery, Carrie L. Mccracken, Jennifer L. Troyer, Sue Vandewoude, Melody E. Roelke, Kerry Sondgeroth, Christiaan Winterbach, Stephen J. O'Brien

Biology Faculty Articles

Background

Feline immunodeficiency virus (FIV) naturally infects multiple species of cat and is related to human immunodeficiency virus in humans. FIV infection causes AIDS-like disease and mortality in the domestic cat (Felis catus) and serves as a natural model for HIV infection in humans. In African lions (Panthera leo) and other exotic felid species, disease etiology introduced by FIV infection are less clear, but recent studies indicate that FIV causes moderate to severe CD4 depletion.

Results

In this study, comparative genomic methods are used to evaluate the full proviral genome of two geographically distinct FIV subtypes …

Genetic Characterization Of Feline Leukemia Virus From Florida Panthers, Meredith Brown, Mark W. Cunningham, Alfred L. Roca, Jennifer L. Troyer, Warren E. Johnson, Stephen J. O'Brien

Biology Faculty Articles

From 2002 through 2005, an outbreak of feline leukemia virus (FeLV) occurred in Florida panthers (Puma concolor coryi). Clinical signs included lymphadenopathy, anemia, septicemia, and weight loss; 5 panthers died. Not associated with FeLV outcome were the genetic heritage of the panthers (pure Florida vs. Texas/Florida crosses) and co-infection with feline immunodeficiency virus. Genetic analysis of panther FeLV, designated FeLV-Pco, determined that the outbreak likely came from 1 cross-species transmission from a domestic cat. The FeLV-Pco virus was closely related to the domestic cat exogenous FeLV-A subgroup in lacking recombinant segments derived from endogenous FeLV. FeLV-Pco sequences were …

South Dakota Animal Disease Research And Diagnostic Laboratory: Annual Report 2008, Animal Disease Research And Diagnostic Laboratory, South Dakota State University

South Dakota Animal Disease Research and Diagnostic Laboratory (ADRDL)

This document is the 2008 annual report of the South Dakota Veterinary and Biomedical Science Department Animal Disease Research and Diagnostic Laboratory.

Ecological Factors Associated With West Nile Virus Transmission, Northeastern United States, Heidi E. Brown, James E. Childs, Maria A. Diuk-Wasser, Durland Fish

Zoonotics and Wildlife Disease: Publications

Since 1999, West Nile virus (WNV) disease has affected the northeastern United States. To describe the spatial epidemiology and identify risk factors for disease incidence, we analyzed 8 years (1999–2006) of county-based human WNV disease surveillance data. Among the 56.6 million residents in 8 northeastern states sharing primary enzootic vectors, we found 977 cases. We controlled for population density and potential bias from surveillance and spatial proximity. Analyses demonstrated significant spatial spreading from 1999 through 2004 (p2 = 0.16). A significant trend was apparent among increasingly urban counties; county quartiles with the least (0.75 cases/100,000 residents) than counties with the …

Myenteric Neurons Of The Ileum That Express Somatostatin Are A Target Of Prion Neuroinvasion In An Alimentary Model Of Sheep Scrapie, David A. Schneider, Huijun Yan, Lindsay M. Fry, Janet Alverson, Stephen N. White, Katherine I. O'Rourke

Zoonotics and Wildlife Disease: Publications

Neuroinvasion of the enteric nervous system by prions is an important step in dissemination to the brain, yet very little is known about the basic process of enteric neuroinvasion. Using an alimentary model of neonatal disease transmission, neuroinvasion by scrapie prions in the ileum of lambs was detected by immunohistochemical staining for the disease-associated form of the prion protein, PrP^Sc. Odds ratios (OR) were determined for the frequency of PrP^Sc staining within enteric somata categorized by plexus location (myenteric, submucosal) and neurochemical staining (PGP 9.5, neural nitric oxide synthase, somatostatin, substance P, and vasoactive intestinal polypeptide). PrP …

Prion Gene (Prnp) Haplotype Variation In United States Goat Breeds, Stephen N. White, Lynn Herrmann-Hoesing, Katherine I. O'Rourke, Daniel Waldron, Joan Rowe, Janet Alverson

Zoonotics and Wildlife Disease: Publications

Scrapie eradication efforts cost 18 million dollars annually in the United States and rely heavily upon PRNP genotyping of sheep. Genetic resistance might reduce goat scrapie and limit the risk of goats serving as a scrapie reservoir, so PRNP coding sequences were examined from 446 goats of 10 breeds, 8 of which had not been previously examined at PRNP. The 10 observed alleles were all related to one of two central haplotypes by a single amino acid substitution. At least five of these alleles (M142, R143, S146, H154, and K222) have been associated with increased incubation time or decreased …

A Species Barrier Limits Transmission Of Chronic Wasting Disease To Mink (Mustela Vison), Robert D. Harrington, Timothy V. Baszler, Katherine I. O'Rourke, David A. Schneider, Terry R. Spraker, H. Denny Liggitt, Donald P. Knowles

Zoonotics and Wildlife Disease: Publications

Transmissible mink encephalopathy (TME) occurs as sporadic outbreaks associated with ingestion of feed presumably contaminated with some type of prion disease. Mink lack a species barrier to primary oral challenge with bovine spongiform encephalopathy, whereas they have a barrier to such challenge with scrapie. We investigated whether mink have a species barrier to chronic wasting disease (CWD) by performing primary intracerebral (IC) and primary oral challenge with CWD-positive elk brain. Primary IC challenge resulted in clinical disease in two of eight mink at 31–33 months incubation. Affected mink had spongiform vacuolation and astrocytosis within the central nervous system and immunoreactivity …

Scrapie Resistance In Arq Sheep, W. W. Laegreid, M. L. Clawson, M. P. Heaton, B. T. Green, Katherine I. O'Rourke, D. P. Knowles

Zoonotics and Wildlife Disease: Publications

Variation in the ovine prion protein amino acid sequence influences scrapie progression, with sheep homozygous for A¹³⁶R¹⁵⁴Q¹⁷¹ considered susceptible. This study examined the association of survival time of scrapie-exposed ARQ sheep with variation elsewhere in the ovine prion gene. Four single nucleotide polymorphism alleles were associated with prolonged survival. One nonsynonymous allele (T112) was associated with an additional 687 days of survival for scrapie-exposed sheep compared to M112 sheep (odds ratio, 42.5; P = 0.00014). The only two sheep homozygous for T112 (TARQ) did not develop scrapie, suggesting that the allelic effect may be additive. …

A Collaborative Canadian–United Kingdom Evaluation Of An Immunohistochemistry Protocol To Diagnose Bovine Spongiform Encephalopathy, Lisa Manning, Katherine I. O'Rourke, Donald P. Knowles, Sarah A. Marsh, Yvonne I. Spencer, Estella Moffat, Gerald A. H. Wells, Stefanie Czub

Zoonotics and Wildlife Disease: Publications

Collaboration was established in 2001 to evaluate a commercially available immunohistochemistry assay kit for the detection of bovine spongiform encephalopathy (BSE) disease–associated prion protein in formic acid–treated formalin-fixed samples of bovine brain. The kit protocol was evaluated at the National Centre for Foreign Animal Diseases (Winnipeg, Canada) and the Veterinary Laboratories Agency (Weybridge, U.K.). The U.K. laboratory provided paraffin-embedded blocks of brainstem (medulla oblongata at the level of the obex) from 100 positive cases defined by clinical signs and histopathology, and 100 clinically suspect but BSE-negative samples defined by histopathology and immunohistochemistry with anti-PrP monoclonal antibody R145. The Canadian laboratory …

Experimental Transmission Of Chronic Wasting Disease (Cwd) Of Elk (Cervus Elaphus Nelsoni), White-Tailed Deer (Odocoileus Virginianus), And Mule Deer (Odocoileus Hemionus Hemionus) To White-Tailed Deer By Intracerebral Route, A. N. Hamir, J. A. Richt, J. M. Miller, R. A. Kunkle, S. M. Hall, E. M. Nicholson, Katherine I. O'Rourke, J. J. Greenlee, E. S. Williams

Zoonotics and Wildlife Disease: Publications

To compare clinical and pathologic findings of chronic wasting disease (CWD) in a natural host, 3 groups (n = 5) of white-tailed deer (WTD) fawns were intracerebrally inoculated with a CWD prion of WTD, mule deer, or elk origin. Three other uninoculated fawns served as controls. Approximately 10 months postinoculation (MPI), 1 deer from each of the 3 inoculated groups was necropsied and their tissues were examined for lesions of spongiform encephalopathy (SE) and for the presence of abnormal prion protein (PrP^d) by immunohistochemistry (IHC) and Western blot (WB). The remaining deer were allowed to live until …

Chronic Wasting Disease In A Wisconsin White-Tailed Deer Farm, Delwyn P. Keane, Daniel J. Barr, Phillip N. Bochsler, S. Mark Hall, Thomas Gidlewski, Katherine I. O'Rourke, Terry R. Spraker, Michael D. Samuel

Zoonotics and Wildlife Disease: Publications

In September 2002, chronic wasting disease (CWD), a prion disorder of captive and wild cervids, was diagnosed in a white-tailed deer (Odocoileus virginianus) from a captive farm in Wisconsin. The facility was subsequently quarantined, and in January 2006 the remaining 76 deer were depopulated. Sixty animals (79%) were found to be positive by immunohistochemical staining for the abnormal prion protein (PrP^CWD) in at least one tissue; the prevalence of positive staining was high even in young deer. Although none of the deer displayed clinical signs suggestive of CWD at depopulation, 49 deer had considerable accumulation of …

Animal-Side Serologic Assay For Rapid Detection Of Mycobacterium Bovis Infection In Multiple Species Of Free-Ranging Wildlife, K.P. Lyashchenko, R. Greenwald, J. Esfandiari, M.A. Chambers, J. Vicente, C. Gortazar, N. Santos, M. Correia-Neves, B.M. Buddle, R. Jackson, D.J. O’Brien, S. Schmitt, M. V. Palmer, R.J. Delahay, W.R. Waters

Michigan Bovine Tuberculosis Bibliography and Database

Numerous species of mammals are susceptible to Mycobacterium bovis, the causative agent of bovine tuberculosis (TB). Several wildlife hosts have emerged as reservoirs of M. bovis infection for domestic livestock in different countries. In the present study, blood samples were collected from Eurasian badgers (n = 1532), white-tailed deer (n = 463), brushtail possums (n = 129), and wild boar (n = 177) for evaluation of antibody responses to M. bovis infection by a lateral-flow rapid test (RT) and multiantigen print immunoassay (MAPIA). Magnitude of the antibody responses and antigen recognition patterns varied among the animals as determined by …

Immunomodulatory And Protective Effects Of Sugar Cane Juice In Chickens Against Eimeria Infection, Masood Akhtar, M. Abdul Hafeez, Faqir Muhammad, Ahsan Ul Haq, M. Irfan Anwar

Turkish Journal of Veterinary & Animal Sciences

Present paper reports the effects of sugar cane juice (SCJ) on immune responses and its protection against Eimeria (mixed species) infections in broiler chickens. Experiment 1 was conducted to test the dose efficacy of SCJ and its effects on chickens against coccidiosis. Maximum weight gain per day was recorded in chickens given SCJ @ 400 mg/kg body weight. Significantly (P < 0.01) low mortality and increased body weight gain per day were recorded in chickens administered SCJ orally and challenged with mixed species of genus Eimeria. Furthermore, mild hemorrhages, lower lesion scores (+1), and significantly lower number of oocysts shed in faeces were recorded in immunized chickens compared to control. Experiment 2 was carried out to evaluate the immunomodulatory effects of SCJ on cellular and humoral responses. Highest antibody titres (1:1024-1:16; GMT 367.28) were recorded in chickens administered SCJ @ 400 mg/kg body weight in comparison with control (1:16-1:2; GMT 2.82). To demonstrate the cell mediated immunity (CMI), amplitude of toe-web swelling 72 h post avian tuberculin injection was recorded in the experimental and control groups. Maximum swelling (8.13 ± 0.21 mm) was recorded in the experimental group as compared to control (1.04 ± 0.10); indicating higher cell mediated immune response. From these results it was concluded that SCJ elicit a significantly higher cellular and humoral responses compared to control, which may provide protection against Eimeria infections (mixed species) in chickens.

Michigan Bovine Tuberculosis Eradication Project: 2008 Activities Report

Michigan Bovine Tuberculosis Bibliography and Database

Bovine Tuberculosis (TB) is an infectious disease that is close to being eradicated in the United States, but still poses a significant risk to domestic livestock, wildlife, companion animals, and humans throughout the world. The Michigan Bovine TB Eradication Project involves a multiagency team of experts from the Michigan Departments of Agriculture, Natural Resources and Community Health, Michigan State University, and the US Department of Agriculture.

Managing Bovine Tuberculosis In White-Tailed Deer In Northwestern Minnesota: A 2008 Progress Report, Michelle Carstensen, Erika Butler, Michael Doncarlos, Lou Cornicelli

Michigan Bovine Tuberculosis Bibliography and Database

Bovine tuberculosis (TB), first discovered in 2005, has now been found in 12 cattle operations in northwestern Minnesota. To date, all of the infected cattle herds have been depopulated and the Board of Animal Health (BAH) has continued to test cattle herds in the area. The strain has been identified as one that is consistent with Bovine TB found in cattle in the southwestern United States and Mexico. In response to the disease being detected in cattle, the Minnesota Department of Natural Resources (MNDNR) began surveillance efforts in free-ranging white-tailed deer (Odocoileus virginianus) within a 15-mile radius of …

Blood Culture And Stimulation Conditions For The Diagnosis Of Tuberculosis In Cervids By The Cervigam Assay, W. R. Waters, M. V. Palmer, T. C. Thacker, K. Orloski, P. Nol, N. P. Harrington, S. C. Olsen, B. J. Nonnecke

Michigan Bovine Tuberculosis Bibliography and Database

Mitogen- and antigen-induced interferon-γ (IFN-γ) responses of peripheral blood leucocytes from cervids were evaluated by a commercial whole-blood assay. The assay was applied to Mycobacterium bovis-infected white-tailed deer and reindeer, M bovis BCG-vaccinated white-tailed deer and elk, and unvaccinated, uninfected white-tailed deer, fallow deer, elk and reindeer. The responses of the M bovis-infected white-tailed deer to pokeweed mitogen (PWM) varied with time and between individuals. The responses of the M bovis-infected reindeer to PWM and M bovis purified protein derivative (PPD) were positively associated. Samples from tuberculosis-free captive herds in various parts of the USA were also …

Sentinel-Based Surveillance Of Coyotes To Detect Bovine Tuberculosis, Michigan, Kurt C. Vercauteren, Todd C. Atwood, Thomas J. Deliberto, Holly J. Smith, Justin S. Stevenson, Bruce V. Thomsen, Thomas Gidlewski, Janet Payeur

Michigan Bovine Tuberculosis Bibliography and Database

Bovine tuberculosis (TB) is endemic in white-tailed deer (Odocoileus virginianus) in the northeastern portion of Michigan’s Lower Peninsula. Bovine TB in deer and cattle has created immense fi nancial consequences for the livestock industry and hunting public. Surveillance identified coyotes (Canis latrans) as potential bio-accumulators of Mycobacterium bovis, a finding that generated interest in their potential to serve as sentinels for monitoring disease risk. We sampled 175 coyotes in the bovine TB–endemic area. Fifty-eight tested positive, and infection prevalence by county ranged from 19% to 52% (statistical mean 33%, SE 0.07). By contrast, prevalence in …

Randomized Controlled Trial Evaluating Adeno-Momp And Momp Dna Vaccines Against Chlamydophila Psittaci Challenge In Cockatiels (Nymphicus Hollandicus), David Sanchez-Migallon Guzman

LSU Master's Theses

Chlamydophila psittaci causes severe disease in birds and humans, and important economical losses in the avian companion and poultry industry. Vaccines are the most cost-effective measure to control and help prevent infectious diseases, but to date there is no commercial vaccine available. A randomized clinical trial was conducted to assess the efficacy of two recombinant DNA vaccines against C. psittaci in Cockatiels (Nymphicus hollandicus). The first recombinant DNA vaccine has a gene encoding MOMP and the immunostimulant chitosan (MOMP DNA vaccine). The second recombinant DNA vaccine, contained the gene encoding MOMP that was vectored by a replication defective human adenovirus …

The Influence Of Veterinary Schools On The Veterinary Labor Market, Kyle Bosh

MPA/MPP/MPFM Capstone Projects

Problem Statement:

Does the presence of a veterinary school in a state influence the supply of veterinarians practicing in that state? Citizens and animals in states without a veterinary school are at a disadvantage if the presence of a veterinary school significantly improves public health and access to medical services in those states that have a veterinary school.

Research Strategy:

The unit of analysis in this study is 50 states and the District of Columbia. The study is designed as a cross-sectional analysis of 2006 pet, 2002 livestock, 2006 human, labor, and economic data. The study uses simultaneous equations to …

Small-Ruminant Lentivirus Enhances PrpSc Accumulation In Cultured Sheep Microglial Cells, James B. Stanton, Donald P. Knowles, Katherine I. O'Rourke, Lynn M. Herrmann-Hoesing, Bruce A. Mathison, Timothy V. Baszler

Zoonotics and Wildlife Disease: Publications

Sheep scrapie is the prototypical transmissible spongiform encephalopathy (prion disease), which has a fundamental pathogenesis involving conversion of normal cellular prion protein (PrP^C [C superscript stands for cellular]) to disease-associated prion protein (PrP^Sc [Sc superscript stands for sheep scrapie]). Sheep microglial cell cultures, derived from a prnp 136VV/171QQ near-term fetal brain, were developed to study sheep scrapie in the natural host and to investigate potential cofactors in the prion conversion process. Two culture systems, a primary cell culture and a cell line transformed with the large T antigen of simian virus 40, were developed, and both were identified …

Bovine Herpesvirus Type 1 Induces Cell Death By A Cell Type Dependent Fashion, Vicki Geiser, Suzanne Rose, Clinton J. Jones

School of Veterinary and Biomedical Sciences: Faculty Publications

Bovine herpesvirus 1 (BHV-1), a member of the alpha-herpesvirinae subfamily, causes significant losses to the cattle industry. BHV-1 establishes latency in trigeminal ganglionic sensory neurons, but periodically reactivates from latency. Previous studies suggested that infection with BHV-1 induced novel morphological changes in rabbit skin cells (RS) versus bovine kidney cells (MDBK). Consequently, we hypothesized that viral infection led to a novel form of cell death in RS cells compared to MDBK cells. To test this hypothesis, we examined the levels of apoptosis in these cell types following infection with BHV-1. Infection of RS, but not MDBK, cells leads to high …

Advancing Epidemiological Science Through Computational Modeling: A Review With Novel Examples, Scott M. Duke-Sylvester, Eli N. Perencevich, Jon P. Furuno, Leslie A. Real, Holly Gaff

Biological Sciences Faculty Publications

Computational models have been successfully applied to a wide variety of research areas including infectious disease epidemiology. Especially for questions that are difficult to examine in other ways, computational models have been used to extend the range of epidemiological issues that can be addressed, advance theoretical understanding of disease processes and help identify specific intervention strategies. We explore each of these contributions to epidemiology research through discussion and examples. We also describe in detail models for raccoon rabies and methicillin-resis-tant Staphylococcus aureus, drawn from our own research, to further illustrate the role of computation in epidemiological modeling.

Seroprevalence Of Brucellosis In Human, Cattle, And Buffalo Populations In Pakistan, Iftikhar Hussain, Muhammad Imran Arshad, Muhammad Shahid Mahmood, Masood Akhtar

Turkish Journal of Veterinary & Animal Sciences

A total of 1500 serum samples were collected from cattle, buffaloes, and humans. The Rose Bengal plate test (RBPT) and enzyme-linked immunosorbent assay (ELISA) detected Brucella antibodies in 56 (10.18%) and 44 (8%) of the cattle, respectively. In samples collected from buffaloes 9.38% and 6.92% were positive, whereas 14% and 11% of the samples from humans were found to be positive by RBPT and ELISA, respectively. Among village workers a higher prevalence of brucellosis was recorded in females than in males. Abattoir-associated personnel also had a higher incidence of brucellosis. Results of the present study revealed that RBPT and ELISA …

Disseminated Streptococcus Equi Subsp. Zooepidemicus Infection In A Foal And Associated Mastitis In A Mare, A. Levent Kocabiyik, Esra Büyükcangaz, Ahmet Akkoç, Cüneyt Özakin, İ. Taci̇ Cangül

Turkish Journal of Veterinary & Animal Sciences

A systemic infection with Streptococcus equi subsp. zooepidemicus is described in a 22-day-old female foal for the first time in Turkey. Clinically the foal was in poor condition and had severe pneumonia. Painful swellings of the carpal and tarsal joints were evident. Examination of the dam revealed clinical mastitis. Postmortem histopathological and microbiological examinations of samples from the foal revealed a disseminated infection with S. equi subsp. zooepidemicus. The causative agent was also recovered in pure culture from a milk sample of the mare.

Reduced Intestinal Colonization Of Adult Beef Cattle By Escherichia Coli O157:H7 Tir Deletion And Nalidixic-Acid-Resistant Mutants Lacking Flagellar Expression, Gustavo Bretschneider, Emil M. Berberov, Rodney A. Moxley

School of Veterinary and Biomedical Sciences: Faculty Publications

The importance of the Escherichia coli O157:H7 translocated intimin receptor (Tir) protein in intestinal colonization and the effect of infection with Tir⁺ strains on protection against subsequent challenge was studied in adult beef cattle. Cattle were orally inoculated (C1) with a Shiga toxin-2⁺+ E. coli O157:H7 strain that was Tir⁺ or Tir^-, and 42 days later were re-challenged (C2) with the nalidixic acid (Nal) ^R parent strain to test whether prior infection had any effect on fecal shedding. During the first 14 days post-C1, the Nal^S wildtype (WT) strain was shed at significantly …