Bovine digital dermatitis: natural lesion development and experimental induction

Bovine Digital Dermatitis (DD) is a leading cause of lameness in dairy cattle in the US with more than 70% of herds affected. Despite 40 years of research, the definitive etiologic agent(s) associated with the disease process is unknown. While clinical lesions have been well described, little is known about the macroscopic, microscopic, and bacterial changes associated with the early stages of lesion development from normal skin to clinical lesions. The goal of this dissertation was to describe the temporal changes associated with lesion development in Holstein dairy cattle, particularly early stage lesions, and develop a model for lesion induction. By following a cohort of Holstein dairy cows for a three year period, several important epidemiologic findings were recognized. In the absence of control measures, DD lesions developed at a rate of 4 lesions per 100 cow feet-months, with the average time for a lesion to develop being 133 days. From the recognition of the macroscopic changes that preceded clinical DD lesions, a novel scoring system was developed. While 20% of the feet observations had clinical DD lesions, an additional 55% of observations had lesions that were indicative of early DD lesion development. Biopsies from these different stages of lesion development were submitted for metagenomic analysis using next generation sequencing. The bacterial microbiota of these biopsies was found to progress through a systematic series of changes that correlate with the macroscopic lesion scoring system with the microbiota of each stage being statistically different from other stages. As one of the major goals for these studies was to gain a better understanding of the etiology of disease, an experimental model was needed to test candidate pathogens. Four preliminary studies were conducted to optimize conditions and methodologies for induction of DD lesions that led to a final consensus protocol that was able to induce DD lesions in 95% of Holstein calves within 28 days. The results of these studies support the hypothesis that DD is a polybacterial disease process that undergoes systematic macroscopic, microscopic, and bacterial changes as lesions develop

Clinical presentations and antimicrobial susceptibilities of Corynebacterium cystitidis associated with renal disease in four beef cattle

Background Renal disease caused by Corynebacterium cystitidis in beef cattle may be misclassified as Corynebacterium renale, and limited information about C. cystitidis infections in beef cattle currently is available. Objective To describe clinical presentation, diagnosis, minimum inhibitory concentrations (MICs), and outcome of renal disease caused by C. cystitidis in beef cattle. Methods Retrospective case series. Animals Four client-owned beef cattle. Results All affected cattle had anorexia as a primary complaint. Of the 3 that had ante-mortem diagnostic tests performed, all had pyelonephritis based on azotemia in combination with urinalysis and ultrasonographic findings. Cultures yielded C. cystitidis which was identified by biochemical testing, 16S RNA sequencing, and mass spectrometry. All affected cattle deteriorated despite aggressive treatment, indicating that C. cystitidis infections in beef cattle may carry a poor prognosis. Bacterial isolates collected from the 4 cattle showed similarities in MICs for ampicillin, florfenicol, gentamicin, neomycin, sulfadimethoxine, trimethoprim sulfonamide, and tylosin. Conclusions and clinical importance Corynebacterium cystitidis should be considered in the differential diagnosis of cattle with renal disease. Definitive diagnosis of C. cystitidis as compared to C. renale may be challenging

Changes in the prevalence of Salmonella serovars associated swine production and correlations of avian, bovine and swine‐associated serovars with human‐associated serovars in the United States (1997–2015)

As Salmonella enterica is an important pathogen of food animals, surveillance programmes for S. enterica serovars have existed for many years in the United States. Surveillance programmes serve many purposes, one of which is to evaluate alterations in the prevalence of serovars that may signal changes in the ecology of the target organism. The primary aim of this study was to evaluate changes in the proportion of S. enterica serovars isolated from swine over a near 20‐year observation period (1997–2015) using four longitudinal data sets from different food animal species. The secondary aim was to evaluate correlations between changes in S. enterica serovars frequently recovered from food animals and changes in S. enterica serovars associated with disease in humans. We found decreasing proportions of S. enterica serovar Typhimurium, serovar Derby and serovar Heidelberg and increasing proportions of S. enterica serovar 4,[5],12:i:‐, serovar Infantis and serovar Johannesburg in swine over time. We also found positive correlations for the yearly changes in S. enterica serovar 4,[5],12:i:‐, serovar Anatum and serovar Johannesburg between swine and human data; in S. enterica Worthington between avian and human data; and in S. enterica serovar 4,[5],12:i:‐ between bovine and human data. We found negative correlations for the yearly changes in S. enterica serovar 4,[5],12:i:‐ and serovar Johannesburg between avian and human data.This article is published as Yuan, C., A. Krull, C. Wang, M. Erdman, P. J. Fedorka‐Cray, C. M. Logue, and A. M. O'Connor. "Changes in the prevalence of Salmonella serovars associated swine production and correlations of avian, bovine and swine‐associated serovars with human‐associated serovars in the United States (1997–2015)." Zoonoses and Public Health (2018). DOI: 10.1111/zph.12473. Posted with permission.</p

Macroscopic Lesion Scoring System.

<p>Macroscopic Lesion Scoring System.</p

Lesion Grades for each Macroscopic Lesion Score.

<p>Histopathology score summary from each of the macroscopic scores. As biopsies were only taken from feet with visible lesions, the majority of the lesions scores were 6 or greater. Several lesion scores of 4 and 5 were included in the <6 category. The grade 1 category encompassed all biopsies identified as normal bovine skin. Grade 2 lesions were described as hyperkeratosis, acanthosis with surface hemorrhage and erythrocytic crusts. Grade 3 lesions were described as segmental localized necrotizing to necrosuppurative epidermitis with individual cell necrosis, ballooning degeneration of epithelial cells, necrotizing vasculitis, intralesional bacteria consisting of delicate spirochetes, bacilli, and coccobacilli.</p

The Number of Lame Feet for Each of Protocol.

<p>The Number of Lame Feet for Each of Protocol.</p

A summary of each protocol evaluated during the five experiments.

<p>A summary of each protocol evaluated during the five experiments.</p

Association between antimicrobial drug class for treatment and retreatment of bovine respiratory disease (BRD) and frequency of resistant BRD pathogen isolation from veterinary diagnostic laboratory samples.

Although 90% of BRD relapses are reported to receive retreatment with a different class of antimicrobial, studies examining the impact of antimicrobial selection (i.e. bactericidal or bacteriostatic) on retreatment outcomes and the emergence of antimicrobial resistance (AMR) are deficient in the published literature. This survey was conducted to determine the association between antimicrobial class selection for treatment and retreatment of BRD relapses on antimicrobial susceptibility of Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni. Pathogens were isolated from samples submitted to the Iowa State University Veterinary Diagnostic Laboratory from January 2013 to December 2015. A total of 781 isolates with corresponding animal case histories, including treatment protocols, were included in the analysis. Original susceptibility testing of these isolates for ceftiofur, danofloxacin, enrofloxacin, florfenicol, oxytetracycline, spectinomycin, tilmicosin, and tulathromycin was performed using Clinical and Laboratory Standards Institute guidelines. Data were analyzed using a Bayesian approach to evaluate whether retreatment with antimicrobials of different mechanistic classes (bactericidal or bacteriostatic) increased the probability of resistant BRD pathogen isolation in calves. The posterior distribution we calculated suggests that an increased number of treatments is associated with a greater probability of isolates resistant to at least one antimicrobial. Furthermore, the frequency of resistant BRD bacterial isolates was greater with retreatment using antimicrobials of different mechanistic classes than retreatment with the same class. Specifically, treatment protocols using a bacteriostatic drug first followed by retreatment with a bactericidal drug were associated with a higher frequency of resistant BRD pathogen isolation. In particular, first treatment with tulathromycin (bacteriostatic) followed by ceftiofur (bactericidal) was associated with the highest probability of resistant M. haemolytica among all antimicrobial combinations. These observations suggest that consideration should be given to antimicrobial pharmacodynamics when selecting drugs for retreatment of BRD. However, prospective studies are needed to determine the clinical relevance to antimicrobial stewardship programs in livestock production systems

Clinical presentations and antimicrobial susceptibilities of Corynebacterium cystitidis

Background Renal disease caused by Corynebacterium cystitidis in beef cattle may be misclassified as Corynebacterium renale, and limited information about C. cystitidis infections in beef cattle currently is available. Objective To describe clinical presentation, diagnosis, minimum inhibitory concentrations (MICs), and outcome of renal disease caused by C. cystitidis in beef cattle. Methods Retrospective case series. Animals Four client-owned beef cattle. Results All affected cattle had anorexia as a primary complaint. Of the 3 that had ante-mortem diagnostic tests performed, all had pyelonephritis based on azotemia in combination with urinalysis and ultrasonographic findings. Cultures yielded C. cystitidis which was identified by biochemical testing, 16S RNA sequencing, and mass spectrometry. All affected cattle deteriorated despite aggressive treatment, indicating that C. cystitidis infections in beef cattle may carry a poor prognosis. Bacterial isolates collected from the 4 cattle showed similarities in MICs for ampicillin, florfenicol, gentamicin, neomycin, sulfadimethoxine, trimethoprim sulfonamide, and tylosin. Conclusions and clinical importance Corynebacterium cystitidis should be considered in the differential diagnosis of cattle with renal disease. Definitive diagnosis of C. cystitidis as compared to C. renale may be challenging