A randomized trial to evaluate the effect of a trace mineral premix on the incidence of active digital dermatitis lesions in cattle.

A balanced, parallel-group, single-blinded randomized efficacy study divided into 2 periods was conducted to evaluate the effect of a premix containing higher than typically recommended levels of organic trace minerals and iodine (HOTMI) in reducing the incidence of active digital dermatitis (DD) lesions acquired naturally and induced by an experimental infection challenge model. For the natural exposure phase of the study, 120 healthy Holstein steers 5 to 7 mo of age without signs of hoof disease were randomized into 2 groups of 60 animals. The control group was fed a standard trace mineral supplement and the treatment group was fed the HOTMI premix, both for a period of 60 d. On d 60, 15 steers free of macroscopic DD lesions were randomly selected from each group for the challenge phase and transported to an experimental facility, where they were acclimated and then challenged within a DD infection model. The same diet group allocation was maintained during the 60 d of the challenge phase. The primary outcome measured was the development of an active DD lesion greater than 20mm in diameter across its largest dimension. No lesions were identified during the natural exposure phase. During the challenge phase, 55% (11/20) and 30% (6/20) of feet were diagnosed with an active DD lesion in the control and treatment groups, respectively. Diagnosis of DD was confirmed by histopathologic demonstration of invasive Treponema spp. within eroded and hyperplastic epidermis and ulcerated papillary dermis. All DD confirmed lesions had dark-field microscopic features compatible with DD and were positive for Treponema spp. by PCR. As a secondary outcome, the average DD lesion size observed in all feet was also evaluated. Overall mean (standard deviation) lesion size was 17.1 (2.36) mm and 11.1 (3.33) mm for the control and treatment groups, respectively, with this difference being driven by acute DD lesions >20mm. A trend existed for the HOTMI premix to reduce the total DD infection rate and the average size of the experimentally induced lesions. Further research is needed to validate the effect of this intervention strategy in the field and to generate prevention and control measures aimed at optimizing claw health based on nutritional programs.

An experimental infection model to induce digital dermatitis infection in cattle.

Bovine digital dermatitis (DD), also known as papillomatous digital dermatitis (foot warts), has been recognized as a major cause of lameness in cattle, with important economic and welfare consequences. The evaluation of therapeutic and preventive interventions aiming to control DD infections in dairy cattle is often challenged by the complex multifactorial etiology of the disease. An experimental infection model to induce acute DD lesions in a controlled environment is proposed. The goal was to provide a standard way of reproducing DD infections independent of external factors that could confound the natural course of the disease, such as management practices or infection pressure, resulting in transmission of DD between animals. A group of 4 yearling Holstein heifers free of any clinical evidence of hoof disease was recruited from a commercial dairy farm and housed in an experimental facility in 1 pen with slatted flooring. The hind feet were wrapped to mimic conditions of prolonged moisture (maceration) and reduced access to air (closure) and inoculated at the heel and dewclaw areas with a homogenate of a naturally occurring DD lesion skin biopsy or a culture broth of Treponema spp. After a period of 12 to 25 d, 4 of 6 and 1 of 4 dewclaw areas inoculated with biopsied DD lesion or a Treponema spp. culture, respectively, had gross lesions compatible with DD. Histopathology confirmed the gross diagnosis in the sites inoculated with tissue homogenate. In the site inoculated with Treponema spp. culture broth, histopathology revealed an incipient DD lesion. Treponema spp. were detected by PCR in both naturally occurring DD homogenate and Treponema spp. culture broth inoculation sites. An experimental infection model to induce acute DD in cattle was developed, which may be used to evaluate interventions to control DD and study the pathogenesis of this infectious hoof disease in a controlled manner.

Zygomycotic lymphadenitis in slaughtered feedlot cattle.

During the 12 months of 2006, zygomycotic lymphadenitis was diagnosed in 194 of 198 feedlot steers (0.04% of cattle slaughtered during that period) in a California slaughterhouse as part of bovine tuberculosis surveillance. Mesenteric lymph nodes were involved in 190 cases. Affected lymph nodes were enlarged (2 to 42 cm in greatest dimension), firm, and mottled gray-white to yellow with multiple granular or caseocalcareous foci. Histologically, nodal architecture was effaced by necrosis, granulomatous inflammation, and fibrosis. In approximately 20% of the cases, granulomas were mainly restricted to subcapsular sinuses and afferent lymphatic vessels, causing granulomatous lymphangitis. Nonseptate, irregularly branching hyphae with nonparallel walls and bulbous enlargements were common in necrotic areas and within the cytoplasm of multinucleated giant cells. Fungal cultures were performed on 124 affected lymph nodes using 7 media, but no zygomycetes were cultured. Fungal DNA was amplified from 20 lymph nodes. Amplicons from 16 nodes had nearly 100% homology with sequences for Rhizomucor pusillus; 4 amplicons had (> 98%) homology with Absidia corymbifera sequences. Zygomycosis should be considered in the differential diagnosis for granulomatous lymphadenitis in feedlot steers.

Genetic diversity of bovine ulcerative mammary dermatitis-associated Treponema.

The etiology of bovine ulcerative mammary dermatitis (UMD) is poorly characterized. The goal of this study was to genetically analyze spirochetes present in UMD lesions. DNA prepared from UMD lesion biopsies and from spirochetes cultured from the corresponding lesion biopsies was PCR amplified using primers for the 16S rDNA-tRNA(ile) intergenic spacer region (ISR) of Treponema 16S-23S rDNA. Analysis of cloned ISR amplicons from three cultivable UMD-associated spirochetes indicated that two isolates cluster closely with cultivable papillomatous digital dermatitis (PDD)-associated and human-associated Treponema phylotypes, while the remaining isolate is unique. Analysis of ISR amplicons from UMD lesion biopsies identified additional not-yet-cultivable Treponema phylotypes. Our results revealed the presence of a genetically diverse Treponema population in an UMD lesion.

Farm- and host-level risk factors for papillomatous digital dermatitis in Chilean dairy cattle.

A cross-sectional study was conducted in southern Chile between January and March, 1996, to identify risk factors for papillomatous digital dermatitis (PDD) in lactating dairy and dual-purpose cows. A total of 3,265 cows from 22 farms were examined in the milking parlor for PDD lesions. Additional information was collected from dairies' computerized records and by direct interview of managers. Data were analyzed using logistic and logistic-binomial regression (with dairy as a random-effect term). German Red-Pied (dual-purpose) cows were significantly (P < 0.05) less likely (odds ratio (OR) = 0.3) to have PDD lesions than German Black-Pied and Holstein crossbreds. First-parity cows had the highest odds of PDD, and odds diminished, in a dose-effect manner, as parity increased. Odds of PDD increased with increasing days in lactation. Cows that calved during winter were more likely to have PDD (OR = 1.4) than those calving at any other season. Cows on farms that bought heifers in the past 10 years had a 3-fold increase in the odds of PDD compared to those on farms that never bought heifers. Loose-housed cows had a higher risk of PDD (OR = 7), followed by cows in free stalls or in open corrals (OR = 2.8 and 1.3, respectively), compared to cows on pasture all year. Cows on dairies that used a footbath during 1996 were less likely (OR = 0.3) to have PDD than those in dairies not using one. Parlor type was associated with PDD, but this was likely an effect of parlor design on ease of inspection of cows' feet. A policy of trimming all cows' vs. only lame cows' feet and a policy about buying adult cows did not have significant effects on PDD risk.

Papillomatous digital dermatitis in Chilean dairies and evaluation of a screening method.

Outbreaks of papillomatous digital dermatitis (PDD) have been reported from many countries, but there is little information on prevalence and geographic distribution of the disease. Our objectives were to describe prevalence of PDD on dairies belonging to the two main dairy-producer associations in Chile, and to evaluate a milking-parlor screening method for detection of PDD in dairy cows. First, a self-administered questionnaire was sent to all 214 association dairy managers. Seventy percent of the 119 respondents had observed PDD on their dairies. About 83% of the 63 responding managers had first seen PDD during the previous 10 years. Subsequently, a random sample of 43 dairies stratified by association was selected from the total 214 for PDD screening. During milking, we inspected cows' feet for PDD lesions; 91% of dairies had cows affected by PDD; median PDD prevalence for milking cows in dairies was 6.1%. Finally, in one dairy, PDD screening at the parlor was compared to PDD diagnosis by inspecting restrained cows in a chute. The screening method had a sensitivity of 0.72, and a specificity of 0.99. This study demonstrated that PDD was widespread on study dairies in Chile. The screening test presented can be used as a cost efficient method to estimate prevalence of PDD either on individual dairies or in large-scale surveys.

Spirochetes isolated from dairy cattle with papillomatous digital dermatitis and interdigital dermatitis.

Two groups of spirochetes were isolated from papillomatous digital dermatitis (PDD) lesions in dairy cattle. The two groups could be readily differentiated on the basis of morphologic and immunologic characteristics and enzymatic activity. A spirochete isolated from an interdigital dermatitis (IDD) lesion appeared morphologically and antigenically similar to spirochetes in one of the PDD groups and exhibited an identical enzyme activity pattern. The two groups of PDD spirochetes had characteristics most consistent with the genus Treponema. The PDD and IDD isolates differed morphologically from previously described bovine Treponema spp. Although spirochetes have been observed to be one of the predominant bacterial morphotypes in PDD and IDD and are found invading the stratum spinosum and dermal papillae in PDD lesions, the significance of these spirochetes in the etiopathogenesis of PDD and IDD is presently unknown.

Glycemic modulation of tumor tolerance in a mouse model of breast cancer.

Marked sensitivity of tumor tolerance to blood glucose level is demonstrated in a mouse model of human breast cancer. A theory is cited that explains the high association of hyperglycemia with malignancy, especially breast cancer, via glycemic modulation of cellular immunity. Three groups of BALB/C mice were injected with an aggressive mammary tumor and placed on three dietary regimens designed to produce three different glycemic levels. Mortalities 70 days after injection were 16 of 24 hyperglycemic mice, 8 of 24 normoglycemic, and 1 of 20 hypoglycemic (chi-square p less than .005). Taken together with other experiments and human data discussed briefly, this result suggests that glycemic modulation of tumor tolerance should be evaluated in human trials.

Osmolal excretion after open heart surgery.

Water and osmolal balance was investigated during the peri-operative period in twenty unselected adult patients presenting for open heart surgery. On the day before surgery the mean urine output was 1.13 litres/sq m/24 hours and osmolal output 430 mOs/sq m/24 hours. Using a haemodilution cardiopulmonary bypass technique, patients received 2.62 litres/sq m and 792 mOs/sq m in the operating room. The pattern of excretion of this water and solute load was identified. Patients were still in positive balance on the day following surgery despite a considerable diuresis, with solute retention exceeding water retention.