Efficacy of quaternary ammonium salt-based disinfectant or chelated copper-zinc footbath solution in the treatment of digital dermatitis on one research dairy farm in Taiwan.

BACKGROUND: Footbaths can be used to manage digital dermatitis (DD), a common cause of lameness in dairy cattle. Copper sulfate and chelated copper-zinc (CZS) solutions in footbaths are potentially harmful to the environment. HYPOTHESIS/OBJECTIVES: To determine if a quaternary ammonium salt-based disinfectant (QASD) footbath is as effective as a chelated CZS solution in controlling DD in dairy cows. ANIMALS: Fifty-one lactating Holstein cows were randomly assigned to one of two treatment groups, with DD status based on the M-stage scoring system and locomotion score balanced between treatment groups. MATERIALS AND METHODS: The groups were treated with a 1% QASD or a 2.5% chelated CZS. Footbaths were performed once per week for 15 weeks. Logistic regression was used to analyse clinical improvement. All cows received appropriate medical treatment for DD and other hoof diseases. RESULTS: Clinical improvement rates were 67% in the QASD group and 38% in the CZS group (p = 0.03). Logistic regression analysis showed that the odds (95% confidence interval) for clinical improvement rate in the CZS group were 0.30 (0.095-0.948) times that of the QASD group (p = 0.04). The M0 score in the QASD and CZS groups increased significantly (p < 0.05) at the end of the 15 week study period. In the QASD group, the proportion of M2, M3 and M4 scores were significantly decreased (p < 0.05). CONCLUSION AND CLINICAL RELEVANCE: Over a 15 week period, QASD for footbathing was associated with a lower prevalence of active DD lesions than when using CZS.

The role of vanilloid receptor type 1 (TRPV1) in hyperalgesia related to bovine digital dermatitis.

Bovine digital dermatitis is a contagious and chronic disease affecting the digits of dairy cattle worldwide. Tissue degradation may alter ionic channels and further activate vanilloid channels, more specifically the vanilloid receptor type 1 (TRPV1) that can generate and modulate hyperalgesia in cows affected with bovine digital dermatitis. The aim of this pilot study was to identify and quantify TRPV1 channels in dairy cows presenting with different stages of bovine digital dermatitis and compare these data according to the disease evolution and degree of hyperalgesia described in previous studies. Biopsies were taken from 15 lactating Holstein cows (23 lesions), and immunochemistry was performed to identify the number of TRPV1 fibers in the 4 M-stages of digital dermatitis and the control group. This pilot study had 5 experimental groups, M1 (5 samples), M2 (5 samples), M3 (4 samples), M4 (4 samples), and the control group (5 samples), with inclusion criteria was the presence of a bovine digital dermatitis lesion in at least one digit. The pilot results demonstrate an increase in expression of TRPV1 receptors in group M4 in comparison with the other groups. Bovine digital dermatitis may cause an increase in expression of TRPV1 receptors in the chronic stages of the disease, possibly contributing to the hyperalgesia described in affected animals; nevertheless, further research is needed to define this relation.

Interobserver agreement of digital dermatitis M-scores for photographs of the hind feet of standing dairy cattle.

Digital dermatitis (DD) is the leading infectious cause of lameness in dairy cattle, and it affects their welfare and productivity worldwide. At the herd level, DD is often assessed while cows are standing in a milking parlor, and lesions are most commonly evaluated using the M-score. The objective of this study was to examine the interobserver agreement for M-scores of the feet of standing cattle, based on digital color photographs of dairy cattle hind feet. A total of 88 photographs and written descriptors of the M-score were sent to 11 scorers working at 10 different institutions in 5 countries. The scorers received no formal training immediately before scoring the photographs; however, all regularly used the M-score to score DD. The answers for 36 photographs were excluded from the analysis because the photograph either had more than 1 M-stage as mode or not all scorers assigned an M-score to it. The M-scores of the 11 scorers from 52 photographs were available for analysis. Interobserver agreement was tested using Gwet's agreement coefficient (AC1) and the mode was assumed correct. Overall, moderate agreement emerged for the M-score (AC1 = 0.48). For the individual M-stages, almost perfect agreement existed for M0 (AC1 = 0.99), M1 (AC1 = 0.92), and M3 (AC1 = 0.82), and substantial agreement for M2 (AC1 = 0.61), M4 (AC1 = 0.65), and M4.1 (AC1 = 0.71). This outcome indicates the degree of individual variation in M-scoring in this context by unstandardized, experienced European observers, particularly for the M2, M4, and M4.1 stages. Standardized training is likely to improve the consistency of M-scoring and thus the generalizability of future DD research results on this important endemic disease.

Inter-observer agreement between two observers for bovine digital dermatitis identification in New Zealand using digital photographs.

AIMS: To assess the inter-observer agreement for detecting bovine digital dermatitis (BDD) lesions in digital colour photographs of the hind feet of cows, which had been taken while the animals were standing to be milked, between two trained observers. METHODS: Thirty-six photographs were selected from a total of 184 photographs held by the first author (R1), who had classified them as negative (n=11) or positive (n=25) for BDD. They were delivered to a technician (R2) who had previously visually inspected cattle for BDD lesions, and who then recorded the photographs as being either BDD-positive or BDD-negative. The percentage agreement between R1 and R2, and two other inter-observer agreement statistics, Cohen's κ and Gwet's first-order chance correction agreement coefficient (AC1), were calculated. The cumulative membership probabilities of Cohen's κ and Gwet's AC1 were then calculated for different benchmark ranges of κ. RESULTS: The percentage agreement between R1 and R2 was 33/36 (92%), Cohen's κ was 0.80 (95% CI=0.57-1.0) and Gwet's AC1 was 0.86 (95% CI=0.69-1.0). Based on the cumulative membership probabilities for Gwet's AC1, there was 75% probability that the two observers had almost perfect agreement (κ≥0.81). For both Cohen's κ and Gwet's AC1, there was >95% probability that the two observers had at least substantial agreement (κ≥0.61). CONCLUSIONS: The two trained observers had at least substantial agreement in identifying from a digital photograph as to whether BDD lesions were present or absent. Therefore results from the two could be used interchangeably. CLINICAL RELEVANCE: Visual assessment for BDD lesions in the milking parlour can be subjective. However a high agreement between these two trained BDD inspectors means BDD prevalence reported from different regions in New Zealand by these two can be directly compared.

Experimental Transmission of Bovine Digital Dermatitis to Sheep: Development of an Infection Model.

Digital dermatitis is an infectious cause of lameness primarily affecting cattle but also described in sheep, goats, and wild elk. Digital dermatitis is a polymicrobial infection, involving several Treponema species and other anaerobic bacteria. Although the exact etiology has not been demonstrated, a number of bacterial, host, and environmental factors are thought to contribute to disease development. To study host-bacterial interactions, a reproducible laboratory model of infection is required. The objective of this study was to demonstrate key aspects of bovine digital dermatitis lesions in an easy-to-handle sheep model. Crossbred sheep were obtained from a flock free of hoof disease. Skin between the heel bulb and dewclaw was abraded before wrapping to emulate a moist, anaerobic environment. After 3 days, abraded areas were inoculated with macerated lesion material from active bovine digital dermatitis and remained wrapped. By 2 weeks postinoculation, experimentally inoculated feet developed erosive, erythematous lesions. At 4 weeks postinoculation, microscopic changes in the dermis and epidermis were consistent with those described for bovine digital dermatitis, including erosion, ulceration, hyperkeratosis, ballooning degeneration of keratinocytes, and the presence of neutrophilic infiltrates. Silver staining of lesion biopsy sections confirmed that spirochetes had penetrated the host epidermis. The model was then perpetuated by passaging lesion material from experimentally infected sheep into naïve sheep. This model of bovine digital dermatitis will allow for future novel insights into pathogenic mechanisms of infection, as well as the development of improved diagnostic methods and therapeutics for all affected ruminants.

A clinical and histopathological comparison of the effectiveness of salicylic acid to a compound of inorganic acids for the treatment of digital dermatitis in cattle.

Bovine digital dermatitis (DD) is a painful infectious disease, causing lameness, reduced animal welfare, and production losses in dairy herds. The main factors contributing to DD are an infection with Treponema spp. and poor hygiene. Topical treatment has primarily consisted of antibiotics; however, the demand for effective nonantibiotic alternatives is increasing. The objective was to evaluate the performance of 3 nonantibiotic topical treatments (salicylic acid and a compound of inorganic acids in a 20% solution and in a dry form) on DD in a commercial dairy herd. Within the 30-d test period, 42 DD lesions on 33 Holstein cows were assigned to receive 1 of the 3 treatments. Lesions were biopsied before and after treatment and were clinically evaluated 5 times. Improved lesions were clinically defined as either healed (regeneration of the skin) or healing (dry lesions covered by a scab). Unhealed lesions were defined as either active [with a raw, moist, strawberry-like (granulating) surface] or mature (with a raised papillomatous appearance). The effectiveness of treatment was evaluated histopathologically using the following scores: 0 (no spirochetes present), 1 (small number of spirochetes present in the epidermis), 2 (moderate number of spirochetes present and reaching an intermediary level in the epidermis), and 3 (large number of spirochetes present and reaching the deepest part of the epidermis or the superficial dermis). The improvement rate was 10/14 (71%) for salicylic acid, 11/15 (73%) for the inorganic acid solution, and 8/13 (62%) for the inorganic acid powder. The analysis showed no difference among treatments. The association between clinical score and histopathological score was determined by an odds ratio. The odds ratio of a healed lesion having spirochetes in the epidermis was 0.58 and that of an active DD lesion having spirochetes in the epidermis was 26.5.

Evaluation of agreement among digital dermatitis scoring methods in the milking parlor, pen, and hoof trimming chute.

Digital dermatitis (DD) is the most common infectious foot lesion affecting welfare and productivity of dairy cattle. The key to DD control programs is routine and frequent identification of DD lesions. The objective was to evaluate accuracy of detecting and scoring DD lesions in 3 milking parlor designs and in 3 alternative settings compared with scoring in the hoof trimming chute as reference. A total of 552 cows and 1,104 hind feet from 17 freestall farms were scored by 1 observer in the milking parlor and in 1 other setting: pen, headlocks, or management rail. After being scored in the milking parlor and at least 1 other setting, cows were examined in the hoof trimming chute, considered the gold standard. In every setting, all hind feet were inspected visually using a flashlight and without prior washing of feet. Agreement of the scoring settings was assessed using the 5 M-stage scoring system and a dichotomous absence (M0 or M0/M1) or presence (M1 to M4.1 or M2 to M4.1) system. At trimming chute inspection, 44% of feet had a DD lesion, with estimates of 11, 5, 2, 10, and 16% for M1, M2, M3, M4, and M4.1 lesions, respectively. Apparent DD foot-level prevalence at the milking parlor, pen, management rail, and headlocks was 28, 22, 16, and 22%, respectively. M-stages were less discernible in the pen, management rail, and headlocks (apparent prevalence of M1, M2, M3, and M4.1 was ≤1%) compared with the trimming chute and milking parlor. Agreement beyond chance between any scoring setting and trimming chute scoring ranged from 0.48 to 0.70 for the dichotomous scoring system (absence = M0/M1 vs. presence = M2 to M4.1). Diagnostic test performance varied greatly among DD scoring settings but, in general, it had low sensitivity (<70%) and high specificity (>93%) for detecting any DD lesion. Agreement and test characteristics were not affected by the type of milking parlor. Although the milking parlor and headlocks were the most reliable settings in which to detect DD, none of the settings were reliable enough to replace inspection of feet in the trimming chute. However, scoring the presence or absence of DD in the milking parlor, pen, management rail, and headlocks could be used to estimate within-herd DD prevalence, to improve DD surveillance through routine monitoring, and to evaluate effects of interventions at the farm level.

Prevalence of digital dermatitis in young stock in Alberta, Canada, using pen walks.

Digital dermatitis (DD), an infectious bacterial foot lesion prevalent in dairy cattle worldwide, reduces both animal welfare and production. This disease was recently identified in replacement dairy heifers, with implications including increased risk of DD and decreased milk production in first lactation, poor reproductive performance, and altered hoof conformation. Therefore, a simple and effective method is needed to identify DD in young stock and to determine risk factors for DD in this group so that effective control strategies can be implemented. The objectives of this study were to (1) determine prevalence of DD in young stock (based on pen walks); and (2) identify potential risk factors for DD in young stock. A cross-sectional study was conducted on 28 dairy farms in Alberta, Canada; pen walks were used to identify DD (present/absent) on the hind feet of group-housed, young dairy stock. A subset of 583 young stock on 5 farms were selected for chute inspection of feet to determine the accuracy of pen walks for DD detection. Pen walks as a means of identifying DD lesions on the hind feet in young stock had sensitivity and specificity at the animal level of 65 and 98%, with positive and negative predictive values of 94 and 83%, respectively, at a prevalence of 37%. At the foot level, pen walks had sensitivity and specificity of 62 and 98%, respectively, with positive and negative predictive values of 92 and 88%, respectively, at a prevalence of 26%. Pen walks identified DD in 79 [2.9%; 95% confidence interval (95% CI): 2.3-3.6%] of 2,815 young stock on 11 (39%; 95% CI: 22-59%) of 28 farms, with all 79 DD-positive young stock ≥309 d of age. Apparent within-herd prevalence estimates ranged from 0 to 9.3%, with a mean of 1.4%. True within-herd prevalence of DD in young stock, calculated using the sensitivity and specificity of the pen walks, ranged from 0 to 12.6%, with a mean of 1.4%. On the 11 DD-positive farms, the proportion of young stock >12 mo of age with DD lesions was 9.9% (95% CI: 7.8-12.0%). Multilevel logistic regression was used to assess associations with potential risk factors for DD lesions, including age, leg cleanliness, and lactating herd DD prevalence. Presence of DD in young stock increased as their age increased and was associated with increased prevalence of DD in the lactating herd. Pen walks can be used to identify specific young stock with DD or groups where management practices can be implemented to prevent disease proliferation and transmission.

Validation of the M-stage scoring system for digital dermatitis on dairy cows in the milking parlor.

A high prevalence of digital dermatitis (DD) and the benefits of early topical treatment highlight the need for simple tools for routine DD detection. The objective of this study was to determine the accuracy of scoring DD lesions using the 5 M-stage scoring system in the milking parlor compared with the trimming chute as the gold standard. Three observers inspected 3,585 cows and 6,991 hind feet from 9 farms in the milking parlor using a mirror (glued to a plastic kitchen spatula) and a headlamp, followed by inspection in a trimming chute within 5 d. Interobserver agreement for scoring DD in various settings was ≥82% (kappa >0.74; weighted kappa >0.76). At trimming chute inspections, 68% of cows had at least 1 DD lesion, 19% had 1 hind leg affected, and 49% had both hind legs affected. Within-herd DD prevalence ranged from 16 to 81% of cows affected. True within-herd prevalence was 2, 6, 0, 36, and 14% for M1, M2, M3, M4, and M4.1 lesions, respectively. At the foot level, DD prevalence was the same (58%) in the milking parlor and trimming chute inspection, but distribution of M-stages differed. Milking parlor inspection as a means of identifying the presence of DD lesions had a sensitivity of 92% and specificity of 88%, with positive and negative predictive values of 91 and 89%, respectively. Agreement between milking parlor and trimming chute inspections was 73% (kappa = 0.59, weighted kappa = 0.65) for the 5 M-stage scoring system and 90% (kappa = 0.80) if only the presence of a lesion was noted. Test characteristics varied greatly among M-stages, with the highest sensitivity for detecting M4 (82%) and M2 (62%) lesions, and the lowest for detecting M4.1 (20%), M1 (7%), and M3 (0%) lesions. In the milking parlor, 20% of M2 lesions were misclassified as M4.1, 8% of M4 lesions were misclassified as M0, and 68% of M4.1 lesions were misclassified as M4. The majority (87%) of DD lesions were located between the heel bulbs; 10 and 2% of DD lesions affected the interdigital space and the front of the foot, respectively. The sensitivity to detect the presence of a lesion when it occurred between the heel bulbs was 93%, but <67% if it occurred elsewhere on the foot. We concluded that inspection of the rear feet in the milking parlor was an inexpensive and simple method of detecting and scoring DD lesions. If the objective is to determine herd-level DD prevalence and routine monitoring, this method was adequately reliable. However, if the objective is to follow up DD in cows with history of interdigital hyperplasia or to detect M1 or M4.1 lesions, this method was not sufficiently reliable. Although DD scoring in the milking parlor as a routine practice should facilitate early detection, prompt treatment interventions, and herd monitoring, it was not sufficiently reliable to replace definitive identification of M-stages in the trimming chute.

A novel approach to probe host-pathogen interactions of bovine digital dermatitis, a model of a complex polymicrobial infection.

BACKGROUND: Polymicrobial infections represent a great challenge for the clarification of disease etiology and the development of comprehensive diagnostic or therapeutic tools, particularly for fastidious and difficult-to-cultivate bacteria. Using bovine digital dermatitis (DD) as a disease model, we introduce a novel strategy to study the pathogenesis of complex infections. RESULTS: The strategy combines meta-transcriptomics with high-density peptide-microarray technology to screen for in vivo-expressed microbial genes and the host antibody response at the site of infection. Bacterial expression patterns supported the assumption that treponemes were the major DD pathogens but also indicated the active involvement of other phyla (primarily Bacteroidetes). Bacterial genes involved in chemotaxis, flagellar synthesis and protection against oxidative and acidic stress were among the major factors defining the disease. CONCLUSIONS: The extraordinary diversity observed in bacterial expression, antigens and host antibody responses between individual cows pointed toward microbial variability as a hallmark of DD. Persistence of infection and DD reinfection in the same individual is common; thus, high microbial diversity may undermine the host's capacity to mount an efficient immune response and maintain immunological memory towards DD. The common antigenic markers identified here using a high-density peptide microarray address this issue and may be useful for future preventive measures against DD.

The effect of digital dermatitis on hoof conformation.

Digital dermatitis (DD) is the most prevalent cause of lameness of infectious origin in cattle. However, little is known about the effects of DD on hoof conformation (HC) during the clinical disease. The objectives of the present study were to (1) evaluate the changes in HC observed in feet affected with clinical DD lesions and (2) investigate the temporal relationship between DD and heel horn erosion (HHE). A longitudinal study was carried out including a cohort of 644 Holstein heifers. Digital dermatitis, HC, and presence of HHE in the rear feet of each heifer were assessed during a period of 6 mo. A total of 1,979 feet evaluations were included in the data set, of which 157 corresponded to feet presenting DD lesions >20mm [mean (SD) size of 27.2 (8.2) mm]. Age, days of pregnancy, hip height, and girth circumference were also recorded at cow level. Significant HC changes were observed in DD-affected feet. Results standardized to a period of 90d of follow-up showed an increase in heel height [mean (95% CI) 3.4 (2.5, 4.4) and 2.8 (2.0, 3.7) mm] and claw angle [0.8 (0.2, 1.4) and 1.4 (0.7, 2.0) degrees] of the medial and lateral claws, respectively. In addition, an increase in depth of the interdigital cleft [3.2 (2.7, 3.7) mm] and on debris accumulation [14% (7, 21) of feet] was also observed. Feet affected with clinical DD lesions also experienced a 46% point increase in the presence of severe HHE. In the short term, HC changes returned to normal levels when clinical cure of DD was achieved after topical treatment. In conclusion, significant HC changes occur in heifers affected by clinical DD before lameness symptoms are detected. The transformation of the heel area in feet affected by DD likely promotes the creation of a local environment that favors the persistence of the disease and the occurrence of severe HHE. To avoid further hoof damage, active surveillance and early intervention to reduce HC changes are recommended to improve DD control programs. Successful restoration of HC can be achieved upon clinical cure of DD. The long-term effects in lifetime performance of the HC changes due to DD remain to be further investigated.

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.

Evaluation of selected risk factors for different stages of digital dermatitis in Dutch dairy cows.

Digital dermatitis (DD) is a painful infectious disease in dairy cattle that causes ulcerative lesions of the skin just above the coronary band, mainly of the hind legs. Estimates for DD prevalence at cow level in the Netherlands range from 20% to 25%. In this study, risk factors for the various stages of DD were identified and quantified. The hind legs of 6766 cows on 88 farms were scored by trained interns, using the M-scoring system (M0-M4.1). Farms in this study were a convenience sample, based on the prevalence of DD as recorded at the latest herd trim, geographical location and willingness of the farmers to participate. A survey with questions about cow environment and herd management was conducted by the intern at the day of scoring. The data were collected between August 2017 and January 2018. DD was found on 38.6% of the scored legs; 49.8% of the cows had DD on at least one leg and M4 was the most frequent stage (20.9%). Not removing manure on a regular basis resulted in lower odds for M2, M4 and M4.1 compared to cleaning by automatic scrapers ten times a day or more (odds ratio [OR]= 0.16, 0.49 and 0.18, respectively). The odds for M2 and M4 lesions were higher in cows aged 3-5 years than in first-calved cows (OR> 1.5 and > 1.7, respectively). Rubber flooring in the passageways resulted in lower odds for both M1 and M2 (OR, 0.06 and 0.32, respectively). Prophylactic use of footbaths treatment with an alternative active compound resulted in significant higher odds for M4 lesions than formalin and a combination of formalin and copper sulphate (OR= 1.69 and 2.04 respectively). The odds for an M4.1 lesion were lower in cows from smaller herds (n = 50-100) compared to large herds (n >100; OR= 0.67).

Analysis of foot health records from 17 confinement dairies.

Foot health records are useful in monitoring the degree of lameness within dairy herds and, perhaps more importantly, providing insight into the underlying factors causing lameness. A database containing the incidence of foot lesions on large confinement dairy operations is largely unavailable but could prove useful to demonstrate the importance of collecting and analyzing foot lesion data to reduce lameness. Our objective was to merge foot lesion records from several dairy herds and establish a database to demonstrate how to use such data to better understand when and why foot lesions occur as an important means to manage lameness in dairy herds. The database consisted of 12 mo of records from 17 dairies (14 freestall, 1 combination dirt lot and freestall, 2 dirt lot) representing 58,155 cows from herds ranging in size from 631 to 9,355 animals in 9 states from the United States and 2 herds located in the Southern Hemisphere. Data were partitioned and analyzed as 2 separate data sets: (1) herds recording only lame events (cows lame when examined; n=8), and (2) herds recording both lame and routine trim events (n=9). Data were analyzed using PROC FREQ (SAS Institute Inc., Cary, NC) and significance was determined using Chi-square. White line disease, sole ulcer, toe ulcer, digital dermatitis, and foot rot comprised 93 and 40% (excluding routine trim with no lesion, 55%) of lesions for herds recording only lame events and those recording lame and trim events, respectively. Ratio of infectious to noninfectious lesions decreased with increasing lactation number in both data sets. Digital dermatitis and foot rot were greatest in the first 60 d in milk and differed across lactation number. Noninfectious lesions were greatest following summer heat stress, whereas infectious lesions were greatest during the coolest quarter of the year. In conclusion, analysis of the foot health data from these dairies demonstrates that (1) infectious lesions of the foot skin and soft tissues predominate in early lactation and during cooler months of the year, and (2) noninfectious lesions predominate during the 3 mo following summer heat stress and their distribution follows a typical lactation curve.

Randomized clinical trial of tetracycline hydrochloride bandage and paste treatments for resolution of lesions and pain associated with digital dermatitis in dairy cattle.

Digital dermatitis is an infectious disease that causes lameness in dairy cattle, a primary welfare concern of the dairy industry. One of the common treatments for this painful hoof disease is through the application of an antibiotic bandage that must be removed following treatment. The objectives of this randomized clinical trial were to determine if topical application of tetracycline hydrochloride in a paste would be as therapeutically effective for the treatment of digital dermatitis as a powdered form of tetracycline hydrochloride held in place by a bandage, and to quantify pain associated with digital dermatitis lesions. Two hundred and fourteen Holstein cow hooves with digital dermatitis lesions were randomly assigned to 1 of 3 treatments: a tetracycline hydrochloride paste, tetracycline hydrochloride powder held in place with a bandage for 2 d, or a negative (untreated) control. Lesions were examined at 2 time periods: 3 to 7 d posttreatment and 8 to 12 d posttreatment to determine healing rates. Nociceptive thresholds were measured using a pressure algometer to quantify the pain at the lesion site. The tetracycline hydrochloride paste was as effective as the powdered bandage treatment in terms of healing rates, with 47.4 and 57.1% hooves healed at 8 to 12 d posttreatment, respectively. Both treatments were more effective than the control, in which no lesions healed 8 to 12 d following initial examination. Mean (±SE) nociceptive thresholds for active, healing, and healed lesions differed, with limb-withdrawal response occurring at 7.45 (±0.67) kg, 12.84 (±1.85) kg, and censored to 25 kg (maximum value of algometer) of force applied, respectively. However, active lesions were not consistently associated with pain, as maximum force was tolerated when applied to 19% of active lesions, perhaps due to variability in stoicism between individual cattle or due to changes in pain during the progression of infection. In conclusion, tetracycline hydrochloride paste was as effective as tetracycline hydrochloride bandage, eliminating the need for bandage removal following treatment application. Digital lesions can be painful during both active and healing stages, suggesting the need for treatment and husbandry interventions for pain mitigation.

Transmission and lesion progression of treponeme-associated hoof disease in captive elk (Cervus canadensis).

Treponeme-associated hoof disease (TAHD) is a debilitating disease of free-ranging elk (Cervus canadensis) in the northwestern U.S. While treponemes are associated with lesions, the etiology and transmissibility between elk are unknown. Our objective was to determine whether the disease can be environmentally transmitted to captive elk. Four individually housed treatment elk and 2 control elk were challenged with soil mixed with inoculum prepared from free-ranging elk hooves from TAHD-positive elk or autoclaved hooves from normal elk, respectively. The inoculum for each group was applied to the interdigital space and added to pre-existing soil in each pen. Eight challenges were conducted at 1-4-week intervals and lesion development was assessed during a 138-day challenge period that was followed by a 170-day monitoring period to document lesion progression. All treatment elk, but no control elk, developed gross and histologic lesions consistent with TAHD. Treponema phylotypes similar to those in bovine digital dermatitis in cattle were detected using 16S rRNA gene amplicon sequencing from lesions in all treatment elk, but no control elk, during the challenge period. Lesions progressed from ulcerations in the interdigital space to extensive ulceration and underrunning of the hoof capsule by 35 and 173 days following the initial inoculation, respectively. Lameness in treatment elk was correlated with lesion development (R = 0.702, p≤0.001), and activity of infected elk was reduced during the challenge (p≤0.001) and monitoring periods (p = 0.004). Body condition was significantly lower in treatment than control elk 168 days following the initial inoculation (p = 0.05) and at each individual elk's study endpoint (p = 0.006). Three of 4 treatment elk were euthanized when they reached humane endpoints, and one elk recovered. These results provide direct evidence that TAHD is a transmissible infectious disease in elk. As such, actions that reduce transmission risk can support disease management and prevention.

Broad-spectrum infrared thermography for detection of M2 digital dermatitis lesions on hind feet of standing dairy cattle.

Low-effort, reliable diagnostics of digital dermatitis (DD) are needed, especially for lesions warranting treatment, regardless of milking system or hygienic condition of the feet. The primary aim of this study was to test the association of infrared thermography (IRT) from unwashed hind feet with painful M2 lesions under farm conditions, with lesion detection as ultimate goal. Secondary objectives were to determine the association between IRT from washed feet and M2 lesions, and between IRT from unwashed and washed feet and the presence of any DD lesion. A total of 641 hind feet were given an M-score and IRT images of the plantar pastern were captured. Multivariable logistic regression analyses were done with DD status as dependent variable and maximum infrared temperature (IRTmax), lower leg cleanliness score and locomotion score as independent variables, and farm as fixed effect. To further our understanding of IRTmax within DD status, we divided IRTmax into two groups over the median value of IRTmax in the datasets of unwashed and washed feet, respectively, and repeated the multivariable logistic regression analyses. Higher IRTmax from unwashed hind feet were associated with M2 lesions or DD lesions, in comparison with feet without an M2 lesion or without DD, adjusted odds ratio 1.6 (95% CI 1.2-2.2) and 1.1 (95% CI 1.1-1.2), respectively. Washing of the feet resulted in similar associations. Dichotomization of IRTmax substantially enlarged the 95% CI for the association with feet with M2 lesions indicating that the association becomes less reliable. This makes it unlikely that IRTmax alone can be used for automated detection of feet with an M2 lesion. However, IRTmax can have a role in identifying feet at-risk for compromised foot health that need further examination, and could therefore function as a tool aiding in the automated monitoring of foot health on dairy herds.

Infection dynamics of digital dermatitis in first-lactation Holstein cows in an infected herd.

Digital dermatitis (DD) refers to painful lesions primarily affecting the skin in the interdigital region of dairy cattle. The purpose of this study was to evaluate the dynamics of DD in 39 cows, observed at approximately 3-d intervals, for the first 6 mo of lactation. Specifically, the study aimed at evaluating different levels of DD susceptibility in cows, identifying the bacterial colonization of the interdigital skin, and exploring the relationship between clinical DD diagnosis and laboratory findings. Three different susceptibility categories were identified for DD: 1=consistently healthy cow; 2=intermittently infected cow; and 3=consistently infected cow. Susceptibility categories were associated with age at calving. The average age at calving was 775 d (SD ±43.4), with the youngest heifer calving at age 669 d and the oldest heifer at 858 d. Advancing age at calving was associated with greater odds of being intermittently or consistently infected. This corresponded with an odds ratio of 2.02 over a period of 30 d. During the study period, 161 DD lesions were identified in 28 of the 39 cows (72%). Of those 28 cows, 13 cows were consistently infected. The remaining 11 of the 39 cows (28%) showed slight thickening of the skin with no pain (5 cows) and no signs of skin changes (6 cows). Histopathology and fluorescence in situ hybridization were possible to perform on 132 biopsy samples. A clinical diagnosis of DD was confirmed in 70% of the lesions by histopathology, and colonization of Treponema spp. Dichelobacter nodosus was found in 35 samples (29%).

Effectiveness of different footbathing frequencies using copper sulfate in the control of digital dermatitis in dairy cows.

Two experiments were conducted to test the effectiveness of different footbathing frequencies using CuSO4 in the control of digital dermatitis (DD) in groups of dairy cows with low and high DD prevalence in an endemically infected herd. During the study, groups of cows walked through allocated footbath solutions after milking on 4 consecutive milkings each week, 2 wk, or monthly, depending on treatment. The footbath solutions were changed either after 200 cows had passed through the footbath or within 24 h. All cows were scored weekly during milking for DD lesion stage on the hind feet using a 5-point nominal scale. A transition grade was assigned based on whether the DD lesions improved (1) or deteriorated or did not improve (0) from week to week, and was averaged for all cows in the group. Furthermore, from the longitudinal study data, all transitions between different DD lesion stages between the different time points were used in a discrete, first-order Markov chain (state transition matrix) model. In experiment 1, 70 Holstein-Friesian cows with DD lesions present on at least one of their hind feet were allocated to 1 of 2 footbath treatments for 14 wk: (1) 5% CuSO4 each week or (2) 5% CuSO4 every 2 wk. At the end of the study, no active DD lesions were observed in cows in either treatment group, but significantly more cows had no DD lesions (0.48 ± 0.097 vs. 0.24 ± 0.094) and fewer cows had lesions in the healing stage (0.52 ± 0.104 vs. 0.77 ± 0.090) for the weekly compared with the 2-wk footbathing regimen. The number of active DD lesions that the transition matrix model predicted over time was 3 and 8% for weekly and every 2 wk footbathing treatments, respectively. In experiment 2, 64 cows with no DD lesions on either of their hind feet were allocated to 1 of 2 footbath treatment regimens for 14 wk: (1) 5% CuSO4 every 2 wk or (2) 5% CuSO4 each month. At the end of the trial, significantly more cows had no DD (0.80 ± 0.088 vs. 0.65 ± 0.102) and fewer cows had DD lesions in the healing stage (0.20 ± 0.088 vs. 0.35 ± 0.102) in the every 2 wk regimen than in the monthly footbathing regimen. The number of active DD lesions that the transition matrix model predicted over time was low for both footbathing interventions (1 and 4%, respectively). Increasing the interval between footbaths does not appear the most appropriate mechanism for reducing CuSO4 usage.

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.