Host Factors Impacting the Development and Transmission of Bovine Digital Dermatitis

This review provides insight on potential host-specific factors that increase individual susceptibility to infection and transmission of bovine digital dermatitis. Digital dermatitis is increasing in prevalence within herds worldwide and yields economic losses for producers and welfare issues for animals. A total of 34 relevant studies were reviewed based on the inclusion criteria. A decrease in susceptibility to disease was found in animals with specific genomic and hoof characteristics, thus citing the importance of sire selection when designing a breeding program. Animals with superior health status that lacked co-morbidities and mounted immune responses to infection were less likely to develop disease. Primiparous cattle and those in peak production were more likely to develop lesions, as were over-or-under-conditioned Holstein–Friesian breeds. Cattle with superior hoof conformation and gait were poor hosts for bacteria and therefore less likely to develop and spread infection. The lowest risk of transmission of digital dermatitis occurred during the dry period and post peak lactation and cattle with advanced lesions contributed to the persistence of the disease within a herd. It is hoped that this review will help producers design breeding and management programs for their herds, and help veterinarians advise clients on the subject.

Lesion Material From Treponema-Associated Hoof Disease of Wild Elk Induces Disease Pathology in the Sheep Digital Dermatitis Model

A hoof disease among wild elk (Cervus elaphus) in the western United States has been reported since 2008. Now present in Washington, Oregon, Idaho, and California, this hoof disease continues to spread among elk herds suggesting an infectious etiology. Causing severe lesions at the hoof-skin junction, lesions can penetrate the hoof-horn structure causing severe lameness, misshapen hooves, and in some cases, sloughed hooves leaving the elk prone to infection, malnutrition, and premature death. Isolated to the feet, this disease has been termed treponeme-associated hoof disease due to the numerous Treponema spp. found within lesions. In addition to the Treponema spp., treponeme-associated hoof disease shares many similarities with digital dermatitis of cattle and livestock including association with several groups of anaerobic bacteria such as Bacteroides, Clostridia, and Fusobacterium, neutrophilic inflammatory infiltrate, and restriction of the disease to the foot and hoof tissues. To determine if there was a transmissible infectious component to this disease syndrome, elk lesion homogenate was used in a sheep model of digital dermatitis. Ten animals were inoculated with lesion material and lesion development was followed over 7 weeks. Most inoculated feet developed moderate to severe lesions at 2- or 4-weeks post-inoculation timepoints, with 16 of 18 feet at 4 weeks also had spirochetes associated within the lesions. Histopathology demonstrated spirochetes at the invading edge of the lesions along with other hallmarks of elk hoof disease, neutrophilic inflammatory infiltrates, and keratinocyte erosion. Treponema-specific PCR demonstrated three phylotypes associated with elk hoof disease and digital dermatitis were present. Serum of infected sheep had increased anti-Treponema IgG when compared to negative control sheep and pre-exposure samples. Analysis of the bacterial microbiome by sequencing of the bacterial 16S rRNA gene showed a community structure in sheep lesions that was highly similar to the elk lesion homogenate used as inoculum. Bacteroidies, Fusobacterium, and Clostridia were among the bacterial taxa overrepresented in infected samples as compared to negative control samples. In conclusion, there is a highly transmissible, infectious bacterial component to elk treponeme-associated hoof disease which includes several species of Treponema as well as other bacteria previously associated with digital dermatitis.

Phenytoin: A promising non-antibiotic drug for the topical treatment of digital dermatitis in dairy cows

Background and Aim: Digital dermatitis (DD) is one of the most common causes of lameness in dairy cattle. It is seen in nearly all dairy herds across the world and has substantial welfare and economic implications. In this study, we aimed to investigate the efficacy of phenytoin sodium topical treatment on painful ulcerative stage of bovine digital dermatitis (BDD). Materials and Methods: In total, 45 Holstein-Friesian dairy cows with DD were randomly assigned to one of the three topical treatment trials (15 each): Saline solution (first treatment, negative control), chlortetracycline spray (second treatment, positive control), or phenytoin sodium powder (third treatment, positive control) (third treatment). On day 0 (pre-treatment) and on days 7, 14, 21, and 28 post-treatment, the response of DD-affected cows to the medications used was evaluated by measuring lesion depth and size, as well as the total clinical score (lameness, pain, and discomfort). Results: The cure rate in cows treated with phenytoin (86.66%) on day 28 was significantly improved compared to cows treated with either chlortetracycline (60%) or normal saline (6.66 %). Conclusion: Our findings highlight the superiority of phenytoin over the commonly used antibacterial agent, chlortetracycline, in the topical treatment of BDD, and subsequently suggest that phenytoin should be considered a suitable alternative treatment option for the treatment of BDD.

527 Late-Breaking: Objective Assessment of Behaviour, Pain, and Lameness Due to Digital Dermatitis in Beef Cattle

Digital dermatitis (DD) is an infectious disease affecting cattle feet causing ulcerative and necrotic skin lesions. Most lesions are painful when palpated, some cause lameness and significantly impact animal welfare and productivity. Our objectives were: to determine if changes in behaviour were associated with DD in cattle, to quantify pain associated with DD lesions, and to determine the relationship between pain sensitivity and lameness, and DD and lesion temperature. In total, 255 animals across three feedlots were enrolled. A subset of 120 animals were fitted with accelerometers to record behaviour. Cattle were scored for lameness (Step-Up Locomotion Scoring System), both hind feet scored for DD (M-stage scoring system), the pressure pain threshold of lesions determined using pressure algometry and lesion temperature using thermal images. Animals and feet were classified as DD absent or present. Further, DD present was divided into active or chronic. Behaviour, 5 to 2 days before DD identification was analyzed. Animals with DD ruminated 3% less daily compared to animals without DD (P < 0.05). Further, animals with active lesions ruminated 5% less daily (P < 0.05). Daily inactivity time was greater in animals with DD and the effect of day depended on type of lesion (P < 0.05). Feet without DD lesions withstood 5.6N more pressure (P < 0.001). Active lesions were most sensitive withstanding 8.1N less pressure and chronic lesions 4.1N less pressure than DD absent feet (P < 0.05). Moderate to severely lame animals withstood 3.1N less pressure than sound animals (P < 0.001). Median maximum temperature (MMT) was higher in feet with DD compared to those without (P < 0.001) with MMT being highest in active lesions (P < 0.05). In conclusion, rumination is depressed, and inactivity increased in DD affected animals. Both active and chronic lesions are painful, lame animals have a lower pain threshold and DD is associated with higher lesion temperatures.

144 The Epidemiology of Hoof-related Lameness in Western Canadian Feedlot Cattle

The epidemiology of hoof-related lameness (HRL) in western Canadian feedlots, with a focus on digital dermatitis (DD), was described and analyzed to help inform recommendations on lameness control and prevention in western Canadian feedlot cattle. The retrospective data in this study were accessed from 28 western Canadian feedlots that placed cattle in 2014–2018, inclusive. The total population for this study was 1,796,176 cattle, with an annual placement average of 12,830 cattle per feedlot. These data were accessed through iFHMS Consolidated Database, provided by Feedlot Health Management Services by TELUS Agriculture, and manipulated using Microsoft® Office Access 365 ProPlus and Microsoft® Office Excel 365 ProPlus. Epidemiological analyses determined that lameness accounts for 25.7% of all treatments in western Canadian feedlots. Of those treatments, 71.7% are localized to the hoof, corresponding to 18.6% of all treatments. The most common HRL diseases are infectious bovine pododermatitis [foot rot (FR)]; digital dermatitis (DD), also known as hairy-heel wart or strawberry foot rot; and toe-tip necrosis syndrome (TTNS). These diseases account for 89.6%, 7.9% and 2.4% of HRL, respectively. Between 2014 and 2018, HRL prevalence ranged between 1.93% and 3.09% of the population, with FR consistently having the highest prevalence and TTNS the lowest. HRL and DD were tested for their associations with several animal-level risk factors using © Ausvet 2021 Epitools software. The resultant crude, univariate odds ratio values, evaluated at 95% confidence, are summarized in Table 1. Based on this analysis, acquisition source has the largest influence on the odds of developing HRL and DD, followed by population size, and placement quarter. Using SAS® (Version 9.4, SAS Institute Inc, Cary, North Carolina) statistical software, these preliminary findings will be subjected to a multivariate statistical model, which will provide adjusted OR values and statistical significance for the data in this study.