By Dörte Döpfer, DVM, MSc., Ph.D., and Arturo Gomez, DVM, MSc, University of Wisconsin School of Veterinary Medicine
Digital dermatitis (DD), also known as hairy heel warts, is an infectious hoof disease that is highly contagious. When left unchecked, DD can cause painful ulcerations that often lead to lameness. While DD has been present in cattle for decades, its prevalence in beef cattle is underestimated and typically increases when cattle are housed at higher stocking densities.
The resulting lameness from DD is a welfare and comfort issue, and also results in economic losses, since cattle with severe acute DD lesions (M2 stage) are lame, tend to be less mobile and consume less feed. To achieve effective control of DD in the face of increased production demands, a slightly more sophisticated approach will be required than the current standard of care.
Common practices for controlling DD have been limited mostly to footbaths (primarily used in dairy cattle operations) for prevention and topical treatment of acute lesions, but with no clearly established guidelines for optimal management. Recently, though, an improved understanding of the epidemiology of the disease has led to more effective ways to manage and even decrease the level of the disease within herds.
How DD takes hold
Digital dermatitis is multifactorial, with a strong bacterial component. The primary culprit is Treponema spp., bacteria that can exist in both active and cystic (dormant) forms. Typical progression of the disease includes:
• Acute (ulcerative) M2; and
• Chronic stages.
Once the disease has infected the animal, it is extremely difficult to eliminate. Chronic DD leads to proliferation of the affected areas (heel warts) that become reservoirs of infection for other cattle; blocky claws (abnormal claw conformation), weight loss and muscle atrophy can all be consequences of long-lasting lameness. It is important, therefore, to focus on preventing new infections and decreasing the duration of acute (ulcerative) M2 cases. These lesions most commonly occur at the skin-horn border, particularly in hind feet.
Ways to enhance disease resistance include: improving hygiene, re-assessing stocking densities, avoid grouping infected cattle with healthy cattle, and screening cattle for DD lesions. In addition, there is merit to providing cattle with an adequate supply of effective trace minerals. Our recent research has shown that supplementing Holstein steers with a specific combination of complexed and inorganic trace minerals resulted in 1) a trend toward fewer, painful M2 lesions and 2) a trend toward decreased size of DD lesions. Animals supplemented with the specific combination of complexed and inorganic trace minerals experienced a 45.5% reduction in M2 lesions, compared to animals fed the Control diet (only inorganic trace minerals). Improving disease resistance and lowering the prevalence of DD in this way could be particularly advantageous in cattle that are not handled on a regular basis, such as pastured cattle and beef cattle in feedlots.
Monitoring, prevention and hope for the future
Oftentimes, DD can cause changes in the shape and structure of an infected foot. In addition, within feedlots, certain pens tend to be high-prevalence pens because of the origin of mixed groups of cattle, the breed of cattle (particularly Holstein cross-bred cattle are affected), poor hygiene leading to high infectious pressure, re-grouping of cattle and high stocking density. In the Northern Hemisphere, the highest prevalence of DD is usually seen during the summer months, about 60 days prior to harvest, but can vary depending on climate and weather. The detection of DD requires routine and systematic inspections by workers who must be trained to recognize the disease at its various stages.
Solutions to DD depend on long-term prevention and control measures. This includes monitoring cattle for the presence of DD to understand the highest prevalence in relation to days on feed. A prevention program should be initiated 60 to 90 days prior to the time when the disease typically first appears.
As we move forward, research about the dynamics of DD will continue. More information will be generated on how activity and locomotion scoring can be used to assess disease severity, as well as estimates of the economic losses. We also continue to explore the genetic component of DD, all of this in the hope of finding better ways to help producers improve the performance and well-being of their herds.