A previous iGrow article, The Many Shades of Lameness looked at detection of lameness in feedlot and pasture cattle. What are the processes that contribute to these cases of lameness? One way to classify the various cause of lameness in cattle is to group them into two different categories: bacterial infection and injury. Some lameness cases will bridge these two classifications: sometimes lameness-causing infections are the direct result of injuries. This iGrow article will focus on causes of lameness associated with infections.
Footrot is perhaps the most common infectious cause of lameness in feedlot and pasture cattle. The technical term for footrot is “infectious pododermatitis”. Loosely translated, this means “inflammation of the skin and deeper tissues in the area of the hoof”. Footrot is usually caused by the bacteria Fusobacterium necrophorum, but other bacteria can be involved as well. All of these bacterial species are commonly found in soil and animal manure. This infection involves the area between the toes rather than the hoof itself. When the protective barrier of the skin is breached by these bacteria due to constant wet conditions or by abrasions, the bacteria causes a painful, necrotic infection between the toes.
If footrot is the most common infectious cause of lameness, hairy heel warts are the lameness cause getting the most recent attention in beef cattle circles. Hairy heel warts (“papillomatous digital dermatitis” is the medical term) have long been recognized as a significant problem in dairy cattle, but in recent years the problem has manifested itself in feedlot cattle as well. This is a very contagious condition, but how the disease starts in an animal is a bit unclear. Bacteria in the spirochete family can be demonstrated in the characteristic warts of this disease, but there may be other factors that enable the infection to take hold.
Any of the joints of the bovine limb potentially could harbor joint infections; however the most common joint affected by infection is the coffin joint—the lowest joint of the limb right at the hoof wall. Penetrating foreign objects can cause infection here, but a more common cause of coffin joint infections in cattle is a footrot infection that is not adequately treated. Infection spreads from the space in between the toes to penetrate the joint. An infectious agent often associated with joint infections is Mycoplasma bovis. In feedlot calves, this bacteria typically enters the bloodstream following an infection in the lungs, where it may have been the cause of signs of respiratory disease or may have been subclinical. While swollen, painful joints are apparent outwardly, Mycoplasma bovis actually infects the structures around the joints such as tendon sheaths rather than the joint space itself.