Actinomyces bovis is a branching, Gram-positive, rod-shaped bacterium of the genus Actinomyces.[1] It is the causative agent of lumpy jaw (actinomycosis) in cattle, and occasionally causes infections in humans.[2] A. bovis normally populates the gastrointestinal tract of healthy ruminants, but is opportunistic in nature and will move into tissues through ulcerations or abrasions of the mucosa to cause disease.[3] Disease occurs when there is physical damage to the tissue of the mouth, allowing the bacteria to colonize the deep tissue and bone, typically affecting the mandible and maxilla.[4] Actinomycosis is pathognomonic for abscesses containing "sulfur" granules, and appears as basophilic colonies with club-shaped reaction products on a histological preparation.[5][6] Lumpy jaw is commonly treated with broad-spectrum antibiotics with varying success,[7] and can be a major economic loss for producers in countries where it is endemic.[8] Because this organism is zoonotic, it is a human health concern and can cause granulomas, abscesses, skin lesions, and bronchopneumonia.[3]