Actinomyces bovis

Lumpy jaw (actinomycosis) in cattle can present itself in two main ways. One is as soft-tissue abscesses in the mouth and on the tongue. The other explains its common name, lumpy jaw, as A. bovis bacteria infect the mandibular bone, causing osteomyelitis[17] and the formation of periosteal new bone, giving it the classical lumpy jaw appearance.[18] It is caused by sharp objects, such as coarse feed materials or sticks, causing penetrative lesions in the mouth when ingested or by complication of periodontitis.[17][18] Deeper lesions are required to cause infections in the bone, while shallower lesions are more likely to cause mouth abscesses.[18] The bony lumps are usually not painful and can develop over weeks to months, causing facial distortion, dyspnea, and occasionally loose teeth.[17][18][19] The abscesses within the bony lumps or soft tissue commonly consist of purulent granulation tissue, often gritty in texture, surrounded by a fibrous capsule.[20]

Actinomycosis affecting the maxilla in a cow

To diagnose lumpy jaw, the fluids exuding from the bony lump or other abscesses are sampled or aspirated if the infection has not broken through the skin.[18] Tissue samples from the lesion can be examined by histopathology after being embedded in paraffin wax, cut into 4- to 5-mm sections, and stained with hemolysin and eosin stains.[17] The clubs could also be stained by carbol fuchsin with decolourisation by weak hydrochloric acid and counter-staining with methylene blue, Van Gieson's stain, or aniline gentian violet followed by treatment with alcohol.[20] A. bovis can be identified histologically by its basophilic colonies and club-shaped reaction product visible in neutrophilic granulomatous lesions.[17] The club-shapes, also called Spendore-Hoeppli proteins, seen on histological slides are the result of the bacteria being encased in a calcium-phosphate protein complex, as the host attempts to wall off the infection.[17] Another diagnostic feature is the presence of "sulfur" granules,[6] which is pathognomonic for actinomycosis.[17] These granules are small, yellow clumps of exudate that are visible to the naked eye with a similar appearance to grains of sulfur, and are mainly composed of bacterial filaments and host calcium phosphate.[17]

The efficacy of the clinical treatment for A. bovis lesions is not always successful,[8] but conventional treatment plans involving combinations of broad-spectrum antibiotics and concurrent administration of iodide solutions have demonstrated success in reducing the inflammation and spread of the lesion.[21] Initial treatment involves surgical debridement of purulent and soft-tissue lesions followed by daily cleaning and flushing of the infection site with saline and povidone-iodine solution, respectively, for about 1 week.[22] Treatment success has been noted individually for both potassium iodide oral solution,[23] and for intravenous sodium iodide,[24] as well as when used conjunctively.[25] However, frequent treatment with iodide may lead to toxicity, and monitoring for clinical signs of iodine toxicity should be included throughout the course of treatment.[26] Consequently, administration of iodide should be either reduced or discontinued if such signs of toxicity are observed.[26] Antibiotic combinations of intramuscular penicillin and streptomycin are commonly used for 5–7 days, and have been widely associated with treatment success.[22] Additional antibiotics such as oxytetracycline, florfenicol, and cloxacillin have also demonstrated sensitivity.[21][26]

Infiltration of A. bovis occurs following trauma and subsequent infection of the oral cavity.[21] Common causes of trauma to the oral mucosa include consumption of abrasive feed or foreign bodies (thorns, wire, etc.), or eruptions of cheek teeth.[21] Prevention advice focuses on avoiding coarse feed with suggestions such as softening feed with water.[27] Examination of feed structure is especially encouraged if the infection is widespread throughout the herd.[21]