Special Veterinary Pathology

ACTINOMYCOSIS

Synonym : Lumpy Jaw

Definition

• Actinonomycosis is infection caused by the organisms of the genus Actinomyces characterized by rarefying osteomyelitis and chronic granulomatous inflammation.

Etiology

• Gram +ve rod shaped anaorobes pleomorphic, non sporulating non motile
• Branching forms (Ray fungus)
• Actinomyces bovis –present in the mucosa of the mouth and pharynx

Incidence

• It is reported from most countries of the world and prevalent in India

Susceptibility

• Cattle mostly affected and it affects many species

Transmission

• Normal inhabitant of oral cavity
• Wounds in oral cavity caused by awns, hullscutting teeth or lesion caused by FMD predisposes for actinomycosis
• Necrosis produced by penetrating objects, set up necessary anaerobic conditions for the organism to grow and thrive.

Pathogenesis

• Organisms are lodged, it incites a granulomatous inflammation
• Around the colony of organisms, Indian club like structure is thought to be a product of immune reaction of host to invading organisms probably from macrophages.
• Peripheral to these neutrophils surrounds and beyond these histiocytes and epithelioid cells found
• Around this layer, lymphocytes, plasma cells and eosinophils accumulates and vascular fibrous tissue forms
• Purulent centres surrounded by granulation tissue displaces normal tissue
• The yellowish pus from abscess are referred to as 'sulphur granules' ( Bigger in size)
• Central part containing the Gram positive organisms
• Horses- Poll evil and fistulous withers

Gross lesions

• Lumpy jaw- Suppurative osteomyelitis of the mandible
• Maxilla and others areas - Rarely affected
• Infection from gums and periodontium produces actinomycotic periosteitis
• Medulla to be infected and cavity filled with granulation tissue containing nodules
• Softening and liquefaction occur and the pus gradually affects the cortex rarefying it and fistulae form
• Periosteum is irritated to form new subperiosteal bone (Involucrum) and leaving cavities and Fistulae
• Whole bone is destroyed.
• Extend into muscles, subcutaneous tissue, skin or mucous membrane
• Maxilla is affected, to the sinuses and to the dura matter
• Udder shows miliary nodules
• Pigs- Udder may be indurated and fibrosis with suppuration
• Lungs - Haematogenous infection
• Lymph glands also affected
• Preventing prehension and mastication
• Infection to oesophagus and abomasum gives rise to impaired digestion and diarrhoea

Microscopic lesions

• Around the colony of organisms, Indian club like structure is seen
• Accumulation of neutrophils, histiocytes and epithelioid cells are noticed.
• Sometimes, lymphocytes, plasma cells and eosinophils and vascular fibrous tissue are seen

Diagnosis

• Symptoms
• Stained pus smear
• Histopathological examination of lesion