Introduction

• Cause: disease process associated with a filamentous gram-positive, anaerobic or microaerophilic bacilli of the genus Actinomyces, phylum Actinobacteria.
• Signs: can range from non-specific findings such as lethargy and anorexia to visible masses, ulcer and/or sinus tracts that are most reported around the face and jaw. In ball pythons reported around the cloaca and hemipenis. Dyspnea and tachypnea may be noted in animals with pulmonary and/or pleural disease associated with actinomycosis.
• Diagnosis: bacteriologic identification of filamentous bacilli together with the presence of sulfur granules within affected tissue(s), or positive identification using molecular methods.
• Treatment: Actinomyces spp are typically sensitive to penicillin, amoxicillin, clindamycin and doxycycline. Treatment with high doses for a prolonged period is usually required. Other treatment modalities may be required depending on the location of infection and body system(s) affected.
• Prognosis: good to fair if disease is recognized early and followed by prompt and appropriate treatment(s); guarded to poor if infection is in a critical location or if disease is identified in later stages with significant tissue destruction and/or multiple sinus tract formation.

Pathogenesis

Etiology

• Bacteria of the genus Actinomyces, phylum Actinobacteria.
• Filamentous gram-positive, anaerobic, microaerophilic or facultative anaerobic bacilli.
• Actinomyces spp are considered part of the endogenous mucosal microbiome in many species:
  • Identified in the oral cavity of cats and in the oral, gastrointestinal, and urogenital mucosa of humans.
  • Bacteria in the phylum Actinobacteria have been identified in the gut microbiomes of various agamids.

Predisposing factors

General

• Poor husbandry and hygiene practices.
• Oral cavity lesions.
• Immunosuppression caused by drugs or other systemic disease process.

Specific

• Bites from other animals.
• Strenuous, repetitive and long-term breeding activity in male ball pythons (Python regius) suggested as a possible factor for the development of granulomatous mucosal disease syndrome in this species.

Pathophysiology

• Actinomycosis is typically caused by direct invasion of a tissue site by the bacteria.
• Hematogenous dissemination is considered rare.
• Organism typically form part of the endogenous mucosal microbiome in many species.
• Tissue invasion and subsequent infection occurs where these is a break in the normal mucosal or epithelial barrier:
  • Can occur due to trauma, or co-infection with another bacterial pathogen that inhibits host defenses or by reducing oxygen tension.
  • Presence of foreign bodies.
  • Chronic conditions that can result in immunocompromise.
• Intense inflammatory response is initiated by the host which is typically suppurative and granulomatous.
• Acute inflammatory phase may be observed, but the disease more frequently presents during the chronic phase of infection.
• Infection spreads contiguously, often resulting in draining sinus tracts and intense tissue fibrosis
• The bacterium typically forms sulfur granules within inflammatory tissue lesions:
  • Comprises of branching, filamentous Actinomyces and proteinaceous material.
  • Thought to be a mechanism to avoid and inhibit phagocytosis by host immune system.

Timecourse

• Variable.
• Clinical disease may not be noted for days to months after initial insult to a mucosal or epithelial barrier. Acute on chronic presentations may occur, eg rupture of a slowly expanding pulmonary abscess into the trachea.

Epidemiology

• Actinomyces spp are considered part of the endogenous flora of mucous membranes in many species:
  • Infection in the majority of cases is thought to arise from opportunistic entry of the bacteria into sterile areas of the body.
  • The organism has never been cultured from the environment.
• Transmission between animals is typically through bites.
• Infection theoretically can occur in animals of all ages and genders.
• Strenuous, repetitive and long-term breeding activity in male ball pythons (Python regius) suggested as a possible factor for the development of granulomatous mucosal disease syndrome in this species.

Diagnosis

Treatment

Prevention

Outcomes