Occupational Tuberculosis

Occupational tuberculosis is tuberculosis infection or disease acquired through work. Healthcare workers, laboratory staff, prison and shelter staff, miners and workers in other high risk settings are most affected.

Epidemiology. Risk is several fold higher than in the general population in high burden regions and in untreated or undiagnosed patient contact. Silica exposure and HIV raise risk further.

Infection and disease. Infection with Mycobacterium tuberculosis is usually latent. About 5 to 10% of infected immunocompetent people develop active disease, most within 2 years.

Exposure risk. Risk rises with duration and intensity of contact with an infectious pulmonary case, poor ventilation and delay in isolation. Aerosol generating procedures and mycobacteriology laboratory work are high risk.

Outbreaks. Workplace clusters occur and need contact investigation.

Pathophysiology.

Inhaled droplet nuclei reach the alveoli, where macrophages ingest the bacilli. Cell mediated immunity forms granulomas that contain infection in most people.

Failure of containment, from immunosuppression, HIV, silica or ageing of the granuloma, leads to active disease.

• Pulmonary: cough over 2 weeks, sputum, haemoptysis, fever, night sweats, weight loss and fatigue.
• Extrapulmonary: lymph node, pleural, bone, meningeal or abdominal disease, more frequent with HIV.
• Latent infection has no symptoms.

Red flags.

• Haemoptysis, respiratory failure or rapid weight loss.
• Headache with neck stiffness or confusion (meningitis).
• Sputum positive disease in a worker who cares for vulnerable patients.

• Occupational exposure history and contact investigation of a known source case.
• Chest radiograph; CT for atypical disease.
• Sputum smear, culture and molecular testing with rifampicin resistance detection, with at least 2 samples; bronchoscopy for non-productive patients. Drug susceptibility testing on all positive cultures.
• HIV test; baseline liver function, renal function and visual acuity.
• Latent infection in exposed workers: interferon gamma release assay preferred, or tuberculin skin test (induration of 10 mm or more, or 5 mm or more with HIV or immunosuppression), after excluding active disease. Baseline testing at employment, and after exposure at about 8 to 10 weeks.

Differential diagnosis. Non-tuberculous mycobacterial disease, bacterial pneumonia, fungal infection, sarcoidosis, lung cancer, silicosis, lung abscess.

Drug susceptible disease, adult doses:

• Isoniazid 5 mg/kg orally once daily, maximum 300 mg, for 6 months, with pyridoxine 10 mg once daily (25 to 50 mg in high risk patients). Monitor liver enzymes and peripheral neuropathy. No renal adjustment; caution in liver disease.
• Rifampicin 10 mg/kg orally once daily, maximum 600 mg, for 6 months, taken fasting. Monitor liver enzymes and interactions (warfarin, direct oral anticoagulants, hormonal contraception, antiretrovirals, corticosteroids). No renal adjustment; avoid in severe liver disease.
• Pyrazinamide 25 mg/kg orally once daily, maximum 2 g, for the first 2 months. Monitor liver enzymes and uric acid. If eGFR is under 30, give 25 mg/kg three times weekly; avoid in severe liver disease.
• Ethambutol 15 mg/kg orally once daily, maximum 1.6 g, for the first 2 months. Monitor visual acuity and colour vision monthly. If eGFR is under 30, give 15 to 25 mg/kg three times weekly.
• Stop hepatotoxic drugs for ALT over 3 times the upper limit with symptoms, or over 5 times without symptoms, and reintroduce under specialist direction. Drug resistant disease needs a specialist designed regimen.
• HIV co-infection: start antiretroviral therapy within 2 weeks if CD4 is under 50 cells/mm3, otherwise within 8 weeks; add co-trimoxazole prophylaxis; adjust for interactions.
• Latent infection, active disease excluded: rifampicin 10 mg/kg orally once daily (maximum 600 mg) for 4 months, with regular monitoring and interaction checks. Alternative: isoniazid 5 mg/kg orally once daily (maximum 300 mg) with pyridoxine for 6 months, monitoring liver enzymes and neuropathy.
• Infection control: place the patient in a single negative pressure room and use fit tested FFP2 or N95 respirators for staff. End isolation after at least 2 weeks of effective therapy with clinical improvement and sputum conversion, and later in drug resistant disease.
• Workers with infectious disease stay off work until non-infectious by sputum and clinical review.
• Contact tracing of co-workers, patients and household members, with testing and preventive treatment as needed.

Monitoring. Symptoms and weight monthly; sputum culture at 2 months and at end of treatment; liver tests at 2 and 4 weeks then as indicated; visual checks monthly on ethambutol; directly observed therapy where feasible.

Referral and escalation. Notify as required; tuberculosis or respiratory specialist; occupational physician for return to work, workplace investigation and compensation where required.