Typhus

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Typhus is a group of infectious diseases caused by Rickettsia bacteria, transmitted by lice, fleas, mites, and ticks. It includes epidemic typhus, endemic typhus, and scrub typhus, each caused by different species of Rickettsia.

Aetiology

Typhus is caused by infection with Rickettsia bacteria:

• Epidemic typhus: Caused by Rickettsia prowazekii, transmitted by body lice.
• Endemic (murine) typhus: Caused by Rickettsia typhi, transmitted by fleas.
• Scrub typhus: Caused by Orientia tsutsugamushi, transmitted by chigger mites.

Pathophysiology

The pathophysiology of typhus involves:

• The bacteria enter the body through the bite of an infected vector (lice, fleas, mites, or ticks).
• The bacteria then invade the endothelial cells lining the small blood vessels, causing vasculitis.
• This results in widespread inflammation, thrombosis, and leakage of fluid into surrounding tissues, leading to the characteristic rash and other systemic symptoms.

Risk Factors

• Living or travelling in areas with poor sanitation and overcrowding.
• Exposure to vectors such as lice, fleas, mites, or ticks.
• Occupations involving close contact with animals or outdoor activities (e.g., farming, military personnel).
• Immunosuppression.

Signs and Symptoms

The signs and symptoms of typhus vary by type, but commonly include:

• High fever
• Severe headache
• Rash (typically starting on the trunk and spreading to the limbs)
• Muscle pain
• Chills
• Confusion
• Nausea and vomiting
• In severe cases, complications such as pneumonia, myocarditis, or meningoencephalitis

Investigations

Specific investigations to diagnose typhus include:

• Serology: Detection of specific antibodies against Rickettsia species using immunofluorescence assay (IFA) or enzyme-linked immunosorbent assay (ELISA).
• Polymerase Chain Reaction (PCR): Detection of Rickettsia DNA in blood or tissue samples.
• Culture: Isolation of Rickettsia bacteria from blood or tissue samples (rarely performed due to difficulty and risk).

Management

Primary Care Management

• Antibiotics: Doxycycline is the antibiotic of choice for all forms of typhus or azithromycin (for those unable to take doxycycline).
• Supportive care: Ensuring adequate hydration, rest, and management of symptoms such as fever and pain.
• Prevention: Advising on measures to avoid vector exposure, such as using insect repellent, wearing protective clothing, and maintaining good hygiene and sanitation.

Specialist Management

• Hospitalisation: For severe cases or patients with significant comorbidities. This may include intravenous antibiotics, oxygen therapy, and intensive care support.
• Management of complications: Treating severe manifestations such as pneumonia, myocarditis, or meningoencephalitis.
• Public health measures: Reporting cases to public health authorities and investigating potential sources of infection to prevent outbreaks.

References

1. NHS (2024) Typhus. Available at: https://www.nhs.uk/conditions/typhus/ (Accessed: 24 June 2024).
2. Centers for Disease Control and Prevention (2024) Typhus Fevers. Available at: https://www.cdc.gov/typhus/index.html (Accessed: 24 June 2024).
3. World Health Organization (2024) Typhus. Available at: https://www.who.int/health-topics/typhus (Accessed: 24 June 2024).
4. British Medical Journal (2024) Typhus: clinical features, diagnosis, and management. Available at: https://www.bmj.com/content/350/bmj.h2487 (Accessed: 24 June 2024).

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