Introduction

African trypanosomiasis, also known as sleeping sickness, is an insect-borne parasitic disease of humans and other animals caused by protozoa Trypanosoma brucei usually transmitted by the bite of an infected tsetse fly, most common in rural areas.

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History

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Epidemiology

Transmission

• Vector transmission (M/C)
• Other forms:
  • Mother-to-child infection
  • Laboratories: accidental infections
  • Blood transfusion
  • Sexual contact

Life cycle:

• Two types that infect humans:
  • Trypanosoma brucei gambiense (TbG) (98% cases)
  • Trypanosoma brucei rhodesiense (TbR)

Vector:

• Tsetse fly (painful bite)

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Clinical features

First stage “hemolymphatic phase”

• Fever, headaches, joint pains, and itching
  • Fever is intermittent, with attacks lasting from a day to a week, separated by intervals of a few days to a month or longer
• Invasion of the circulatory and lymphatic systems by the parasites:
  • Lymphadenopathy
  • Winterbottom’s sign (Tell-tale swollen lymph nodes along the back of the neck)
• Chancre (red sore) develops at the location of the tsetse fly bite
• If untreated, the disease overcomes the host’s defenses and can cause more extensive damage:
  • Anaemia, endocrine, cardiac, and kidney dysfunctions

Second phase “neurological phase”

Begins when the parasite invades the central nervous system by passing through the blood-brain barrier (BBB)

Damage caused in the neurological phase is irreversible

• Disruption of the sleep cycle (leading symptom, leading to the name ‘sleeping sickness‘)
  • Disorganized and fragmented 24-hour rhythm of the sleep-wake cycle (eg. daytime sleep episodes and nighttime periods of wakefulness)
• Other neurological symptoms:
  • Confusion, tremor, general muscle weakness, hemiparesis, and paralysis of a limb
  • Parkinson-like movements
    • Due to non-specific movement disorders and speech disorders
• Psychiatric symptoms (can sometimes dominate the clinical diagnosis):
  • Irritability, psychotic reactions, aggressive behaviour, or apathy

Untreated infections:

• Progressive mental deterioration leading to coma
• Systemic organ failure and death (within months)

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Diagnosis

Investigations

Detection of trypanosomes:

• Samples for study:
  • Chancre fluid, lymph node aspirates, blood, bone marrow, and CSF (during neurological stage)
• Preparation of samples:
  • Wet preparation (can be used to look for the motile trypanosomes)
  • Fixed (dried) smear (stained using Giemsa’s or Field’s technique and examined under a microscope)
• Concentration of samples (prior to microscopic examination):
  • Blood samples:
    • Centrifugation followed by examination of the buffy coat
    • Mini anion-exchange/centrifugation
    • Quantitative buffy coat (QBC) technique
  • Other samples:
    • Centrifugation followed by examination of the sediment

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Serological tests:

• Dried blood:
  • Micro-CATT
• Whole blood samples:
  • wb-CATT
  • wb-LATEX

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Management

First stage

• T. b. gambiense: IV/IM pentamidine
• T. b. rhodesiense: IV suramin

Second stage

• T. b. gambiense:
  • First-line treatment regimens:
    • Nifurtimox + eflornithine, or
    • Nifurtimox-eflornithine combination treatment (NECT), or
    • Eflornithine (alone)
• IV melarsoprol
  • T. b. rhodesiense (1st-line)
  • T. b. gambiense (2nd-line)