Trypanosomiasis, African (T b gambiense)

Key Features

Essentials of Diagnosis

• Exposure to tsetse flies; chancre at bite site uncommon

• Hemolymphatic disease: Irregular fever, headache, joint pain, rash, edema, lymphadenopathy

• Meningoencephalitic disease: somnolence, severe headache, progressing to coma

• Trypanosomes in blood or lymph node aspirates; positive serologic tests

• Trypanosomes and increased white cells and protein in cerebrospinal fluid (CSF)

General Considerations

• African trypanosomiasis is caused by the hemoflagellates Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense

• T b gambiense causes West African trypanosomiasis and is transmitted in the moist sub-Saharan savannas and forests of west and central Africa

• Organisms are transmitted by bites of tsetse flies (Glossina species), which inhabit shaded areas along rivers

• Humans are the principal mammalian host, but domestic animals can be infected

• Trypanosomes ingested in a blood meal undergo a developmental period of 18–35 days in the fly

• When the fly feeds again on a new mammalian host, the infective stage is injected

Demographics

• The number of reported cases increased from the 1960s to1990s, and has since decreased greatly, although cases are reported from over 20 countries

• Total incidence has been estimated at about < 5000 cases per year, the large majority due to T b gambiense, with the largest number in the Democratic Republic of the Congo

• Infections are rare among travelers

Clinical Findings

Symptoms and Signs

• Chancres at the site of the bite are uncommon

• Patient may be asymptomatic for months before hemolymphatic disease develops

• Hemolymphatic disease progresses to meningoencephalitic disease, which leads to coma and death

Hemolymphatic disease

• Fever, headache, myalgias, arthralgias, weight loss, and lymphadenopathy

• Discrete, nontender, rubbery nodes, referred to as Winterbottom sign when in a posterior cervical distribution

• Mild splenomegaly

• Transient edema

• Pruritic erythematous rash

• Febrile episodes may be broken by afebrile periods of up to several weeks

Meningoencephalitic disease

• Somnolence, irritability, personality changes

• Severe headache

• Parkinsonian symptoms

Differential Diagnosis

• T b rhodesiense infection

• Malaria

• Influenza and pneumonia

• Tuberculosis

• Infectious mononucleosis

• Leukemia or lymphoma

• HIV

• Arbovirus encephalitis

• Wilson disease

• Psychosis due to other causes, eg, neurosyphilis

Diagnosis

Laboratory Tests

• During the hemolymphatic stage, detection of parasites in Giemsa-stained blood smears is difficult

• Serial specimens should be examined, since parasitemias vary greatly over time

• Meningoencephalitic (or second stage) disease is defined by the World Health Organization as CSF showing at least 5 mononuclear cells per mcL, elevated protein, or trypanosomes

• Concentration techniques can aid identification of parasites in blood or CSF

• Serologic tests are positive

• The simple card agglutination test for trypanosomes (CATT)

  • Has excellent sensitivity and specificity

  • Can be performed in the field

  • However, the diagnosis should be confirmed by identification of the parasites

• Field-applicable immunochromatographic lateral ...