Trypanosomiasis, African (T b rhodesiense)

Essentials of Diagnosis

• Exposure to tsetse flies

• 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

General Considerations

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

• The organisms are transmitted by bites of tsetse flies (genus Glossina), which inhabit shaded areas along streams and rivers

• 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

• T b rhodesiense causes East African trypanosomiasis, and is transmitted in the savannas of east and southeast Africa

• T b rhodesiense infection is primarily a zoonosis of game animals and cattle; humans are infected sporadically

Demographics

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

• Infections are rare among travelers, including visitors to game parks

• Chancres at the bite site; lesion is painful and measures 3–10 cm

• Symptom onset usually occurs within a few days of the insect bite

• The hemolymphatic stage includes intermittent fever and rash, but lymphadenopathy is less common than with West African disease

• Myocarditis can cause tachycardia and death due to arrhythmias or heart failure

• Microscopic examination of fluid expressed from a chancre or lymph node may show motile trypanosomes or, in fixed specimens, parasites stained with Giemsa

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

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

• Meningoencephalitic (or second stage) disease is defined by the World Health Organization as cerebrospinal fluid (CSF) showing at least five mononuclear cells per microliter, elevated protein, or presence of trypanosomes

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

• Serologic tests are also available

• Field-applicable immunochromatographic lateral flow rapid diagnostic tests that cost less than CATT and are simpler to perform are available

• Combining tests improves sensitivity and specificity

• Molecular diagnostic tests, including PCR and field-friendly loop-mediated isothermal amplification (LAMP) are available, but these are not yet standardized or routinely available

• Pentamidine and eflornithine are not reliably effective

• Suramin

  • Used to treat early disease

  • Dosing regimens vary: 100–200 mg test dose, then 20 mg/kg (maximum 1 g) intravenously on days 1, 3, 7, 14, and 21 or weekly for five doses

  • Toxicities include vomiting and, rarely, seizures and shock during infusions as well as subsequent fever, rash, headache, neuropathy, and kidney and bone marrow dysfunction

• Melarsoprol

  • Used for CNS infection since suramin does not enter CNS

  • Dosage: three series of 3.6 mg/kg/day intravenously for 3 days, with 7-day breaks between the series or a 10-day intravenous course with 0.6 mg/kg on day 1, 1.2 mg/kg on day 2, and 1.8 mg/kg on days 3–10)

  • Immediate side effects include fever and gastrointestinal symptoms

  • Most important side effect is a reactive encephalopathy

    • Can progress to seizures, coma, and death

    • To help avoid this side effect, corticosteroids are coadministered (dexamethasone 1 mg/kg/day intravenously for 2–3 days or oral prednisolone 1 mg/kg/day for 5 days, and then 0.5 mg/kg/day until treatment completion)

  • In addition, increasing resistance to melarsoprol is a serious concern

Prognosis

• If untreated, progresses over weeks to months to meningoencephalitic disease, somnolence, coma, and death

Prevention

• Individual prevention should include

  • Wearing neutral-colored clothes with long sleeves and pants

  • Insect repellents

  • Using mosquito nets while sleeping

• Control programs focusing on vector elimination and treatment of infected persons and animals have shown good success but suffer from limited resources