Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense
Scientific classification
Class: Kinetoplastea
Order: Trypanosomatida
Phylum: Euglenozoa
Family: Trypanosomatidae
Domain: Eukaryota
Genus: Trypanosoma
History
Trypanosome was first isolated from the blood of a steamboat captain on the Gambia river in 1901 (hence the name gambiense) by Forde
Dutton, in 1902, proposed the name Trypanosoma gambiense.
Stephens and Fantham discovered T brucei rhodesiense in 1910 from the blood of a patient in Rhodesia suffering from sleeping sickness.
Treatment
Suramin
melarsoprol
Pentamidine
Distribution
It is found in Eastern and Central Africa (Uganda, Tanzania, Zambia and Mozambique)
Trypanosomiasis is believed to have been existing in tropical Africa from antiquity
Habitat
Trypanosomes live in man and other vertebrate host. They are essentially a parasite of connective tissue, where they multiply rapidly and then invade regional lymph nodes, blood and finally may involve central nervous system.
It is endemic in scattered foci in West and Central Africa between 15° land 18°S latitudes.
Morphology
Vertebrate forms
Insect forms
Exists as trypomastigote form, which is highly pleomorphic.
It occurs as a long slender form, a stumpy short broad form with attenuated or absent flagellum and an intermediate form.
The trypomastigotes are about 15-40 μm long and 1.5- 3.5 μm broad.
trypomastigotes are seen as colorless, spindle-shaped bodies that move rapidly, spinning around the red blood cells.
In smears stained with Giemsa or other Romanowsky' stain, the cytoplasm appears pale blue and the nucleus appears red
Epimastigotes
Metacyclic trypomastigote forms
Life Cycle
T. brucei gambiense passes its life cycle in two hosts: Vertebrate host: Man, game animals and other domestic animals. Invertebrate host: Tsetse fly.
Infective form: Metacyclic trypomastigote forms are infective
Metacyclic stage of Trypomastigotes are inoculated into a man through skin when an infected tsetse fl y takes a blood meal.The parasite transforms into slender forms that multiply asexually for 1-2 days before entering peripheral blood and lymphatic circulation.
These become "stumpy" via intermediate forms and enter the bloods stream
Trypomastigotes are ingested by tsetse fly during blood meal.
In the midgut of the fly, short stumpy trypomastigotes develop into long, slender forms and multiply.
After 2- 3 weeks, they migrate to the salivary glands, where they develop into epimastigotes, which multiply and fill the cavity of the gland and eventually transform into the infective metacyclic trypomastigotes.
Development of the infective stage within the tsetse fly requires 25-50 days
Pathogenicity and Clinical Features
There is an initial period of parasitemia
A painless chancre (trypanosomal chancre) appears on skin at the site of bite by tsetse fly, followed by intermittent fever, chills, rash, anemia, weight loss and headache.
Systemic trypanosomiasis without central nervous system involvement is referred to as stage 1 disease.
There is hepatosplenomegaly and lymphadenopathy,
particularly in the posterior cervical region (Winterbottom's sign).
Hematological manifestations seen in stage I. With the invasion of central nervous system, which occurs after several months, the "sleeping sickness" starts.
Histopathology shows chronic meningoencephalitis. meninges are heavily infiltrated with lymphocytes, plasma cells and morula cells, which are atypical plasma cells containing mulberry-shaped masses of lgA.
Abnormalities in cerebrospinal fluid (CSF) include raised intracranial pressure, pleocytosis and raised total protein concentrations.
Febrile paroxysms arc more frequent and severe. Edema, myocarditis and weakness are more prominent in East African sickness.
Laboratory Diagnosis
Wet mount preparation of lymph node aspirates
Culture In Weinman's or Tobie's medium.
CT scan Shows cerebral edema
Antibody detection IHA, IIF, ELISA, CATT, CFT
Molecular diagnosis PCR
Blood incubation infectivity test: For differentiation between the "human strains" and "animal strains" of T. brucei, the blood incubation infectivity test {BIIT} had been widely used.
