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Learn about the morphology, life cycle, diagnosis, treatment, and prevention of hemoflagellates such as Trypanosoma brucei and Trypanosoma cruzi. Understand the causes, symptoms, and transmission of African sleeping sickness and Chagas disease. Discover the role of tsetse flies as vectors in these parasitic infections.
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MEDICAL PARASITOLOGY &ENTOMOLOGY LECTURER: SR. NORAZSIDA RAMLI
Morphologic forms • There are 4 morphologic forms seen in hemoflagellates: • Amastigote • Promastigote • Epimastigote • Trypomastigote -they can exist in two or more of the 4 morphologic forms depending on the species.
Kingdom: Protisata • Phylum: Sarcomastigophora • Class: Zoomastrgophora • Order: Kimetplastida • Family: Trypanosomatidae • Genus:Trypanosoma • Species:brucei, cruzi, rangeli
Trypanosoma sp. • T. brucei gambiense - cause: West African sleeping sickness • T. brucei rhodesiense - cause: East African sleeping sickness • T. cruzi - cause: American trypanosomiasis or ‘Chagas’ disease. • T. rangeli - Cause: T. rangeli infection.
T. b. gambiense • Cause West African sleeping sickness. • “tsetse fly belt” is a large area of Africa that has reported cases of African sleeping sickness. • Vector/ intermediate host: Glossina (tsetse) fly.
West African sleeping sickness • Also known as Gambian trypanosomiasis. • Can be found in the wet lowlands and rainforest of west and central Africa where the tsetse breed in the moist areas around riverbanks. • Chronic course- ends with central nervous involvement and death after several years of durations.
Geographical distribution • The savanna vectors G.morsitans and G. palidipes are responsible for the transmission of T. rhodesiense in East Africa, while the principal vectors of west African sleeping sickness are G. palpalis, G. fuscipes and G. tachinoides.
Transmission • Occurs through: • the bite of an infected tsetse fly, • blood transfusion, • Organ transplant, and • congenital transmission (from pregnant mother to fetus).
Pathogenesis • Infection is characterized by 3 progressive stages: 1) An asymtomatic incubation period -right after infection -a few days to several weeks. -non African shorter than African natives. -parasite multiply locally. -local inflammation leads to the development of a painful ulcerative lesion called: trypanosomal chancre at the bite site.
2) Hematogenous spread of the parasites and the involvement of the lymphatic system. • Trypomastigotes may be seen in the blood film examination. • Symptoms: febrile (fever) followed by afebrile periods, headache, malaise, weakness, anorexia, and night sweats. • Glandular enlargement and lymphadenopathy (enlargement of the lymph nodes). • Enlargement of the postcervical chain of lymph nodes, which is known as ‘Winterbottom’s sign’.
Symptoms of glandular stage: -erythematous (red) rash -pruritus (severe itching) -localized joint edema (swelling) -delayed sensation of pain (Kerandel’s sign).
3)Meningoencephalitic stage -CNS involvement -6 months to a year after the onset of 1st symptoms. -the patient’s health deteriorates with increased fatigue -mental dullness -apathy -diminished motor control -somnolence (excessive sleepiness) -emaciation -trypomastigotes may be seen in the patient’s spinal fluid -sleepiness progresses to coma and eventual death
Diagnosis • Microscopic examination • Concentration technique – centrifugation • Serologic technique – Card Agglutination Trypanosomiasis Test (CATT)
Treatment • Pentamidine isothionate -used to cure Gambian trypanosomiasis in the hemolymphatic stage of infection. -administered by intramuscular injection. -effective only in the early stage of disease bcoz of its inability to cross the ‘blood-brain barrier’.
Suramin • Effective only in the early stage of disease b4 CNS involvement • Administered intravenously • Has more toxic side effects than pentamidine. • May be prescribed during pregnancy.
Melarsoprol • A triavalent arsenic compound. • Much more toxic than pentamidine or suramin. • Effective for later stages • Administered intravenously • Can effectively penetrate the blood brain barrier
Prevention • Control, management & avoidance of the insect vector • Clearing of vegetation where tsetse flies breed • Wide use of insecticides • Travelers to endemic areas encouraged to wear long sleeved protective clothing • Wear thick Khaki or olive drab clothing coz tsetse flies are attracted to bright and dark colors. • Use bed net • Insect repellent
T. brucei rhodesiense • Course of East African sleeping sickness • 1st isolated from a patient in Rhodesia • Clinical presentation- more fulminant course and severe symptoms • The incidence is far less than Gambian disease but if left untreated – death will ensure within several weeks to months rather than years.
Life cycle • Similar to T.b. gambiense
Transmission • Transmitted by the bite of an infected tsetse fly: -G. pallidipes -G. morsitans -G. swynnertoni
Pathogenesis • Produce a more acute form • Stages of disease and symptomology similar with Gambian infection. • Disease progress rapidly • Much shorter clinical course • Incubation period: shortened by the abrupt onset of febrile episodes
Laboratory diagnosis • Similar to T.b.gambiense
Treatment • Similar to T.b.gambiense • No vaccine available
T. cruzi • Cause of American trypanosomiasis/ chagas disease. • Chagas disease: named for the Brazilian medical student, Carlos Chagas – who has discovered the parasite in 1909. • Has an intracellular amastigote stage that develops in cardiac, brain and visceral tissues. • Also has trypomastigotes in the peripheral circulation.
Trypanosoma cruzi vector • Triatomine bug,, defecating on the wound after taking a blood meal
Transmission • Transmitted by : reduviid bug -also known as kissing bug or triatomid bug. -vector: genus Panstrongylus or Triatoma • Transmitted via: -the bite of infected vector -blood transfusion -transplacental route -accidental ingestion of an infected insect
Treatment • Nifurtimox • Allupurinol • Benznidazole • Diuretic treatment • Surgical intervention
