MEDICAL PARASITOLOGY

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MEDICAL PARASITOLOGY ENTOMOLOGY

• LECTURER
• SR. NORAZSIDA RAMLI

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BLOOD TISSUE FLAGELLATES/HAEMOFLAGELLATES
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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.

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• Kingdom Protisata
• Phylum Sarcomastigophora
• Class Zoomastrgophora
• Order Kimetplastida
• Family Trypanosomatidae
• Genus Trypanosoma
• Species brucei, cruzi, rangeli

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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.

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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.

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T. burgei gambiense
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Tsetse fly
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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.

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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.

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Life cycle of T.brucei
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Transmission

• Occurs through
• the bite of an infected tsetse fly,
• blood transfusion,
• Organ transplant, and
• congenital transmission (from pregnant mother to
  fetus).

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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.

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• 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 Winterbottoms sign.

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• Symptoms of glandular stage
• -erythematous (red) rash
• -pruritus (severe itching)
• -localized joint edema (swelling)
• -delayed sensation of pain (Kerandels sign).

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• 3)Meningoencephalitic stage
• -CNS involvement
• -6 months to a year after the onset of 1st
  symptoms.
• -the patients health deteriorates with increased
  fatigue
• -mental dullness
• -apathy
• -diminished motor control
• -somnolence (excessive sleepiness)
• -emaciation
• -trypomastigotes may be seen in the patients
  spinal fluid
• -sleepiness progresses to coma and eventual death

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Diagnosis

• Microscopic examination
• Concentration technique centrifugation
• Serologic technique Card Agglutination
  Trypanosomiasis Test (CATT)

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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.

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• 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.

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• 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

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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

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T. burgei rhodesiensi
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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.

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Life cycle

• Similar to T.b. gambiense

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Transmission

• Transmitted by the bite of an infected tsetse
  fly
• -G. pallidipes
• -G. morsitans
• -G. swynnertoni

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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

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Laboratory diagnosis

• Similar to T.b.gambiense

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Treatment

• Similar to T.b.gambiense
• No vaccine available

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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.

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T. cruzi
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Geographical distribution
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Life cycle of T. cruzi
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Trypanosoma cruzi vector

• Triatomine bug,, defecating on the wound after
  taking a blood meal

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Reduviid bug - triatoma species
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Ideal habitat for reduviid bugs
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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

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Treatment

• Nifurtimox
• Allupurinol
• Benznidazole
• Diuretic treatment
• Surgical intervention