Parasitology: Hemoflagellates & Trypanosomes

Answer 1

American trypanosomiasis: T. cruzi

• Epidemiology: Latin Americas & Trinidad; women & children more at risk (go to sleep first)
• Vector: Kissing bugs: feed on mouth and eyes; Hemimetabolous: no pupal stage b/w larva & adu
• Features: Typicall C-shaped (see fig)
  
  • Trypomastigote stage: characteristic of the genus Trypanosoma in the mammalian host bloodstream as well as infective metacyclic stages in the fly vector;
  • Amastigote stage: inside cells of host
• Sx: Chagoma (Romana’s sign): unilocular conjunctivitis, lasts for several months;
  Fever, progressive anemia, edema, lymphadenopathy, hepatosplenomegaly, EKG abnormalities, CNS involvement -> death or recovery
• Pathology: edema, degeneration of parasitized tissue, destruction of mycoardial fibers and ganglion cells (cardiomegaly, apical aneurysms), destruction of myenteric plexus (megacolon)
• Dx: C-shaped on thin film, xenodiagnosis (let kissing bugs feed on Pt purposely and sample fecal pellet of bug; +ve test typically show 10e4 of parasites), serology Ag, DNA probes, PCR than DNA
• Rx: Benzidazole & Nifurtimox; effective against trypomastigote stage not amastigotes; screening is important as rx only effective in acute phase
• Control: ITN, screening, education, improved housing, no vaccine available

Question 2

T. rangeli

Answer 2

• Epidemiology: Apathogenic trypanosome found in same geographical area as T. cruzi
• Features: Prominient undulating membrane long pointed posterior end
• Vector:
• Dx testing:

Answer 3

African trypanosomiasis: sleeping sickness

T. brucii gambience

T. brucii rhodesiense

• • Epidemiology
• Vector: Tsetse flies, holometabolous, zoonotic
• Features:
  
  • T. brucii gambiense
• only on stage of parasites (no amastigote stage)
• East Africa: acute disease
• West Africa: chronic disease
• Sx: Enlarged cervical lymph nodes (Winterbottoms sign), sleepiness, T.b. rhodesiense is acute, gambiense is chronic
• Dx: hx & clinical signs, demonstration of trypomastigotes on buffy coat/blood film, PCR/DNA (direct), ELISA (indirect)
• Rx: Suraman or Eflornithine (IV), removes tryps except in CNS; Melarsoprol (crosses BBB)
• Control: Biconical trap (plastic bag traps where Tze fly gets cooked in the bags during the day)

Answer 4

Leishmania

• • Epidemiology: both old & new world
• Vector: sandfly spp Lutzomyia spp (New world); Phlebotomus (Old World)
• Features: Amastigotes in WBC (vertebrate host); Promastigote (vector in new host); after 48h amastigotes (binary fission) pack macrophage and are released when cell bursts
  
  • cutaneous Leishmaniasis
  • visceral Leishmaniasis
• Dx: spleen or bone marrow aspirate showing amastigotes is gold standard; rK39 Dipstick test used in field (detects antigen, commercially available test kits)

visceral Leishmaniasis

• L. donovani complex (Kala-azar)
• 4-6 d move to inner organs,
• Sx: early & late
  
  • early: irregular fever, anaemia, leucopenia, diarrhoea, bleeding gums, joint pain, wt loss
  • late: enlargement of lymph nodes, splenomegaly, hepatomegaly, death
• Rx: Amphoteracin B, pentavalent antimonial compounds (sodium stibogluconate - Pentostam), paramomycin, miltefosine
• Epidemiology: Africa & NE India

Cutaneous Leishmaniasis

• Sx: small red papule, wet ulcer (Leishmania major
  ) or dry ulcer (Leishmania tropica aka Oriental sore -> heal spontaneously)
• Dx: travel Hx, clinical signs, amastigotes in aspirated fluid from ulcer (direct)
• Rx: same as L. donovani

New World Mucocutaneous

• Leishmania braziliensis complex
• Sx: small cutaneous papule, ulcer, oral and/or nasal lesions may develop after 3-20 yrs (very destructive)
• Dx: amastigotes in lesions (direct), culture/lab animals (monoclona Ab)
• Rx: same as L. donovani
• Epidemiology: males more infected than females (occupational disease), rain forest transmission zoonoses (sloths, rodents, dogs are reservoir hosts)
• Control: flea collar on dogs