Hemoflagellates

• Zoological classification of hemoflagellates

  • Phylum: Sarcomastigophora
  • Subphylum: Mastigophora
  • Class: Kinetoplastidea
  • Order: Trypanosomatida
  • Family: Trypanosomatidae
  • Genera: Leishmania and Trypanosoma

  
• Trypanosomes


  Have two hosts: Vertebrate hosts (definitive hosts) and Insect vectors (intermediate hosts)
• Digenetic parasites


  Trypanosoma cruzi is the etiologic agent of Chagas disease/American trypanosomiasis
• Trypanosoma cruzi


  • Intracellular parasite
  • Myocytes and reticuloendothelial cells are the most heavily infected cells
• Arthropod vector


  Reduviid bugs (Triatoma, Parastrongylus, Rhodnius)
• Zoonotic mammalian reservoir hosts for Trypanosoma cruzi

  • Domestic animals
  • Armadillos
  • Raccoons
  • Rodents
  • Marsupials
  • Some primates
• Stages of development of Trypanosoma cruzi

  • Amastigote – tissue cells
  • Promastigote
  • Epimastigote
  • Trypomastigote – bloodstream
• Insect vector


  • Amastigote, epimastigote, promastigote forms occur in the midgut
  • Infective metacyclic trypomastigote appear in the hindgut

  
• Amastigote


  • Round/ ovoid in shape
  • Usually found in small groups of cyst-like collections in tissue

  
• Trypomastigote


  • Short, stumpy to long, slender
  • Pointed posterior end
  • Narrow undulating membrane with 2-3 undulations
  • Single thread-like flagellum originating near the kinetoplast
  • Characteristically C-shaped in stained specimens, also been described as U- or S- shaped with prominent kinetoplast
• Pathogenesis and clinical manifestations of Chagas disease

  • Acute phase
  • Chronic phase
• Acute phase of Chagas disease


  • Focal or diffuse inflammation mainly affecting myocardium
  • Nonspecific signs and symptoms: fever, malaise, nausea, vomiting, generalized lymphadenopathy
  • Cutaneous manifestations
• Chagoma


  • Furuncle-like lesions associated with induration, central edema, and regional lymphadenopathy
  • Represent site of entry of parasite

  
• Romaña's sign


  • Eyelid swelling
  • Unilateral painless bipalpebral edema and conjunctivitis
  • May involve lacrimal gland and surrounding LNs
• Chronic phase of Chagas disease

  • Fibrotic reaction → injury to myocardium, cardiac conduction network, enteric nervous system
• Chronic phase effects on the heart

  • Cardiomegaly
  • Congestive heart failure
  • Thromboembolism
  • Arrythmias
• Diagnosis - primary tool


  Complete patient history
• Information needed for patient history

  • Possible exposure
  • Place or residence or work
  • Recent blood transfusion in an endemic area
  • Contact or exposure to intermediate host
• Definitive diagnosis (acute phase)


  • Direct visualization of parasites in thick and thin blood smears using Giemsa stain
  • CSF, tissue samples, or lymph can also be used for parasite visualization
  • Only in first two months of acute disease, trypomastigotes can be seen in direct examination
• Other diagnostic techniques


  • Concentration methods (microhematocrit)
  • Blood culture
  • PCR
• Xenodiagnosis


  Laboratory-reared triatomine bugs allowed to feed on suspected patients, later examined for presence of metacyclic trypomastigotes
• Diagnostic techniques for chronic phase

  • Enzyme-linked immunosorbent assay (ELISA)
  • Indirect hemagglutination
  • Indirect immunofluorescence
  • PCR
• WHO recommends using at least two techniques with concurrent positive results before a diagnosis of Chagas disease is made
• Trypanosoma brucei gambiense


  • Primarily affects humans
  • Reservoir hosts: dogs, pigs, sheep
  • Responsible for chronic type of sleeping sickness
• Trypanosoma brucei rhodesiense


  • Primarily zoonosis of cattle and wild animals
  • Man as accidental hosts
  • Acute and rapidly fatal form of sleeping sickness
• Trypomastigote forms of Trypanosoma brucei

  • Polymorphic (typical slender forms to short, stumpy forms)
  • Flattened and fusiform in shape
  • Body tapers anteriorly and blunt posteriorly
  • Centrally located nucleus with large central karyosome
  • Undulating membrane
  • Single flagellum that runs along edge of undulating membrane and becomes free anteriorly

  
• Trypanosoma brucei gambiense sleeping sickness

  • Manifests MONTHS/YEARS after INITIAL INFECTION
• Trypanosoma brucei rhodesiense sleeping sickness

  • May appear just WEEKS after INFECTION
• Initial lesion in sleeping sickness

  • Local, painful, pruritic, erythematous chancre located at the bite site, progressing into a central eschar; resolving after 2 to 3 weeks
  • More common in Gambian sleeping sickness
• Early (hemolymphatic) stage of sleeping sickness


  • Parasites proliferate in bloodstream and lymphatics
  • Irregular bouts of fever, headache, joint and muscle pain, malaise
  • Anemia, myocardial inflammation, disseminated intravascular coagulation, renal insufficiency may occur
• Winterbottom's sign


  • Enlarged, non-tender, rubbery in consistency posterior cervical lymph nodes
  • In Gambian trypanosomiasis
• Late (meningoencephalitic) stage of sleeping sickness

  • Involvement of the CNS (brain, meninges)
  • Occurs 3 to 10 months after initial infection in Gambian infections but can manifest just a few weeks in Rhodesian trypanosomiasis
• Symptoms of late stage sleeping sickness

  • Apathy, behavioral changes, headache, sleep pattern changes
  • Convulsions, tremors, speech defects, speech and reflexes disturbances, paralysis
  • Kerandel's sign: deep, delayed hyperesthesia
• Antigenic variation


  • Ability of the trypomastigote to continuously change its surface coat, composed of variant surface glycoproteins
  • Host antibodies cannot recognize the parasite in subsequent recurrent waves of parasitemia
• Diagnosis - demonstration of trypomastigotes


  • In expressed fluid from a chancre, lymph node aspirate, CSF
  • Thick and Thin blood films can be stained with Giemsa
  • Buffy coat concentration method: recommended to detect parasites when they occur in low numbers

  
• Examination of trypomastigotes is usually done during the hemolymphatic stage, and is more useful for diagnosis of T. brucei rhodesiense due to relative higher levels of parasitemia
• Other diagnostic techniques for sleeping sickness

  • Enzyme-linked immunosorbent assay
  • Immunofluorescence
  • Indirect hemagglutination test
  • Mini-anion exchange centrifugation technique
  • PCR
• CSF examination in sleeping sickness

  • Increase in cell count
  • Increase in opening pressure
  • Increase in Protein concentration
  • Increase in IgM
• Old World Leishmania species

  • Leishmania tropica (Asia and Eastern Europe)
  • Leishmania aethiopica (Africa)
  • Leishmania major
• New World Leishmania species


  • Leishmania mexicana
  • Leishmania amazonensis
  • Leishmania guyanensis
  • Leishmania braziliensis
  • Leishmania chagasi