mod 5

• Hemoflagellates are flagellated protozoa found in peripheral blood circulation
• Hemoflagellates complete their life cycle in two hosts: vertebrate host and insect vector
• Hemoflagellates belong to:

  • Phylum: Euglenozoa
  • Class: Kinetoplastea
  • Order: Trypanosomatida
  • Family: Trypanosomatidae
  • Genera: Leishmania and Trypanosoma
• Morphology of hemoflagellates:

  • Oval to elongated body, nucleus, and a single flagellum arising from kinetoplast
  • Kinetoplast consists of blepharoplast and parabasal body connected by a delicate fibril
  • Axoneme (or axostyle) extends from blepharoplast to the cell wall
  • Exist in four morphological stages: amastigote, promastigote, epimastigote, and trypomastigote
• Trypanosomes are hemoflagellates residing in peripheral blood and tissues of their host
• Human Trypanosomes:

  • Trypanosoma cruzi: Causative agent of South American trypanosomiasis (Chagas’ disease)
  • Trypanosoma brucei: Causes African trypanosomiasis with subspecies Trypanosma brucei rhodesiense and Trypanosma brucei gambiense
  • Trypanosoma rangeli: Nonpathogenic species
• Animal Trypanosomes:

  • Trypanosoma brucei brucei: Causes "nagana" in cattle
  • T. congolense and T.vivax cause diseases similar to T. brucei brucei
  • Trypanosma evansi: Causes "Surra" in horses and other animals
  • Trypanosma lewisi: Causes a harmless infection in rodents
  • Trypanosma equiperdum: Causes "Stallion’s disease" in horses
• Trypanosoma brucei complex consists of three subspecies: T. brucei gambiense, T. brucei rhodesiense, and T. brucei brucei
• Trypanosoma brucei gambiense:

  • Endemic in scattered foci in West and Central Africa
  • Principal vectors are Glossina palpalis and Glossina tachynoides
  • Morphology includes trypomastigote form in vertebrate host and epimastigotes and metacyclic trypomastigotes in the tsetse fly vector
• Trypanosoma brucei gambiense completes its life cycle in two hosts: humans and tsetse flies
• Pathogenesis and Clinical Features of Trypanosoma brucei gambiense:

  • Causes African trypanosomiasis (West African sleeping sickness)
  • Chronic illness with initial parasitemia, lymph node localization, chancre, fever, anemia, weight loss
  • Invasion of CNS marked by headache, mental dullness, apathy, and sleepiness
  • Histopathology shows chronic meningoencephalitis with cellular infiltration and neuronal degeneration
• Trypanosoma brucei rhodesiense:

  • Found in Eastern and Central Africa
  • Principal vectors are Glossina morsitans, G. palpalis, and G. swynnertoni
  • Causes East African sleeping sickness with acute illness and lymphadenitis
• Diagnosis of Human African Trypanosomiasis:

  • Microscopic examination of lymph node aspirates, CSF, and chancre fluid
  • Culture, animal inoculation, serodiagnosis, and molecular diagnosis are also used
• Serodiagnosis can detect specific antibodies or antigens in serum and CSF
• Molecular diagnosis involves PCR on clinical specimens
• Suramin is the drug of choice for rhodesiense HAT
• Pentamidine is the drug of choice for gambiense human African trypanosomiasis (HAT) before CNS involvement
• Melarsoprol is the drug of choice for HAT with CNS involvement
• Prevention and control methods for African trypanosomiasis include early diagnosis and treatment, control of tsetse fly population, and minimizing contact with tsetse flies
• Trypanosoma cruzi causes Chagas' disease, limited to South and Central America
• Chagas' disease was first discovered by Brazilian scientist Carlos Chagas
• Trypanosoma cruzi exists in two forms in humans: amastigote and trypomastigote
• Amastigotes are intracellular parasites found in various human tissues
• Trypomastigotes are extracellular and found in peripheral blood
• Diagnosis methods for Chagas' disease include microscopic examination, culture, animal inoculation, histopathology, serodiagnosis, intradermal test, and molecular diagnosis
• Chagas' disease can manifest as acute or chronic forms
• Trypanosoma cruzi completes its life cycle in two hosts: human and reduviid bug
• Nifurtimox and benznidazole are used for treating Chagas' disease
• Prevention and control methods for Chagas' disease include insecticide use, insect repellants, and improvement in housing
• Leishmaniasis is caused by the protozoa of the genus Leishmania
• Leishmaniasis can produce various clinical syndromes ranging from self-healing cutaneous ulcers to fatal visceral disease
• Leishmaniasis primarily affects the reticuloendothelial system
• Leishmaniasis is mainly a zoonotic disease affecting animals like dogs, foxes, jackals, and rodents
• Leishmaniasis is transmitted by the bite of female sandfly vectors
• Leishmania has two subgenera: L. Leishmania and L. Viannia
• Clinical syndromes of leishmaniasis include visceral leishmaniasis, post-kala-azar dermal leishmaniasis, cutaneous leishmaniasis, diffuse cutaneous leishmaniasis, leishmaniasis recidivans, and mucocutaneous leishmaniasis
• Leishmania donovani causes visceral leishmaniasis or kala azar, a major public health problem in many parts of the world
• In humans, the amastigotes of Leishmania donovani are found in the reticuloendothelial system
• The parasite exists in 2 forms:

  • Amastigote form found in humans and other mammals, known as Leishman Donovan (LD) body, intracellular
  • Promastigote form found in the sandfly and in culture
• History of Leishmania donovani:

  • Discovered in 1903 by Sir William Boog Leishman in London and Sir Donovan in Chennai
  • Charles Nicolle characterized the new world visceral leishmaniasis