Lan

• Parasite


  An organism that lives on or in a host organism and gets its food from or at the expense of its host
• Three main classes of parasites

  • Protozoa
  • Helminths
  • Ectoparasites
• Protozoans


  • Unicellular
  • Aerobic heterotrophs
  • Many intestinal protozoa are capable of anaerobic growth
• Protozoans


  • Asexual reproduction: binary fission, budding, multiple fission
  • Sexual reproduction: conjugation, gamete formation
• Cyst


  A protective capsule produced by some protozoa under adverse conditions, enabling the organism to survive
• Oocyst


  Cyst formed by members of the phylum Apicomplexa, used to produce new cells asexually
• Trophozoite


  The active, feeding, multiplying stage of most protozoa, usually associated with pathogenesis
• Infective stage


  The stage in the life cycle at which the parasite is able to initiate an infection in its host
• Diagnostic stage


  The stage at which the parasite leaves the host, e.g. through excretion
• Classification of protozoans


  • Mastigophora (flagellated)
  • Sarcodina (amoeboids)
  • Sporozoa (sporozoans)
  • Infusoria
• Mastigophora (flagellated protozoans)


  • Parasites or free-living
  • Have flagella for locomotion
  • Body covered by a cuticle or pellicle
  • Freshwater forms have a contractile vacuole
  • Reproduction by binary fission
• Sarcodina (amoeboids)


  • Live in freshwater, sea or moist soil
  • Movement by pseudopodia
  • Capture prey by pseudopodia
  • No definite shape, no pellicle
  • Contractile vacuole present in freshwater forms
  • Reproduction by binary fission and cyst formation
• Sporozoa (sporozoans)


  • Endoparasitic
  • No specialised organ for locomotion
  • Pellicle present with subpellicular microtubules for movement
  • Reproduction by sporozoite formation
• Infusoria are aquatic and move actively with the help of thousands of cilia
• Examples of Protozoa


  • Trypanosoma
  • Trichomonas
  • Giardia
  • Leishmania
• Sarcodina or Amoeboids


  • They live in the freshwater, sea or moist soil
  • The movement is by pseudopodia
  • They capture their prey by pseudopodia
  • There is no definite shape and pellicle is absent
  • The contractile vacuole is present in the amoeboids living in freshwater
  • Reproduction is by binary fission and cyst formation
• Sarcodina or Amoeboids


  • Amoeba
  • Entamoeba
• Sporozoa or Sporozoans


  • They are endoparasitic
  • They don't have any specialised organ for locomotion
  • The pellicle is present, which has subpellicular microtubules, that help in movement
  • Reproduction is by sporozoite formation
• Sporozoa or Sporozoans


  • Plasmodium
  • Myxidium
  • Nosema
  • Globidium
• Infusoria


  • They are aquatic and move actively with the help of thousands of cilia
  • They have fixed shape due to covering of pellicle
  • They may have tentacles, e.g. in the sub-class Suctoria
  • Contractile vacuoles are present
  • Some species have an organ for defence called trichocysts
  • They move with the help of cilia and the movement of cilia also helps in taking food inside the gullet
  • They reproduce by transverse division and also form cysts
• Infusoria


  • Paramecium
  • Vorticella
  • Balantidium
• Trichomonas vaginalis


  Causative organism of Trichomoniasis, a sexually transmitted disease (STD)
• Trichomoniasis


  Sexually transmitted disease (STD)
• Pathogenesis of Trichomoniasis


  • Destroys epithelial cells and cytotoxic substances are released
  • Vaginal pH increases and the number of leukocytes also increases in response to the toxic substance released by the pathogen
• Symptoms of Trichomoniasis


  • Itching and burning in genital organs and discharge
  • Mostly asymptomatic in males, but in females it may lead to many complications such as complication during pregnancy and after birth
• Entamoeba histolytica


  • Infective stage: mature cyst
  • Diagnostic Stage: Cyst and trophozoite
• Amoeba


  • Virulence Factor: Lectin - mediates attachment to the galactose part of the plasma membrane and causes cell lysis
  • Amebapores - used to penetrate
• Diseases caused by Amoeba


  • Amebiasis - Amebic Dysentery - severe form of amebiasis associated with stomach pain, bloody stools (poop), and fever
  • Amebic Liver Abscess (ALA) - rare
• Signs and symptoms of Amebiasis

  • Fever, Abdominal cramping and pain
  • Mucoid stool with blood, Loose bowel movement
• Diagnostic Test for Amoeba

  • Direct Microscopy of stool
  • Blood test is also available but is only recommended when your healthcare provider thinks that your infection may have spread beyond the intestine (gut) to some other organ of your body, such as the liver
• Mode of Transmission of Entamoeba histolytica

  • Feco-Oral Route
  • Puts anything into their mouth that has touched the feces (poop) of a person who is infected with E. histolytica
  • Swallows something, such as water or food, that is contaminated with E. histolytica
  • Swallows E. histolytica cysts (eggs) picked up from contaminated surfaces or fingers
• Risk Factors for Amoeba


  • More common in people who live in tropical areas with poor sanitary conditions
  • People who have traveled to tropical places that have poor sanitary conditions
  • Immigrants from tropical countries that have poor sanitary conditions
  • People who live in institutions that have poor sanitary conditions
  • Men who have sex with men
• Treatment for Amebiasis


  • Metronidazole - for invasive amebiasis
  • Diloxanide furoate - for asymptomatic carriers
• Prevention of Amebiasis


  • Drink bottled water with an unbroken seal, tap water that has been boiled for at least 1 minute, carbonated (bubbly) water from sealed cans or bottles, or carbonated (bubbly) drinks (like soda) from sealed cans or bottles
  • Make tap water safe for drinking by filtering it through an "absolute 1 micron or less" filter and dissolving chlorine, chlorine dioxide, or iodine tablets in the filtered water
  • Thorough handwashing with soap and water after using the toilet, after changing diapers, and before handling or preparing food
• Plasmodium


  • Causative organisms: P. falciparum (deadliest, most prevalent in Africa), P. vivax (Sub-Saharan Africa), P. malariae, P. ovale, P. knowlesi
  • Infective stage: sporozoites
  • Vector: Female Anopheles mosquito
• Pathogenesis of Malaria


  The parasite attacks the liver and RBCs. It multiplies within liver cells, enters the bloodstream and ruptures RBCs. It releases a toxic substance called 'hemozoin', which causes fever.
• Disease caused by Plasmodium

  Malaria - serious and sometimes fatal disease caused by a parasite that commonly infects a certain type of mosquito which feeds on humans
• Mode of Transmission of Malaria

  • Mostly spreads to people through the bites of some infected female Anopheles mosquitoes
  • Blood transfusion and contaminated needles may also transmit malaria
• Diagnosis of Malaria


  Direct Microscopy: Thin and thick smears with Giemsa or Wright's stain - Better yield if blood samples are taken during fever or 2-3 hours after peak
• Signs and Symptoms of Malaria

  • Most common: fever, headache, and chills (usually starts within 10-15 days of getting bitten by an infected mosquito)
  • Severe symptoms include: extreme tiredness and fatigue, impaired consciousness, multiple convulsions, difficulty breathing, dark or bloody urine, jaundice (yellowing of the eyes and skin), abnormal bleeding