MICROPARA: PROTOZOAL INFECTIONS

• Parasitism


  A symbiotic relationship that is of benefit to one party or symbiont (parasite) at the expense of the other party (host)
• Definitive Host


  The one that harbors the adult or sexual stage of the parasite or the sexual phase of the life cycle
• Intermediate Host


  Harbors the larval or asexual stage of the parasite or the asexual phase of the life cycle
• Ectoparasites


  Parasites that live outside the host's body
• Ectoparasites


  • Arthropods such as mites, ticks, and lice
• Endoparasites


  Parasites that live inside the host's body
• Endoparasites


  • Parasitic protozoa and Helminths

  
• Accidental Host


  A living organism that can serve as a host in a particular parasite's life cycle
• Facultative Parasites


  Organisms that can be parasitic but do not have to live as a parasite and are capable of living an independent life apart from the host
• Facultative Parasites


  • Free living amoebae that cause keratoconjunctivitis and primary amoebic meningoencephalitis
• Obligate Parasite


  Must be a parasite in order to survive
• Obligate Parasites

  • Most parasites that infect humans
• Parasitology


  Study of parasites
• Parasitologist


  Someone who studies parasites
• Medical Parasitology


  The study of parasites that cause human disease

  
• Ways in which parasites cause disease

  • Toxins produced
  • Harmful enzymes
  • Physical damage to tissues and organs
  • Occludes blood vessels and other tubular structures
  • Interferes with vital processes of the host
  • Deprives the host of essential nutrients
• Protozoa


  • Most are unicellular, but some are multicellular (colonial)
  • Can be classified taxonomically by their mode of locomotion (pseudopodia, flagella, cilia, non-motile)
  • Not all protozoa are parasitic
• Facultative Parasites (Protozoa)


  Capable of free living non-parasitic, however they can become parasites if they accidentally gain entrance to the body
• Facultative Parasitic Protozoa


  • Acanthamoeba spp and Naegleria fowleri

  
• Characteristics of Protozoa


  • They are tiny
  • Infections caused by protozoa are often diagnosed with microscopic examination of fluids, tissue specimens or feces
• Trophozoites


  The motile, feeding, dividing stage in the protozoan's life
• Cysts, oocysts or spores

  Dormant stages of protozoa
• Entry of Protozoa


  • Primarily acquired by inhalation or ingestion of oocysts or spores
  • Injection via the bite of an infected arthropod
• There are only 5 nationally notifiable parasitic diseases, 4 of them are Protozoal diseases and one helminth disease (Cryptosporidiosis, Cyclosporiasis, Giardiasis, malaria, trichinellosis)

  
• Parasitic infections are most often diagnosed by observing and recognizing a particular life cycle stage in a clinical specimen

  
• Not all parasites cause disease but they can deprive the host of nutrients and it is detrimental to the host
• Parasitic protozoal infections are diagnosed by observing trophozoites, cysts, oocysts or spores

  
• Giemsa Stain is used to stain peripheral blood smears, Trichrome, Iron Hematoxylin, Acid Fast Stain are used to stain fecal specimens
• Leishmaniasis has 3 forms: cutaneous, visceral (Kala-Azar), and mucocutaneous
• Amebic Conjunctivitis and Keratoconjunctivitis are amebic eye infections caused by several species of amoebas in the genus Acanthamoeba
• Toxoplasmosis is a systemic sporozoan infection that can be serious or fatal in immunodeficient persons

  
• Amebiasis/Amebic Dysentery is caused by Entamoeba histolytica and can be fatal if left untreated
• Balantidiasis is caused by the ciliated protozoan Balantidium coli and occurs more commonly in pigs than in humans
• Cryptosporidiosis is caused by the coccidial protozoan Cryptosporidium parvum and can be prolonged, fulminant and fatal in immunosuppressed patients
• Cyclosporiasis is caused by the coccidian Cyclospora cayetanensis and can cause prolonged diarrhea in immunocompetent and immunocompromised patients
• Giardiasis infects the duodenum and can cause a range of symptoms from asymptomatic to severe
• Diarrhea duration


  9 to 43 days in immunocompetent patients, months for immunocompromised patients
• Patient care


  Use standard precautions for hospitalized patients
• Occurrence locations


  • Asia, Carribean, Mexico, Peru and US
• Cyclospora cayetanensis


  A coccidian