C

• Sporozoan


  Opportunistic & Coccidian
• Hemoflagellates


  Three orders: Eimeriida, Haemosporida, and Piroplasmida
• Eimeriida


  • Toxoplasma
  • Cryptosporidium
  • Cyclospora
  • Isospora
  • Sarcocystis
• Toxoplasma gondii


  Obligate intracellular parasite
• Toxoplasma gondii


  • Tachyzoite - asexual, crescent shaped, contains dense granules and round nucleus
  • Tissue cyst - asexual, resting stage containing slowly multiplying trophozoites (bradyzoites)
  • Oocyst - sexual, surrounded by a refractile and resistant double layered colorless cyst wall
• Toxoplasma gondii life cycle


  1. Felines - sexual life cycle

  2. Humans - asexual life cycle
• Toxoplasmosis in Immunocompetent Patients


  • IFN-γ, and stimulation of CD8+ cytotoxic T lymphocytes
  • Lymphadenopathy
  • Rare complications are maculopapular rash, pneumonia, myocarditis and encephalopathy
• Toxoplasmosis in Immunocompromised Patients

  • Toxoplasma encephalitis
  • Congenital Toxoplasmosis - chorioretinitis leading to profound visual impairment
• Laboratory Diagnosis of Toxoplasmosis


  • Direct Microscopic Examination
  • Antibody detection
  • Detection of Toxoplasma Antigens
  • Molecular diagnosis
  • Animal inoculation
  • Tissue culture
  • Imaging methods
• Diagnosis of Congenital Toxoplasmosis


  • Toxoplasma antigens in amniotic fluid
  • Toxoplasma specific genes by PCR
  • IgM antibodies in fetal blood
  • IgA antibodies in fetal blood
  • Isolation of the parasite
  • Ultrasound of fetus
• Prevention of Toxoplasmosis


  • Consumption of thoroughly cooked meat
  • Proper hygiene maintenance and hand cleaning
  • Regular prenatal and antenatal screening
  • Avoiding cat's feces contaminated materials
  • Screening of blood banks or organ donors
• Cryptosporidium parvum


  Intestinal coccidian
• Cryptosporidium parvum


  • Oocyst - round, small, 4–6 µm in size, surrounded by a cyst wall and bears four sporozoites
  • Thick walled oocyst - contains two electrodense cyst wall with an electroluscent middle zone
  • Thin walled oocyst - surrounded by a single layered membrane
• Cryptosporidium parvum life cycle


  1. Ingestion of food and water contaminated with feces containing thick walled oocysts

  2. Autoinfection: Thin walled oocyst can infect the same host

  3. Oocyst – sporozoites – trophozoites – Type I meront – Type II meront – Micro and macrogamont – Zygote – Thick walled and Thin walled oocyst
• Cryptosporidiosis in Immunocompetent Hosts


  • Asymptomatic
  • Accounts for 2–6% of cases of traveler's diarrhea
• Cryptosporidiosis in Immunocompromised Hosts


  • Chronic, persistent remarkably profuse diarrhea (1–25 L/day), leading to significant fluid and electrolyte loss
• Laboratory Diagnosis of Cryptosporidiosis


  • Direct Microscopy - double walled 4–6 µm size oocyst
  • Antigen detection from Stool
  • Antibody detection
  • Molecular
• Cyclospora cayetanensis


  Similar life cycle with C. parvum, self limiting diarrhea
• Isospora beli


  Oval/elliptical oocyst, 23 to 36 μm × 12 to 17 µm in size, contains two sporocysts, each with four sporozoites
• Isospora beli life cycle


  Ingestion of food and water contaminated with sporulated oocyst – sporozoites – trophozoites – schizont – merozoites – microgametocytes and macrogametocytes – zygotes – oocyst
• Isospora beli clinical features


  • Chronic, profuse watery diarrhea and extraintestinal infections such as involvement of biliary tract (HIV)
• Sarcocystis spp.


  • Intestinal sarcocystosis: S. hominis and S. suihominis
  • Muscular sarcocystosis: Caused by unidentified species of Sarcocystis (S. lindemanni)
• Sarcocystis morphology


  • Oocyst - elongated, oval, colorless thin walled (< 1µm), measures 13–19 µm in S.hominis and 10–13 µm in S. suihominis
  • Sporocyst - released and excreted in the feces of definitive host
  • Sarcocyst - muscular cysts and skeletal muscles, divided into many compartments that contain numerous banana shaped bradyzoites or metrocytes
• Sarcocystis life cycle


  1. DH - carnivorous/predator animal

  2. IH - muscle and other tissues of the herbivorous/prey animal

  3. Intestinal Sarcocystosis: DH - Man, IH - Pig (S. hominis)/cattle (S. hominis)

  4. Muscular Sarcocystosis: IH - man, ingestion of food and water contaminated with sporocysts excreted in the feces of dogs and cats
• Sarcocystosis clinical features


  • Intestinal Sarcocystosis - usually asymptomatic but patient may develop nausea, vomiting, abdominal pain and diarrhea
  • Muscular Sarcocystosis - Symptoms depend on the size of the muscle cysts that varies from 50 µm to 5 cm
• Laboratory Diagnosis of Sarcocystosis


  • Intestinal Sarcocystosis: Stool exam - Sporocyst
  • Muscular Sarcocystosis: Histological examination - sarcocysts, Serology - Detecting antibodies using Western blot
• Sporozoa includes two classes: Apicomplexa (eukaryotic parasites) and Microspora (heterokont protists).