IH

Apicomplexa (Sporozoa)

Coccidia Sporozoa - Apicomplexa & Microsporidia

Sporozoa

Lack means of locomotion

Life cycle alternates between sexual and asexual stages

Definitive hosts – sexual reproduction

Intermediate hosts – asexual reproduction

Two host life cycle

Terms

Sporogony

  • Sexual reproduction of spores and sporozoites

Schizogony (human host)

  • Asexual multiplication

Paroxysm

  • Toxic material are released form ruptured RBC (allergic response).. shaking chills, high fever, sweating

Coccidia

Pathogenic blood coccidia

  • Plasmodium sp. – malarai
  • Babesia microti
  • Toxoplasma gondii – toxoplasmosis

Pathogenic intestinal coccidia

  • Sarcocystis sp.
  • Cystoisospora belli
  • Cryptosporidium parvum
  • Cryptosporidium hominis
  • Cyclospora cayetanensis

Pathogenic Blood Coccidia

Plasmodium species

P. falciparum

P. vivax

P. ovale

P. malariae

Epidemiology

Causes malaria – one of the most common protozoal diseases in the world – kills 1-2 million/yr

Transmission: by Anopheles mosquito, blood transfusions, or transplacentally

Malaria

Symptoms

  • Splenomegaly, chills, fever, sweats, anorexia, joint pain
  • Leukopenia, normocytic anemia, and hemolytic anemia

Diagnosis

  • ID of species-specific ring forms, gametes, and schizonts on giemsa blood sains (thick and thin smear)

Diagnostic Procedures

Thick Blood Smears

Thin Blood Smears

* Examine at 40x and oil immersion!

Plasmodium falciparum

Malignant malaria

tropics

36 to 48 hrs paroxysms

Infect RBCs (normal size)

Hemolytic anemia – blackwater fever

Diagnostic form are trophs (multiple ring forms) and crescent gametocytes in RBCs

Maurer’s clefts or dots (red)

P. malariae

Quraan malaria

Paroxysms every 72 hrs

Tropics

Diagnostics forms are trophozoite band forms and schizonts (6-12 merozoites that form a rosette)

Color plate:

Plasmodium vivax

Tropics

Tertian malaria

Most prevalent

Paroxysms every 48 hrs

Diagnostic stages are ring forms infecting young RBCs, schuffner’s dots, and schizonts with 12 to 24 merozoites

Color plate:

Plasmodium ovale

Rare, West Africa

Ovale malaria

Paroxysms every 48 hrs

Diagnostics forms are ring forms, oval RBcs, schuffner’s dots, schizonts (8 to 12 merozoites)

Color plate:

Plasmodium Summary

P. falciparum

  • Multiple ring forms (double dot chromatin)
  • Young and old RBC infected
  • Mauer’s dots
  • No schizont observed; gametocytes observed

P. malariae

  • Single ring form (signet ring)
  • Old RBCs infected
  • Troph form band actress RBC
  • Schizont: 6-12 merozoites

P. vivax

  • Single ring form
  • Young RBC infected (retic)
  • Schuffner’s dots
  • Schizont: 12-24 merozoites

Babesia species

Tick transmitted human infection and transfusion

Cases in the U.S.

Fever, chills, sweats, fatigue

Hemolytic anemia, spleen and liver disease

“Maltese cross formation” ring forms

Color plate:

Pathogenic Intestinal Coccidia

Toxoplasma gondii

Definitive host is the domestic cat

Oocysts are shed in cat feces and human become infected via contaminated food, drink, or hand to mouth transmission (cat litter)

Caution for pregnant females

Blood transfusions and organ transplant

Causative agent of toxoplasmosis

Clinical infections:

  • Adults
    • Asymptomatic mostly
    • Mimics Mono
  • Children
    • Rarely: rash myocarditis, encephalomyelitis, hepatitis, retinochoroiditis (blindness)
  • Immunocompromised and congenital are most at risk

Toxoplasma gondii Lab Diagnosis

Encysted tachyzoites in many tissues of the body

  • Biopsy materials

Serology

  • Enzyme immunoassays (EIAs)
  • Titer rise
  • Histology
  • Magnetic resonance imaging (MRI) and computed tomography (CT) scans

PCR

Cryptosporidium parvum & Cryptosporidium hominis

Common infection of cattle, rodents, and fowl

Transmission: ingestion of fecal-contaminated food or water (not killed by chlorine)

Symptoms: abdominal pain and diarrhea, sever in immunocompromised (HIV+)

Diagnosis

  • acid -fast oocyst in feces, ID of organisms in biopsies, serologic tests, Mutli-plex PCR

Cystoisospora belli (Isospora belli)

Opportunistic pathogen

  • Acute infections are clinically indistinguishable from C. parvum
    • Most serious in immunocompromised patients
  • Symptoms
    • Low-grade fever, headache, diarrhea, and colicky abdominal pain
  • Oocyst
    • Elliptical or oval in shape
    • 20 to 33 um long by 10 to 19 um wide

Cyclospora cayetanensis

Transmission

  • Contaminate food & water
  • Humans are the only known host

Symptoms

  • Diarrhea alternating with constipation
  • Anorexia, abdominal cramping, vomiting, low-grade fever, and nausea
    • Self-limiting infection
  • Opportunistic pathogen in immunocompromised host

Microsporidia

The phylum Microspora are often referred to as fungal-related parasites. A vast majority of these organisms are in the process of recategorization and are routinely referred to as ”Microsporidia.” Officallt they have been recategorized as fungi but almost all literature discusses them in the realm of parasites, and so shall we.

Microsporidia Diagnosis

Transmission

  • Soil contaminated with spores from fevers or urine

Symptoms

  • Diarrhea, cramps, loss of appetite, and fatigue
    • Occasionally dehydration and weight loss
  • Immunocompromised and HIV-positive patients
    • Higher risk

Enterocytozoon bieneusi

  • Intestinal and hepatobiliary infections

Encephalitozoon hellem

  • Ocular infections

Encephalitozoon intestinalis

  • Intestinal and disseminated infections