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Tufts OpenCourseware
Author: Amelia Virostko

1. Apicomplexan parasites

  1. Apical complex in zoite stage
  2. Plasmodium, Babesia, Crytosporidium, Toxoplasma
  3. Discharge antigens for zoite motility, attachment, invasions, and replication

2. Malaria

  1. 4 Plasmodium species: P. falciparum, P. ovale, P. vivax, and P. malariae
  2. Life cycle
    1. Anopheles mosquito injects sporozoites into bloodstream
    2. Sporozoites invade hepatocytes and replicate to form merozoites
      1. P. vivax and P. ovale can form hynozoites
    3. Merozoites invade RBC and begin schizogony to form multiple merozoites
    4. Merozoites released into bloodstream to invade more RBC
    5. Feeding mosquito ingests male and female gametocytes, where they undergo reproduction
  3. Uncomplicated malaria
    1. Classic (rare) attack lasts 6-10
    2. Symptoms
      1. cold stage: cold and shivering
      2. hot stage: fever, headache, vomiting, seizures
      3. sweating stage: sweats, fatigue
      4. attacks every 3rd day with quartan parasite (P. malariae) and every 2nd day with other species
    3. More commonly present with: fever, chills, sweats, headaches, nausea and vomiting, body aches, general malaise
    4. P. falciparum malaria may also include jaundice, hepatomegaly, and increased respiratory rate
  4. Severe Malaria
    1. Neurologic symptoms: altered behavior, seizures, coma, impairment of consciousness
    2. Severe anemia and hemoglobinuria secondary to hemolysis
    3. Pulmonary edema or ARDS
    4. Coagulopathies and thrombocytopenia
    5. Cardiovascular shock and collapse
    6. Acute renal failure
    7. Metabolic acidosis with hypoglycemia
    8. Often in persons with no immunity to malaria, young children, and pregnant women
    9. Cerebral malaria from P. falciparum
  5. Virulence Factors
    1. 1. Duffy blood group antigen: P. vivax binds on RBC to gain entry
      1. Africans are Duffy negative therefore resistant to this strain
    2. PfEMP1: P. falciparum uses to gain entry into RBC
      1. CSA variant can sequester in the placenta, therefore causes recrudescence in woman’s first pregnancy
  6. Host Genetics
    1. Sickle cell heterozygotes protected from malaria
    2. Innate host resistance also conferred from glucose-6-phosphate dehydrogenase deficiency, beta-thalassemia, and ovalocytosis
  7. Diagnosis and Identification
    1. Giemsa-stained blood smear
    2. If initial test is negative, repeat 6 hours later if strong suspicion exists
  8. Treatment and Prevention
    1. Acquired partial immunity
      1. species and strain specific
      2. develops after long exposure and very low parasitemia
    2. Many parasites now resistant to common antimalarial drugs
      1. chloroquine effective against all strains except P. falciparum, however South American strains are still susceptible
      2. mefloquine, quinine, quinidine, or fansidar to treat chloroquine-resistant strains
      3. chloroquine, mefloquinine, and doxycycline used as chemoprophylaxis
      4. primaquine treats hypnozoite stage of infection

3. Babesia

  1. Intraerythrocytic protozoal parasite
  2. Ixodes scapularis ticks inject sporozoites into blood, where they immediately invade RBC to begin cycles of merogony
  3. Endemic to same areas as Lyme disease during summer
  4. Present with flu-like illness with fever, chills, sweats, muscle aches, and fatigue
  5. Severe infection in splenectomy patients
  6. Identify as tetrads of small rings with Giemsa-stain
  7. Treat with quinine plus clindamycin