Updated: 6/7/2019

Plasmodium

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Snapshot

  • A 25-year-old woman presents to the clinic with a one-week history of continuous high-grade fevers, myalgia, chills, and night sweats. She recently returned to the United States after volunteering with the Peace Corps in Nigeria. Her temperature is 103.2°F (39.6°C) and physical reveals a palpable spleen. A peripheral blood smear is shown.
Introduction
  • Epidemiology
    • geography
      • endemic throughout most of the tropics
      • disproportionately high burden of malaria in Sub-Saharan Africa
    • prevalence
      • WHO estimated 216 million cases of malaria in 91 countries in 2016
    • risk factors
      • exposure to Anopheles mosquitos, particularly at dusk and dawn
  • Pathogenesis
    • transmission
      • through bites of female Anopheles mosquitos
    • Plasmodium life cycle involves two hosts: human and Anopheles mosquito 
      • human host
        • sporozoite stage
          • the Plasmodium-infected Anopheles mosquito inoculates sporozoites into the human host during a blood meal
          • sporozoites infect hepatocytes and mature into schizonts, which rupture and release merozoites  
        • hypnozoite stage
          • for Plasmodium vivax and Plasmodium ovale, a dormant stage (hypnozoites) can persist in the liver and cause relapses
        • merozoite and trophozoite stage
          • merozoites undergo asexual multiplication in erythrocytes
          • merozoites reform to become trophozoites, which are ring-shaped
        • schizont stage
          • trophozoites undergo division to form large multi-nucleated schizonts
          • the schizont ruptures releasing merozoites
            • rupture of erythrocytes correlates with fever spikes
        • gametocyte stage
          • some parasites differentiate into sexual gametocytes, which are the form of the parasite that is ingested by an Anopheles mosquito
      • Anopheles mosquito host
        • oocyst stage
          • male and female gametocytes fuse in the stomach of the mosquito to form an oocyst
        • sporozoite stage
          • the oocyst divides into many sporozoites, which are then inoculated into the human host to begin the cycle anew
    • 4 main speces of Plasmodium cause malaria
      • Plasmodium falciparum 
        • irregular fever patterns
      • Plasmodium vivax
        • 48-hour fever cycle
      • Plasmodium ovale
        • 48-hour fever cycle
      • Plasmodium malariae
        • 72-hour fever cycle
  • Associated conditions
    • occlusion of capillaries in the brain (cerebral malaria), kidneys, and lungs (Plasmodium falciparum)
 Presentation
  • Symptoms
    • fever
    • headache
    • anemia
    • splenomegaly
  • Physical exam
    • palpable spleen
    • conjunctival pallor
Studies
  • Labs
    • Peripheral blood smear shows trophozoites and schizonts within erythrocytes 
      • trophozoite ring form within erythrocyte
      • schizont containing merozoites
      • red granules throughout cytoplasm in erythrocytes seen with Plasmodium vivax and Plasmodium ovale
  • Making the diagnosis
    • most cases are clinically diagnosed
Differential
  • Babesiosis
    • differentiating factor
      • predominantly in northeastern United States
  • Trypanosomiasis
    • differentiating factors
      • lymphadenopathy, somnolence, coma
  • Borrelia recurrentis
    • differentiating factor
      • history of tick exposure
Treatment
  • Medical
    • chloroquine
      • used in areas with low drug resistance
    • mefloquine  
      • used in areas with high rates of chloroquine resistance
    • atovaquone/proguanil or artemether-lumefantrine
      • used in areas with high rates of chloroquine resistance
        • first-line treatment for P. falciparum resistant to chloroquine
    • primaquine
      • used to kill latent hypnozoites in Plasmodium vivax and Plasmodium ovale infection
    • intravenous quinidine or artesunate
      • used in life-threatening situations
Complications
  • Cerebral malaria
    • complication of Plasmodium falciparum infection
    • parasitized erythrocytes occlude capillaries in the brain
  • Renal failure
    • complication of Plasmodium falciparum infection
    • parasitized erythrocytes occlude capillaries in the kidney
 

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Questions (3)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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