Updated: 12/15/2018

CNS Infections of Protozoa

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Snapshot
  • A 56-year-old nurse is brought to the emergency room for altered mental status. She spent a year in West Africa volunteering at a hospital. She returned to the US about 4 weeks ago. At that time, she had intermittent fevers with general malaise and a transient urticarial rash and noted a bug bite on her right forearm. She was then treated for malaria, though diagnostic testing was equivocal. In the past week, she became increasingly somnolent during the day. She also lost 15 lbs within the past 2 weeks. A lumbar puncture is done and diagnostic studies are sent. Meanwhile, she is started on empiric therapy. (African sleeping syndrome caused by Trypanosoma brucei)
Introduction
  • Protozoa
    • single-celled eukaryotes, often parasitic, that feed on organic tissues
Infections of Protozoa
Central Nervous System
Gastrointestinal
Visceral Infections
Hematologic Infections Sexually Transmitted Diseases
  • Toxoplasma gondii
  • Naegleria fowleri
  • Trypanosoma brucei
  • Acanthamoeba
  • Giardia lamblia
  • Entamoeba histolytica
  • Cryptosporidium
  • Trypanosoma cruzi
  • Leishmania donovani
  • Plasmodium
  • Babesia
  • Trichomonas vaginalis
 
Toxoplasma gondii
  • Introduction
    • clinical syndrome
      • toxoplasmosis
    • reservoirs
      • domestic cats
    • transmission
      • ingestion of cysts in meat
      • ingestion of food contaminated with oocysts from cat excretion
      • can be transmitted via placenta to neonate
        • congenital toxoplasmosis
          • triad of chorioretinitis, hydrocephalus, and intracranial calcifications
    • pathogenesis
      • tachyzoites are rapidly reproductive and invasive
      • cysts are slow-dividing and latent, arising 1 week after infection
        • can remain in hosts for a lifetime in the CNS
      • oocysts contain sporozoites, can spread them to other hosts, and can survive in the environment for up to a year
    • risk factors
      • exposure to cats
  • Presentation
    • immunocompetent patients
      • mononucleosis-like syndrome
    • immunosuppressed patients
      • brain abscesses
      • focal neurologic deficits including aphasia, hemiparesis, and seizures
  • Imaging and studies
    • serologic detection of immunoglobulins with enzyme linked immunosorbent assay (ELISA)
    • microscopy showing tachyzoites in blood or cerebral spinal fluid (CSF)
    • brain MRI
      • multiple ring-enhancing lesions
  • Treatment
    • sulfadiazine and pyrimethamine
      • immunosuppressed patients
Naegleria fowleri
  • Introduction
    • clinical syndrome
      • meningoencephalitis
    • risk factors
      • swimming in warm freshwater
    • pathogenesis
      • protozoa enters the CNS via cribriform plate
    • prognosis
      • fatal in majority of cases within 1 week
  • Presentation
    • sudden headache
    • photophobia and stiff neck
    • altered sense of taste or smell
    • nose bleeds
    • altered mental status
  • Imaging and studies
    • cerebral spinal fluid
      • presence of amoebas
      • elevated pressure
    • culture and direct fluorescence antibody stain
    • brain CT
      • obliteration of cisternae and subarachnoid spaces
  • Treatment
    • amphotericin B
Trypanosoma brucei
  • Introduction
    • clinical syndrome
      • African sleeping sickness or African trypanosomiasis
    • transmission via tsetse fly bite
    • demographics
      • endemic to sub-Saharan Africa
    • prognosis
      • good prognosis if treated appropriately
  • Presentation
    • early stage
      • chancre at bite site
      • intermittent fevers, malaise, myalgia, and arthralgia
      • lymphadenopathy
      • facial edema
      • transient rash (urticarial or macular) 2 months after onset
    • late stage
      • persistent headaches
      • daytime somnolence and nighttime insomnia (African sleeping sickness)
      • weight loss
  • Imaging and studies
    • peripheral blood smear with trypomastigotes
    • card agglutination test for trypanosomiasis (CATT)
      • results available immediately
      • high sensitivity (96%)
    • lymph node biopsy
    • CSF studies
      • visualization of trypanosome
      • detection of immunoglobulins
  • Treatment
    • suramin
      • for early stage disease
    • melarsoprol
      • for late stage disease or CNS involvement
Acanthamoeba
  • Introduction
    • clinical syndrome
      • granulomatous amoebic encephalitis
    • risk factors
      • immunosuppression
    • transmission
      • via nasopharyngeal or breaks in skin
    • pathogenesis
      • cysts are dormant and resistant to treatment
      • trophozoites are infective and replicate via fission
    • prognosis
      • high rate of mortality
  • Presentation
    • headache
    • photophobia and stiff neck
    • altered mental status
    • skin lesions
      • ulcers, nodules, or abscesses
  • Imaging and studies
    • cerebral spinal fluid
      • presence of amoebas
      • elevated pressure
    • brain CT
      • nonspecific findings of single or multiple low-density masses with hydrocephalus
    • brain or skin biopsy
      • granulomas, necrosis, amoebas, and inflammatory infiltrates
  • Treatment
    • no first-line treatment is recommended
    • a combination of antibiotics and antifungals are usually used
  • Complications
    • residual vision or hearing impairment
 

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Questions (2)
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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(M1.MC.50) A 41-year-old male with a history of pneumocystis jiroveci pneumonia is found to have multiple ring-enhancing lesions on brain CT. Which of the following is most likely responsible for this patient's abnormal scan? Review Topic

QID: 101509
1

Neoplasm

6%

(2/31)

2

Bacteria

13%

(4/31)

3

Virus

6%

(2/31)

4

Prion

0%

(0/31)

5

Protozoa

68%

(21/31)

M1

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