Cryptosporidium parvum

Aka: Cryptosporidium parvum, Cryptosporidium, Cryptosporidiosis, Cryptosporidium hominis, Cryptosporidia

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II. Epidemiology

  1. Cryptosporidium infections in U.S. are more common in summer and fall
  2. Natural Hosts: Young animals (e.g. calves)
    1. C. hominis only infects humans
    2. C. parvum infects both cows, sheep and humans
  3. Foodbourne illness (fecal-oral route transmission)
    1. Common cause of Traveler's Diarrhea worldwide
    2. Contaminated drinking water or uncooked foods
    3. Foods contaminated by an infected food handler
  4. Waterborne Illness outbreaks
    1. Milwaukee contaminated municipal water (n=400,000)
    2. Florida Summer Camp with contaminated outdoor faucet
    3. References
      1. N Engl J Med (1994) 331:161 [PubMed]
      2. MMWR (1996) 45:442-5 [PubMed]
  5. Sexually transmitted in Men who have Sex with Men
    1. Effects 10-20% of advanced HIV patients

III. Risk Factors

  1. Day care center attendance
  2. Children under age 5 years
  3. Human Immunodeficiency Virus (HIV) infection
  4. Men who have Sex with Men
  5. Exposures
    1. Dairy Farmers
    2. Animal contact
    3. Public swiming pools
    4. Contaminated water supply
    5. Travel history

IV. Pathophysiology

  1. Coccidian Protozoan present in animal feces
    1. Farm animals
    2. Domestic pets
  2. Very low inoculum required: 10 Oocysts
  3. Incubation Period 7 to 10 days
  4. Immunocompetent host has only mild Diarrheal illness
  5. Immunocompromised host has potentially severe or even fatal illness (gastrointestinal and respiratory effects)
    1. AIDS patients
      1. CD4 Count <200: Chronic, persistent Diarrhea
      2. CD4 Count <140: More severe symptoms

V. Symptoms

  1. Normal Host (typically resolves within 2 weeks)
    1. Diarrhea
    2. Abdominal Pain
    3. Nausea or Vomiting
    4. Fever
  2. HIV Infection or other Immunocompromised patient (prolonged illness)
    1. Chronic, persistent, secretory, watery Diarrhea
    2. Cough
    3. Abdominal Pain
    4. Weight loss
    5. Fatigue
    6. Joint Pain

VI. Labs

  1. Specific Ova and Parasite testing
    1. Cryptosporidium is not typically included on routine Ova and Parasite testing
    2. Request specific testing if higher index of suspicion
    3. May require multiple stool samples collected on several different days (intermittent excretion)
  2. Diagnostic modalities
    1. PCR (gold standard)
    2. Microscopy with Immunohistologic testing (immunofluorescence against oocyst wall)
      1. Test Sensitivity and Test Specificity approaches 100%
    3. Microscopy (wet mount, stains)
  3. Sample sources
    1. Stool
    2. Duodenal aspirate
    3. Bile secretions
    4. Respiratory secretions
  4. Other tests
    1. Serum Alkaline Phosphatase
      1. Increased if biliatry tract involvement
    2. Abdominal imaging (CT Abdomen, Abdominal Ultrasound)
      1. May demonstrate gallbladder enlargement and bile duct dilitation

VII. Course

  1. Symptom onset delayed 2-10 days from exposure (up to 2 weeks)
  2. Normal host (self-limited)
    1. Diarrhea persists for 10 days in normal host (self limited)
    2. May relapse over weeks to months in some cases
  3. Immunocompromised host
    1. Severe course (may be fatal)
    2. Stools may exceed 21 stools per day for months (with secondary malabsorption and Failure to Thrive)

VIII. Complications

  1. Reactive Arthritis (associated with C hominis)
  2. Extra-intestinal infection (Immunocompromised patients)
    1. Lungs are commonly affected (with secondary cough), esp. with C. hominis
    2. Chronic biliary tract disease (sclerosing Cholangitis) in patients with comorbid HIV Infection
    3. Other involvement
      1. Conjunctivitis
      2. Esophagitis
      3. Appendicitis
      4. Pancreatitis
      5. Intestinal perforation

IX. Management

  1. Symptomatic management
    1. See Acute Diarrhea
    2. Most immunocompetent patients recover within 7-14 days without specific treatment
    3. Maximize hydration
  2. Immunocompetent patients with severe or prolonged Diarrhea (>7 days)
    1. Paromomycin and Azithromycin are NOT thought to be effective
    2. Nitazoxanide (Alinia)
      1. Child age 1 to 3 years: 100 mg orally twice daily for 3 days
      2. Child age 4 to 11 years: 200 mg orally twice daily for 3 days
      3. Adult (or age >11 years): 500 mg orally twice daily for 3 days
      4. Cure rate 72 to 80% with treatment, and resolves spontaneously in most cases
  3. Immunocompromised patients or HIV positive
    1. Nitazoxanide (Alinia) is no more effective than Placebo in Immunocompromised patients
      1. However may be trialed in age over 1 year old
      2. Paromomycin and Azithromycin may be trialed in refractory cases (but low efficacy)
    2. Highly Active Antiretroviral Therapy in HIV eradicates intestinal Cryptosporidium (especially if CD4 >150 cells/mm3)
      1. Protease Inhibitors may have additional activity against Cryptosporidium

X. Prevention

  1. Avoid swimming for 1-2 weeks after exposure
    1. Oocyst sheddling continues after resolution
  2. Water sterilization
    1. Water microfilters (1 micron pore)
    2. Water boiling (for >1 minute) reduces infection risk
      1. Some guidelines recommend boiling for 10 minutes
    3. Freeze water
    4. Ammonia or formalin in high concentration purifies water
  3. Cryptosporidium is very resistant to halogens (e.g. chlorination, Iodine)
    1. Swimming pool chlorination does NOT prevent transmission
    2. Cryptosporidium oocysts survive >10 days in swimming pools chlorinated to CDC recommended levels
    3. Shields (2008) J Water Health 6(4): 513-20 [PubMed]

XI. Resources

  1. Cryptosporidium
    1. http://www.cdc.gov/parasites/crypto/

XII. References

  1. Wang and Nguyen (2017) Crit Dec Emerg Med 31(9):13-8
  2. Checkley (2015) Lancet Infect Dis 15(1): 85-94 [PubMed]
  3. Perkins (2017) Am Fam Physician 95(9):554-60 [PubMed]
  4. Pyzocha (2023) Am Fam Physician 108(5): 487-93 [PubMed]
  5. Weller (2001) BMJ 322:1350-4 [PubMed]

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