• Transmission occurs when oocysts contaminating food or water are ingested or, more commonly, through fecal-oral transmission from person to person.
• The infectious dose for humans is low, estimated at less than 10 oocysts. The incubation period is approximately 5 to 21 days and oocyst shedding may occur for weeks to months.
• Invasion of intestinal epithelial cells of the upper gastrointestinal tract leads to a secretory diarrhea. The exact mechanism by which this occurs is still unclear.

• Typically children under 5 years of age are most often affected. Severe disease is usually seen in the immunocompromised; such as patients with impaired cell mediated immunity (in particular those who are HIV positive or taking immunosuppressive medications), those with immunoglobulin deficiencies as well as gamma interferon deficiencies.
• A significant seasonality has been reported, with peaks occurring in North America during the late summer and early fall.
• Outbreaks have been associated with swimming pools, lakes, water recreation parks, drinking water supplies, day camps, unpasteurized apple cider, exposure to farm animals, and day care attendance.
• Other risk factors include exposure to dogs, cats, deers, cockroaches, and traveling abroad.

• In immunocompromised patients, infection can lead to severe protracted diarrhea with malnutrition and wasting. Biliary tract disease and systemic dissemination such as pulmonary disease can also be seen in the immunocompromised.

• For immunocompetent hosts, gastrointestinal disease is self-limited usually lasting 10 to 14 days. Supportive therapy is usually all that is necessary.
• For immunocompromised patients, diarrhea can be severe, debilitating, and often life-threatening. Aggressive supportive therapy is usually required along with a trial of antimicrobial therapy. Unfortunately, there are no agents that are uniformally effective against Cryptosporidium parvum.

• Viral gastroenteritis including but not limited to:
  • Rotavirus
  • Adenovirus
  • Astrovirus
  • Norwalk
  • Cytomegalovirus (CMV)
• Bacterial gastroenteritis including but not limited to:
  • Salmonella
  • Shigella
  • Yersinia
  • Campylobacter
  • Aeromoas
  • Pleisomonas
  • Enterotoxigenic E. coli
  • Vibrio cholerae
• Parasitic gastroenteritis including but not limited to:
  • Giardia
  • Entamoeba
  • Cyclospora
  • Isospora
  • Microsporidia
  • Dientamoeba fragilis
  • Blastocystis hominis
  • Clostridium difficile enterocolitis

• Allergic
• Autoimmune
• Anatomical
• Endocrine
• Iatrogenic/Medications
• Inflammatory bowel disease
• Malabsorption
• Neoplastic

• Onset: Acute onset of watery non-bloody diarrhea, crampy abdominal pain, low-grade fever, and occasionally nausea and vomiting.
• Exposure: Exposure to ill contacts, public swimming pools, lakes or wave parks, animals, day care attendance, travel history, dietary history such as consumption of unpasteurized beverages and drinking water supply.
• Evidence of immunosuppression: Immunosuppression secondary to disease or medication as well as exposure to immunosuppressed individuals in the household or, if patient is old enough, through occupation.

Test: Modified acid fast stain
Significance: Diagnosis is made by observing the 4 to 5 µm cysts in preserved stool specimens. Immunofluorescent antibody or rapid (3 minute) direct antigen detection tests are also available. Stool specimens should be performed three times on alternate days to exlude the diagnosis.

Test: Must specifically request that the microbiology lab test for this organism.
Significance: A recent national survey of clinical laboratories revealed only 5% routinely tested for C. parvum.

Test: Sputum specimen
Significance: For respiratory infections, diagnosis is made by finding the oocysts in sputum specimens.

Test: H and E staining of small intestinal biopsies
Significance: May show the organism protruding from the microvillus border of enterocytes.

• Fluid and electrolyte replacement. For protracted cases, patients will eventually require hyperalimentation.
• The antibiotic paromomycin, an aminoglycoside, can improve symptoms and decrease parasite excretion in the feces of some immunocompromised patients and this has become the treatment of choice for immunosuppressed patients. The dosage is 25 to 30 mg/kg/day three times a day for 7 days. Spiromycin is not effective.
• Some patients have been shown to have improvement in their clinical symptoms with the gastrointestinal hormone octreotide. The dosage is 300 to 500 mcg three times a day.
• Cryptosporidium is on the CDC recommended reporting list of infectious diseases; however, not all states in the United States mandate reporting Cryptosporidium.

• Since the oocysts can be shed in the stool for a long time after clinical resolution, it is not necessary to check follow-up convalescent stools. However, it is important to realize that asymptomatic patients can still transmit the infection to household and day care contacts.
• Requiring patients whose diarrhea has resolved to have a negative stool test for Cryptosporidium before reentry to day care has not been evaluated as an outbreak control measure. Repeated testing is expensive.

• Isolation of hospitalized patient
  • Contact precautions (i.e., gown and gloves for all patient contact) are recommended for the length of the hospital stay. If possible, a single bedroom would be optimal so that a bathroom does not need to be shared.
• Community prevention
  • Public water supplies should be adequately filtered in order to ensure oocyst removal.
  • Communities that do not use filtration systems are at increased risk for outbreaks, the most recent of which was the Milwaukee epidemic, where an estimated 400,000 people were affected.
  • Homeowners with well water should consider installing drinking water filtration systems.
  • Sources of drinking water should be protected from possible fecal contamination.
  • Garden hoses should not be used to provide drinking water.
  • All juices should be pasteurized. Cryptosporidum has been shown to survive in unpasteurized apple cider for up to 4 weeks.
  • Symptomatic patients should not be allowed to swim in public pools.
  • Good handwashing after contact with animals.
• Control measures
  • Hand washing especially after changing diapers.
  • Separation of diapering and food handling areas.
  • Disinfection of diapering areas after each use, frequent (at least twice daily) disinfection of toys, table tops, and high chairs during outbreaks is recommended.
  • Oocysts can survive for long periods and are resistant to many disinfectants such as: pine oil, cresylic acid, ethanol, n-propanol, isopropanol, lysol, phenol, iodophores, aldehydes, benzylkonium chloride, and quaternary ammonia compounds. Exposure of oocysts to 5.25% sodium hypochoride (full strength bleach) will destroy infectivity after 10 minutes. However, normally used concentrations of bleach have been shown to be poor disinfectants for Cryptosporidium. And 3% hydrogen peroxide is felt to be more effective and is recommended for outbreak control; 5% ammonia is also effective, however, it has a strong odor and if mixed accidentally with chlorine containing solutions (such as bleach) can produce hazardous chlorine gas.
  • Temporarily excluding or, if possible, cohorting symptomatic children. Since fecal shedding can be quite prolonged, it is generally recommended that once symptoms have resolved children should be allowed to return to their regular settings.
• During an outbreak, screening should be considered for children and caregivers who are in a household or in close contact with immunocompromised persons.
• Swimming pools found to be contaminated with Cryptosporidium require closing and hyperchlorination. The level of chlorination required to kill cryptosporidium oocysts is approximately 640 times greater than that required to kill Giardia cysts. Maintaining this level of chlorination is not feasible and, therefore, swimming in public pools places an immunocompromised patient at increased risk.

• Not considering the diagnosis in patients with acute diarrhea.
• Not sending the appropriate number of stool specimens to exclude the diagnosis.
• Assuming the microbiology lab will routinely test for C. parvum.
• Forgetting to test for other parasites if C. parvum is found in the stool.

Q: For whom should Cryptosporidiosis as a differential diagnosis be considered?
A: For anyone with acute onset of watery diarrhea with any of the mentioned risk factors.

Q: When is it safe for a child with Cryptosporidium to return to day care?
A: When the diarrhea has resolved.