cryptosporidiosis

Introduction

First recognized as an opportunistic infection in patients with AIDS.

Etiology

• Cryptosporidium hominis
• Cryptosporidium parvum

Epidemiology

• highly infectious
  • human to human fecal-oral transmission
• most often seen in AIDS patients (HIV1 infection)
  • estimated world-wide prevalence in HIV1-infected patients is 9%
• outbreaks occur in immunocompetent patients
• in 1993 over 400,000 people in Milwaukee, Wisconsin developed diarrhea after contamination of the public water supply with Cryptosporidium
  • contamination of the water supply resulted from farm runoff after heavy rains
• resistant to chlorine
• not effectively removed by many water filtration systems
• common in developing nations
• outbreaks linked to recreational water facilities (pools, water playgrounds)
• oubreaks increased by 13% per year from 2009-2017

Pathology

• parasites develop in brush border epithelium of the small intestine & colon
• occasional spread to gall bladder, pancreas & respiratory tract
• intensity of clinical disease parallels burden of organisms
• bowel mucosa may be normal or show flattened or denuded villi or crypt hyperplasia
• malabsorption
  • vitamin B12
  • fat

Clinical manifestations

• often asymptomatic is health persons
• acute, self-limited diarrhea
  • incubation period is about 8 days
  • illness lasts 9-23 days
  • fever, malaise, abdominal cramps, watery diarrhea

Laboratory

• diagnosis is made by microscopy for oocysts in feces
  • oocysts measure 4 by 6 um in diameter
  • routine stool examination for ova & parasites does not detect Cryptosporidium
  • concentration methods work well
  • formalin-ethyl acetate
  • Sheather's sugar floatation
  • modified acid fast stains
    • auramine-O
    • modified Kinyoun method most widely used
    • positive & negative controls must be run with each specimen
  • direct immunofluorescent antibody testing
  • Cryptosporidium antigen in stool (EIA)
• Cryptosporidium identified in intestine
  • gastrointestinal endoscopy with small bowel biopsy may be necessary to establish the diagnosis if oocysts are not recovered in feces
• Cryptosporidium DNA in stool
• Cryptosporidium culture in stool
• HIV1 serology if refractory symptoms

* image of oocysts

Complications

• in AIDS patients, Cryptosporidium may cause secretory chronic diarrhea, dehydration, weight loss, & death

Management

• generally self-limited
• no effective therapy
• supportive therapy
  • IV fluids
  • anti-diarrheal agents
  • contact precautions, hand-washing
• HIV/AIDS patients
  • highly-active antiretroviral therapy (HAART)
  • paromomycin (aminosidine)
    • 500 to 750 mg PO TID
    • 1 g every 12 hours for 1 month followed by 0.5 g every 12 hours
    • relpase may occur with cessation of therapy
• nitazoxanide may facilitate resolution of symptoms
  • efficacy in patients with AIDS unproven
    • screening for HIV1 if refractory symptoms
  • may be useful in AIDS patients with CD4 counts < 100/uL
• biliary obstruction may require papillotomy or T-tube placement

More general terms

• coccidiosis
• parasitic gastroenteritis

Additional terms

• Cryptosporidium parvum

Patient information

cryptosporisiosis patient information