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Last reviewed: 3 Nov 2023
Last updated: 09 Jul 2019



History and exam

Key diagnostic factors

  • diarrhea
More key diagnostic factors

Other diagnostic factors

  • abdominal pain
  • vomiting
  • loss of appetite
  • low-grade fever
  • loss of weight
  • right upper quadrant abdominal pain
  • jaundice
  • nasal discharge and facial pain
  • cough and dyspnea
Other diagnostic factors

Risk factors

  • contact with farm animals, especially calves and lambs
  • international travel
  • age: 3 years or younger
  • immune deficiency: T-cell-mediated
  • swimming and recreational water sports
  • drinking unfiltered water
  • toileting or changing diapers of young children
More risk factors

Diagnostic investigations

1st investigations to order

  • stool microscopy
  • Cryptosporidium antigen detection
More 1st investigations to order

Investigations to consider

  • ultrasound scan of the biliary tract
  • CT scan of the biliary tract
  • endoscopic retrograde cholangiopancreatography (ERCP)
  • polymerase chain reaction for Cryptosporidium DNA
  • polymerase chain reaction for Cryptosporidium species identification
More investigations to consider

Treatment algorithm






Rachel M. Chalmers, BSc, PhD

Consultant Clinical Scientist/Honorary Professor

Director of UK Cryptosporidium Reference Unit

Public Health Wales Microbiology

Singleton Hospital




RMC is a member of the following boards: WHO Water Quality and Health Technical Advisory Group; the UK Standards for Microbiology Investigations Bacteriology Working Group; Public Health England Water Advisory Group and Gastro-Intestinal Leads Group; Wales Microbiology Standing Specialist Advisory Group. RMC has received grant funding from EU FP7 project "Aquavalens" and EFSA partnering grant project IMPACT and has undertaken contract research from UK Water Industry Research. RMC has received payments for lectures and reimbursement for conference travel and subsistence. RMC is an author of a number of references cited in this topic.

Angharad P. Davies, MA, MBBCh, MRCP, FRCPath, PhD

Clinical Associate Professor

College of Medicine

Swansea University




APD is an author of a number of references cited in this topic.

Peer reviewers

Beth Kirkpatrick, MD

Assistant Professor

Infectious Diseases

University of Vermont College of Medicine




BK declares that she has no competing interests.

Yann Meunier, MD


Stanford Health Promotion Network

Stanford School of Medicine

Palo Alto



YM declares that he has no competing interests.

  • Cryptosporidiosis images
  • Differentials

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    • Chronic diarrhea
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  • Guidelines

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    • Guidelines for the prevention and treatment of opportunistic infections in HIV-exposed and HIV-infected children
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  • Patient leaflets

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    Diarrhea in children

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