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🧫 About
Cryptosporidiosis is an opportunistic protozoal infection caused by Cryptosporidium parvum or C. hominis.
It primarily affects the small intestine, causing profuse watery diarrhoea.
Self-limiting (1–2 weeks) in immunocompetent hosts; chronic, severe, and potentially life-threatening in advanced HIV (CD4 <100 cells/µL).
🦠 Aetiology
- Transmission: faecal-oral via oocyst-contaminated water/food, person-to-person, or animal contact.
- Oocysts invade small-bowel epithelium → malabsorption/secretion; resistant to chlorine; biliary tract involvement (sclerosing cholangitis) in chronic HIV cases.
🧍♂️ Clinical Features
- Immunocompetent: Acute watery diarrhoea ± abdominal cramps, low-grade fever; resolves spontaneously.
- Immunocompromised (esp. HIV CD4 <100): Chronic profuse watery diarrhoea (>2 L/day), severe dehydration, weight loss, malnutrition, electrolyte imbalance; biliary symptoms (pain, cholangitis) in ~10–15%.
🔍 Differentials
- In HIV: Isospora belli, Microsporidia, Giardia, CMV colitis, HIV enteropathy, Mycobacterium avium complex.
- Non-infective: malabsorption syndromes, coeliac, pancreatic insufficiency.
🧪 Investigations
- Bloods: FBC (anaemia), U&E (dehydration/electrolytes), LFTs (biliary involvement).
- Stool: Microscopy (fresh/unconcentrated; modified acid-fast/Kinyoun stain – oocysts red); repeat samples (intermittent shedding); PCR/antigen detection for higher sensitivity/speciation (Grade 1B).
- Endoscopy/biopsy: Small-bowel biopsy if stool negative (oocysts on brush border).
💊 Management (BHIVA 2024 GI OI Compliant)
- Supportive: Aggressive oral/IV rehydration, electrolyte replacement, antimotility agents cautiously (risk of ileus in severe cases).
- Immune restoration: Optimise/effective cART (first-line; Grade 1C) → resolution in most with CD4 recovery >100 cells/µL.
- Antiparasitic: Nitazoxanide 500 mg BD (with food) for 3–14 days may shorten duration in mild/moderate immunosuppression (Grade 2B); limited/no benefit in severe immunodeficiency (CD4 <50–100).
- Prevention: Strict food/water hygiene (boil/filter water if high-risk); hand hygiene; avoid swimming during outbreaks.
📚 References (Current as of March 2026)
- BHIVA guidelines for the management of opportunistic infections: Gastrointestinal infections (2024 update). Full PDF.
- UK Health Security Agency (UKHSA). Cryptosporidium: public advice (last updated 1 November 2023). Link.
- Panel on Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents with HIV. Cryptosporidiosis (updated January 2025). NIH Clinicalinfo.
🕓 Revision History
- Last updated: March 2026 (aligned with BHIVA GI OI 2024; UKHSA 2023; NIH 2025 update).
