Epidemiology & Risk Factors
Pathogen : Cryptosporidium parvum or C. hominis (intracellular protozoa).Transmission : Fecal-oral ingestion of chlorine-resistant oocysts via contaminated water (swimming pools, municipal supply), daycare exposure, or animal contact. c Risk Factors :
Immunocompromised state: HIV/AIDS w/ CD4 < 100/mm³ , solid organ transplant, congenital T-cell immunodeficiencies.
Immunocompetent: Travelers, pool users, daycare workers. c
Clinical Features
Immunocompetent :
Self-limiting profuse, watery, non-bloody diarrhea .
Crampy abdominal pain, low-grade fever, nausea, anorexia (resolves in 1–2 weeks).
Immunocompromised (HIV w/ CD4 < 100/mm³) :
Chronic, intractable, severe secretory diarrhea (> 2–3 L/day).
Malabsorption, profound weight loss, severe electrolyte wasting, dehydration.
Diagnosis
Initial/Key Test : Stool examination with modified acid-fast stain revealing pink/red oocysts (4–6 µm).Confirmatory/High-Sensitivity Tests :
Stool PCR assay (multiplex GI panel).Stool immunoassay (EIA/ELISA) for Cryptosporidium antigen.
Biopsy (Rarely needed) : Intracellular organisms lining the brush border of intestinal epithelial cells.
Differential Diagnostics
Cystoisospora belli larger, oval-shaped oocysts on modified acid-fast stain; treat w/ TMP-SMX .Microsporidia non-acid-fast (requires chromotrope 2R/calcofluor white stain); treat w/ Albendazole .Giardia lamblia pear-shaped trophozoites with 2 nuclei; presents w/ severe bloating, foul-smelling flatus, steatorrhea; treat w/ Metronidazole .CMV Colitis : Diff by bloody diarrhea , CD4 < 50, mucosal ulceration, colonoscopy biopsy w/ intranuclear inclusion bodies (“owl’s eye”) ; treat w/ Ganciclovir .Mycobacterium avium complex (MAC) : Diff by CD4 < 50, high fevers, night sweats , hepatosplenomegaly, watery diarrhea; treat w/ Azithromycin + Ethambutol .
Management
Immunocompetent :
Supportive : Fluid and electrolyte replacement.Persistent/Severe : Nitazoxanide (orally for 3 days).
Immunocompromised (HIV/AIDS) :
Primary/Most Effective Tx : Antiretroviral Therapy (ART) to restore immune function (CD4 > 100/mm³ drives clearance).Symptomatic/Adjunctive : Nitazoxanide (decreased efficacy without immune reconstitution).Supportive : Aggressive IV hydration, antidiarrheals (e.g., loperamide, octreotide if refractory).
Complications
Severe hypovolemic shock & acute kidney injury (AKI) from dehydration.
AIDS Cholangiopathy : Acquired sclerosing cholangitis or acalculous cholecystitis (presents w/ RUQ pain, ↑ ALP).Failure to thrive and severe malnutrition/wasting in chronic cases.