PATHOGENS

• Cryptosporidium is an intracellular protozoan parasite. C. hominis, C. parvum, and C. meleagridis most commonly infect humans.
• Sporulated oocysts measure 4.2 to 5.4 micrometers in diameter.[11] Once ingested, they excyst and attach to intestinal epithelium. Trophozoites mature to meronts, which release merozoites leading to zygote formation. To complete the life cycle, oocysts are released through stool into the environment.
• In immunocompromised individuals, parasites develop intracellularly throughout the epithelium of the small intestine, biliary tree, and pancreatic ducts. Infection causes loss of villi, crypt hyperplasia, and reduction in brush border enzyme activity.
• Environmental oocysts are infectious when shed, can survive for at least 6 months in moist environment, and are resistant to chlorination. Oocysts are sensitive to dessication, hydrogen peroxide, ozone, and UV radiation.
  • Most outbreaks are due to contaminated water supply (Milwaukee, WI, 1993) or recreational water source.
  • Cryptosporidium’s resistance to chlorine disinfection enables food- and waterborne transmission. Enhanced water treatment strategies may combine filtration with UV light or ozone with chlorination.[7]
• A fecal-oral route of transmission via person-to-person among family members or among sexual contacts tends to occur because the infectious dose is as few as 10 oocysts.
  
  • Zoonotic and foodborne transmission may occur through the ingestion of contaminated raw oysters or raw milk.[3]