MICROBIOLOGY

• Giardia lamblia, also G. duodenalis or G. intestinalis, is an anaerobic, flagellated, binucleate protozoan parasite that infects mammals.[4]
• It is the most common protozoal pathogen worldwide.[5]
  • G. lamblia is found in the surface water of northeastern and northwestern mountainous areas of U.S. and the Rocky Mountains.
  • Outbreaks occur in private residences, child care facilities, urban areas, and areas of over-crowding.[6]
• Its two-stage life cycle includes trophozoites and cysts. Ingestion of cysts is followed by excystation. Each cysts releases 2 trophozoites, which multiply and attach to the small bowel mucosa.
  • The infectious dose is small, less than 10 cysts, and cysts can be infectious when passed in the stool or soon thereafter.[3]
• Fecal-oral transmission occurs via contaminated food, person-to-person, sexual transmission, and waterborne outbreaks.
  • Due to the moderate chlorine tolerance of G. lamblia, drinking water, recreational water, and swimming pools contaminated with human feces can serve as reservoirs.
  • Because organisms can be transmitted via sexual contact, the CDC recommends abstinence from sexual activity for 2 weeks after diarrhea resolves.[6]