Cryptosporidium and giardia

Reducing human parasitic infection by breaking the cycle of transmission of parasites transmitted by the faeco-oral route has been one of the most significant interventions in public health medicine and, embodied at its most practical level, this has been the role of the sanitary engineer. In the last 30 years, there has been increasing epidemiological evidence linking two protozoan parasites of the intestinal tract of humans and other hosts with frequent outbreaks of waterborne disease. The parasites, Giardia duodenalis and Cryptosporidium parvum are the two most commonly reported parasites of human beings world-wide. Infectious organisms, present in contaminated potable water, have the potential to infect large numbers of people from one contamination event, and these two protozoan parasites have been responsible for over 140 outbreaks of waterborne disease affecting over 450 000 individuals. The transmissive stages (cysts of Giardia duodenalis and oocysts of Cryptosporidium parvum (oo)cysts) are frequent inhabitants of raw water sources used for the abstraction of potable water and their importance is heightened because, coupled to their low infectious doses (10-1000 organisms), conventional water treatment processes, including chemical disinfection, cannot guarantee their removal or destruction completely. Furthermore, due to their chlorine insensitivity, the coliform stan- dard cannot be relied upon as an indicator of either the presence or viability of Giardia cysts and Cryptosporidium oocysts. For these reasons, robust, sensitive and specific methods are required for the recovery and identification of (oo)cysts in water concentrates