By Garry Palmateer, GAP EnviroMicrobial Services Inc.
The protozoan parasite Cryptosporidium parvum has become a major concern to the drinking water industry and public health officials around the world. The large outbreak in Sydney, Australia is an example of how Cryptosporidium can challenge experienced operators of current water treatment systems.
As consulting microbiologists on environmental issues, concerns arise weekly as to the many aspects of Cryptosporidium that affect potable water, recreational water, livestock runoff and effluents of water pollution control plants. GAP EnviroMicrobial Services are presently involved in studies investigating new technology in the disinfection of potable water using Cryptosporidium parvum as the test microorganism. The common component to all the studies is to determine the viability and infectivity of treated water containing live oocysts of Cryptosporidia.
Until recently, health officials estimating the health risk of Cryptosporidium in potable or recreational waters and manufacturers of disinfection technologies of water and sewage have had to rely on viability and infectivity data based on animal infection assays. This method is extremely costly, sometimes inconsistent and time-consuming, when the information required is immediate, but unavailable for up to three weeks.
A new method of demonstrating viability and infectivity of Cryptosporidium has been developed and tested against the mouse infectivity assay which is currently being used by the US CDC and the pharmaceutical industry. The new method, which involves the growth of human colon tissue (HCT-8 cells) has been shown to be on par with the mouse model studies and superior to the vital dye and excystation methods, which were the methods of previous researchers investigating inactivation of Cryptosporidium.
Cell culture technology has been developed into a tool that can now be used to study C. parvum in an environment most similar to in-vivo without using animals. Treated oocysts are inoculated into the HCT-8 cells and allowed to infect the host cells for up to 48 hours, and then fixed and labeled with a fluorescent antibody that binds to the developmental lifestages of C. parvum. The samples can then be observed, using epiluorescent microscopy, and the concentration of infectious C. parvum can be determined in 96 hours.
This new technology is very useful to consultants in the water treatment industry and public health officials, as well as manufacturers of new disinfection practices.