Survival, concentration, and non-microscopic detection of infectious Cryptosporidium in environmental waters.

摘要

The enteric protozoan parasite, Cryptosporidium parvum, causes waterborne disease outbreaks. In order to develop reliable occurrence data for quantitative risk assessments and risk management systems, it is important to determine the concentrations of infectious Cryptosporidium in environmental reservoirs and to characterize its survival in environmental waters.; This study determined the rates of survival of Cryptosporidium parvum oocysts in different environmental waters and under different environmental conditions. A simple, reliable, and robust ultrafiltration method was developed for concentrating and purifying Cryptosporidium oocysts from environmental waters, including high turbidity stream and low turbidity reservoir water samples. This method was compared to the candidate concentration and detection method currently approved for use by the U.S. EPA for recovery efficiency in paired tests with reagent and environmental water samples. In addition, a non-microscopic, quantitative method for detection of infectious Cryptosporidium was developed that is reliable, robust, and compatible with the concentration and detection methods now used to recover Cryptosporidium from water.; It was found that Cryptosporidium survives in environmental waters for long periods of time (weeks to months) at colder temperatures. Cryptosporidium survives less well in estuarine waters than in fresh waters. Cryptosporidium can be concentrated and detected by the current U.S. EPA Method 1622 in both reagent and environmental waters of varying quality, but the developed ultrafiltration method yields higher and more reliable recoveries for Cryptosporidium in environmental waters. Variability in recoveries was observed for each method tested that was attributed to matrix effects associated with the different environmental waters. An innovative non-microscopic method was developed for detection of infectious Cryptosporidium by tissue culture infectivity coupled with visualization of infectious foci by a chemiluminescent detection system. This method has proven to be reliable and applicable to Cryptosporidium oocysts recovered from water samples. The methods developed in this study can be used for the development of more reliable and quantitative occurrence data that will help management agencies protect the public from waterborne Cryptosporidium in the future.