Use of aerobic spores as a surrogate for cryptosporidium oocysts in drinking water and supplies

Authors: Headd, Brendan; Bradford, Scott

Submitted to: Water Research
Publication Type: Review Article
Publication Acceptance Date: 12/13/2015
Publication Date: 12/17/2015
Citation: Headd, B.J., Bradford, S.A. 2015. Use of aerobic spores as a surrogate for cryptosporidium oocysts in drinking water and supplies. Water Research. 90:185-202. doi: 10.1016/j.watres.2015.12.024.

Interpretive Summary: Regulations in the United States to protect groundwater supplies from disease causing microorganisms have focused on the removal of the pathogen Cryptosporidium. However, accurate determination of pathogen risk in groundwater is hampered by inaccuracies in methods to detect the low, sporadic concentrations of Cryptosporidium in the environment. This manuscript reviews and synthesizes the literature to determine whether aerobic spores are a suitable surrogate for Cryptosporidium oocysts in groundwater. Results indicate that aerobic spores are a promising conservative surrogate for Cryptosporidium because of similarities in biology, prolonged survival, ease of detection, and high prevalence in the environment. However, additional research is needed to compare the surface properties, interactions, and migration potential of spores and Cryptosporidium in aquifers. This information will be of interest to government regulators, public water utilities, and scientists who are concerned with assessing the risks for pathogens in drinking water supplies.

Technical Abstract: Waterborne illnesses are a growing concern among health agencies worldwide and regulatory efforts to prevent microbial contamination of water supplies are constantly evolving to stay ahead of the threat. The United States Environmental Protection Agency has established several rules to combat the contamination of water supplies by Cryptosporidium oocysts, however, the detection and study of Cryptosporidium oocysts is hampered by methodological and financial constraints. As a result, numerous surrogates for Cryptosporidium oocysts have been proposed by the scientific community and efforts are underway to evaluate many of the proposed surrogates. The purpose of this review is to evaluate the suitability of aerobic bacterial spores to serve as a surrogate for Cryptosporidium oocysts in identifying contaminated drinking waters. To accomplish this we present a comparison of the biology and life cycles of aerobic spores and oocysts and compare their physical properties. An analysis of their surface properties is presented along with a review of the literature in regards to the transport, survival, and prevalence of aerobic spores and oocysts in the environment. Aerobic spores and oocysts share many commonalities with regard to biology and survivability, and the environmental prevalence and ease of detection make aerobic spores a good candidate surrogate for Cryptosporidium oocysts in surface and groundwater. However, the long-term transport and release of aerobic spores still needs to be further studied, and compared with available oocyst information. In addition, the surface properties and environmental interactions of spores are known to be highly dependent on the spore taxa and purification procedures, and additional research is needed to address these issues in the context of transport.