Impact/Purpose:

1) Develop practical and inexpensive immunological methods to detect human exposure to Cryptosporidium.

2) Develop practical, specific, and inexpensive methods to detect C. parvum in water.

Description:

Research is undertaken to develop practical and rapid methods for isolation, identification, and quantification of waterborne pathogens. Research is also conducted to determine human exposure to these pathogens. Of immediate concern is Cryptosporidium for which such standardized and effective techniques are not yet available. Immunological methods may provide the sensitivity and specificity needed for these methods. Isolation and identification methods are needed before treatment and control procedures can be evaluated and regulatory decisions made. Conceptually, the approach taken in these studies will be as follows: the agent will be purified, and if necessary, its antigens analyzed by biochemical and immunochemical methods. Based on these results, the desired antigens will be isolated and characterized. Methods will be developed using these antigens.

Record Details:

Record Type:PROJECT

Start Date:01/01/1999

Projected Completion Date:09/01/2003

OMB Category:Other

Record ID: 15799

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Project Information:

Progress :We have detected, classified, and followed antibody responses against C. parvum in a population that experienced a waterborne cryptosporidiosis outbreak by ELISA and Western blot assay. High titer IgG, IgA and IgM combined, IgM only and IgG only anti-C. parvum antibodies were elevated during the outbreak and decreased 6 months after the outbreak as expected in the absence of outbreak conditions. Two years later after the outbreak when no new outbreak was reported, the strong positive IgM antibody level remained low similar to the level 6 months after the outbreak. Two years after the outbreak, the high titer IgG antibody increased to about twice the level during the outbreak. During this time, no new outbreak was reported. Based on the IgG response profile, the population probably was being re-exposed to the parasite or cross-reacting organism(s). The above findings generally typify that of the classical primary and secondary responses to an infection. During the outbreak, the IgM antibody level was elevated then decreased after the outbreak. The IgG antibody response was also elevated during the outbreak followed by a decrease after the outbreak. Upon re-exposure to the same infectious parasite, the IgM antibody level remained low whereas, the IgG response was enhanced to a level much greater than the primary response. By looking at the high titer antibody responses to C. parvum, enzyme-immunoassays can be useful in determining and monitoring disease outbreaks.

Western blot analyses of sonicated oocysts, cell walls, and sporozoites yielded different antigenic profiles using strong positive sera. Different individuals appear to qualitatively and quantitatively respond differently to the oocysts, cell walls, and sporozoites. Different classes of Igs detect different C. parvum antigens at varying intensities.

Relevance :To date, there is no rapid, reliable, practical, and specific method to detect C. parvum infection. A suitable test is needed for a large-scale epidemiological study of the significance of drinking water in the transmission of cryptosporidiosis. It is expected that the method developed can also be applied to screen exposure to other potential pathogens of waterborne outbreaks.

These tasks meet the need of the Agency's strategic goal of clean and safe water, ORD's strategic goal of "Discovery and innovation revolutionize environmental decision-making," and NERL's long term goal to provide improved exposure assessment methods and models and information needed for guidance on exposure evaluation.

M/DBP Research Plan Relationship: Topic area Ex.M.13a.

Clients :Office of Ground Water and Drinking Water (Dr. Paul Berger)

Research Component :M/DBP (MICROBIAL)

Risk Paradigm :EXPOSURE

Project IDs:

ID Code :EX.M.13a

Project type :ORD-DW Plan

ID Code :376

Project type :OMIS