A survey was conducted in the Czech Republic to determine whether serological responses to the 15/17-kDa and 27-kDa Cryptosporidium antigens had changed since the end of the communist era and if these responses were associated with drinking water sources. Sera from 301 blood donors residing in six areas served by various sources of drinking water were analysed by Western Blot (mini-immunoblots) to measure the IgG response. The intensity of response and percentage of persons with a strong response to the 27-kDa, but not the 15/17-kDa, antigen were higher than found 20 years earlier. A strong response to both the 15/17- and 27-kDa-antigens was higher than reported in other countries, and the probability of persons having a strong response was greater in areas with surface water sources than river-bank infiltration. Few cases of cryptosporidiosis were reported in spite of these high responses to Cryptosporidium antigens. These responses suggest a chronic low-level exposure from several sources that may be affording protection against symptoms and illness. Although strong serological responses were associated with surface water sources, drinking water is not likely to be the most important exposure for Cryptosporidium in the Czech Republic.

Department of Biostatistics National Institute of Public Health Šrobárova 49 48 100 00 Praha 10 Czech Republic

Department of Water Hygiene National Institute of Public Health Šrobárova 49 48 100 00 Praha 10 Czech Republic E mail

Grant and Project partners s r o Ústecká 218 13 184 00 Praha 8 Czech Republic

Gunther F Craun and Associates 14 Madison Place Staunton VA 24401 USA

Scientific Laboratory Division New Mexico Department of Health 1101 Camino de Salud NE Albuquerque NM 87102 USA

University of New Mexico 9814 Fostoria Rd NE Albuquerque NM 87111 USA

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