Epidemiologic Surveillance in Israel of Cryptosporidium, a Unique Waterborne Notifiable Pathogen, and Public Health Policy

Background: Cryptosporidium is a major threat to water supplies worldwide. Various biases and obstacles in case identification are recognized. In Israel, Cryptosporidiosis was included among notifiable diseases in 2001 to determine the burden of parasite-inflicted morbidity and to justify budgeting a central drinking water filtration plant. Objective: To summarize the epidemiologic features of 14 years of Cryptosporidium surveillance and to assess the effects of advanced water purification treatment on the burden of disease. Methods: From 2001 to 2014, a passive surveillance system was used. Cases were identified based on microscopic detection in stool samples. Confirmed cases were reported electronically to the Israeli Ministry of Health. Overall rates as well as age, gender, ethnicity and specific annual incidence were calculated per 100,000 population in five age groups: 0-4, 5-14, 15-44, 45-64, > 65 years. Results: A total of 522 Cryptosporidium cases were reported in all six public health districts. More cases were detected among Jews and among males, and mainly in young children, with a seasonal peak during summer. The Haifa sub-district reported 69% of the cases. Most were linked to an outbreak from the summer of 2008, which was attributed to recreational swimming pool activity. Cases decreased after installation of a central filtration plant in 2007. Conclusions: As drinking water in Israel is treated to maximal international standards, the rationale for further inclusion of Cryptosporidium among mandatory notifiable diseases should be reconsidered. Future surveillance efforts should focus on timely detection of outbreaks using molecular high-throughput testing.