Genotype of Cryptosporidium parvum that Caused an Outbreak of Cryptosporidiosis in Hokkaido in 2002

An outbreak of cryptosporidiosis occurred in Sapporo on April in 2002. One hundred-seventy students, who went on a study tour in Iburi district as a group of 300 vocational school students and stayed at a hotel from April 8 to April 10, suffered from the protozoan disease characterizing diarrhea. Cryptosporidium oocysts were microscopically detected in six out of thirteen fecal specimens collected from the students. The existence of Cryptosporidium oocysts in the microscopically-positive samples was immunologically confirmed by immunofluorescence using monoclonmal antibody to Cryptosporidium parvum oocyst wall protein. Genetic analysis was also conducted by PCR (using the polythreonine gene-targeting primers) followed by RFLP (using Rsa I). It clearly showed that all the six isolates was genotype 1 of C. parvum (so-called human type). Administrative inspections were made for 350 employees who worked at the hotel when the vocational school students stayed. Out of them, 28 hotel employees were found to be Cryptosporidium-positive in microscopic, immunologic and/or genetic examinations. Analysis of the PCR products revealed that there was no difference in nucleotide sequence between C. parvum isolates from the vocational school students and those from the hotel employees. Epidemiological investigation found another group, which included patients who had diarrhea. This group stayed at the same hotel from April 8 to April 10. The group comprised of 153 university students in Ebetsu and eight students out of them developed diarrhea and its related symptoms after their return from the tour. In three out of five fecal specimens, which were collected from students with diarrhea, Cryptosporidium oocysts were also detected. One of the three fecal specimens was PCR-positive and the following RFLP analysis clearly indicated that the oocysts were genotype 1 of C. parvum