- 18S rRNA
- Cryptosporidium parvum
- nucleic acid extraction
Cryptosporidium is a protozoan parasite distributed worldwide. It is excreted in the feces of infected humans or animals and is the causative agent of cryptosporidiosis, whose symptoms include watery diarrhea, vomiting, and fever. While Cryptosporidium parvum and C. hominis are the primary species known to infect humans, recent studies suggest that C. cervine, C. felis, and C. meleagridis may also cause diarrhea in humans (Carey et al. 2004). The oocysts of Cryptosporidium spp. are shed in the feces and may then enter sewage treatment facilities via wastewater or persist in the environment. A previous study has demonstrated that some sewage treatments are not efficient enough to eliminate all the oocysts prior to water discharge (Bonadonna et al. 2002), which can lead to outbreaks of cryptosporidiosis. The largest outbreak of watery diarrhea was recorded in Milwaukee, WI, USA, in 1993 and was caused by Cryptosporidium oocysts that were not removed by the filtration system of one of the city's water treatment plants. Over 400,000 residents in the Milwaukee area presented watery diarrhea, abdominal cramps, fever, and vomiting symptoms (Mac Kenzie et al. 1994). Cryptosporidium oocysts present a robust wall resistant to several environmental factors as well as to many of the processes and substances normally used for water disinfection. The robust nature of the oocyst wall requires more stringent treatments for disruption (Carey et al. 2004). Thus, early detection of oocysts in untreated water sources is essential to ensure efficient quality control for drinking water.
Cryptosporidium oocysts in water and fecal samples have been generally purified with antibody magnetic beads or sucrose density-gradient centrifugation for Cryptosporidium testing (Simmons et al. 2001; Wohlsen et al. 2004). Then, the purified oocysts are identified by microscopy with fluorescent staining or genetic testing. Recently, the performance of real-time polymerase chain reaction (PCR) …