title: Comparison of viability and infectivity of Cryptosporidium parvum oocysts stored in potassium dichromate solution and chlorinated tap water.
abstract: The present study was undertaken to compare the viability and infectivity of Cryptosporidium parvum oocysts that had been stored for 1, 4, 7, 10, 13, 16, 20, 25 and 30 months at 4 degrees C in 2.5% potassium dichromate (Cr) or chlorinated tap water, respectively. An excystation protocol was performed in vitro to evaluate viability. One hundred and eighty female BABL/c mice were used to evaluate the infectivity of oocysts by investigating the prepatent period of C. parvum infection, the quantity of oocysts excreted, and the number of parasites that colonized the villi of the ileum. The results showed that C. parvum oocysts preserved in Cr for 1-16 months or in water for 1-13 months were capable of excystation in vitro and infection of mice. The excystation rates of oocysts and the prepatent periods in mice infected by oocysts stored in Cr and water were not significantly different (p>0.05), and there was a strong correlation between prepatent period and duration of oocyst storage (Cr: R2=0.92; water: R2=0.98). There were no significant differences in oocyst shedding from feces or parasitism of the terminal ilea of mice by Cryptosporidia between the two storage media (p>0.05). In conclusion, C. parvum oocysts may be stored at 4 degrees C in water instead of Cr for the purposes of laboratory research. However, the presence of viable C. parvum oocysts in water is a severe challenge to the drinking water treatment industry.
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, Jiangsu Province, China.
authors.forename: Fu
authors.initials: F
authors.lastname: Chen
authors.forename: Kehe
authors.initials: K
authors.lastname: Huang
authors.forename: Shunyi
authors.initials: S
authors.lastname: Qin
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Zhao
authors.forename: Cuiling
authors.initials: C
authors.lastname: Pan
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects*; D002713:Chlorine / Q000737:chemistry / Q000494:pharmacology*; D016785:Cryptosporidium parvum / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D005243:Feces / Q000469:parasitology; D051379:Mice; D008807:Mice, Inbred BALB C; D033661:Oocysts / Q000187:drug effects* / Q000502:physiology*; D011192:Potassium Dichromate / Q000494:pharmacology*; D011309:Preservation, Biological; D012996:Solutions; D013048:Specimen Handling; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D012996:Solutions; D014867:Water; D002713:Chlorine; D011192:Potassium Dichromate