Viability of preserved Cryptosporidium baileyi oocysts

Abstract

The present study was undertaken to determine the viability and infectivity of oocysts of Cryptosporidium baileyi that had been stored from 1 to 40 months at 4 degrees C preserved in 2.5% potassium dichromate solution. Oocysts of C. baileyi were purified from the feces of experimentally infected chickens using discontinuous sucrose gradients. Subsequently, the purified oocysts were suspended in 2.5% potassium dichromate solution at a concentration of 1 x 10(7) organism/ml, and their viabilities were assessed by nucleic acid staining, histologic examination, and infectivity to 2-day-old chickens. All chickens inoculated with oocysts that had been stored for 1-18 months developed patent infections, while chickens infected with older oocysts remained uninfected. Between 5.8% and 82.2% of the oocysts, stored at 4 degrees C in 2.5% potassium dichromate solution, were found to be viable, as determined by nucleic acid staining. Parasite colonization in the bursa of Fabricius was detected in the microvillus border of bursal epithelium. The finding that C. baileyi oocysts remain infective to chickens for at least 18 months offers important time-saving advantages to investigators who frequently require large numbers of oocysts.

Identification and determination of the viability of Giardia lamblia cysts and Cryptosporidium parvum and Cryptosporidium hominis oocysts in human fecal and water supply samples by fluorescent in situ hybridization (FISH) and monoclonal antibodies

“…With FISH and FITC-conjugated MAbs, 9 (18%) out of 50 human feces parasitologically positive for G. lamblia and 3 (5%) out of 61 feces parasitologically positive for C. parvum and C. hominis presented viable and nonviable cysts and oocysts, respectively. A greater amount of nonviable (oo)cysts were detected in the oldest fecal samples, corroborating the results obtained in other studies (Jenkins et al 2003;Surl et al 2003). Viable Giardia spp.…”

Viability staining and animal infectivity of Cryptosporidium andersoni oocysts after long-term storage

“…Data represent mean ± SD of three independent replicates. *Significant difference between DW and PDS at P<0.05 genus Cryptosporidium as reported by Surl et al (2003). They described infectivity of C. baileyi for 2-day-old chicken after 18 months of storage at 4°C in PDS.…”

“…The difference in viability and infectivity of oocysts found in our experiment could be elucidated probably by loss of enzyme activity, although specific nucleic acid staining provided negative results (non-infective oocysts remained unstained like viable ones). C. andersoni oocysts in our experiment as well as those of C. baileyi (Surl et al 2003) lost infectivity for host after long-term storage, although the number of viable oocysts seemed to be high enough for successful infection. Other authors explained the infectivity of C. parvum oocysts stored at 4°C in DW for neonatal BALB/c mice similarly (Jenkins et al 2000) because they observed the correlation between detectable mRNA for C. parvum amyloglucosidase by RT-PCR and loss of infectivity.…”

“…It is important for epidemiology as well as for experimental research to determine the factors affecting the survival of cryptosporidium oocysts. The effects of different storage medium on the viability of cryptosporidium oocysts at a wide range of temperatures have been reported (Anderson 1985;Rhee and Park 1996;Jenkins et al 2003;Surl et al 2003). The infectivity of cryptosporidium oocysts can be tested using experimental model hosts or assays developed (cell culture) as an alternative to host infection studies (Slifko et al 1997).…”

Zinc PVA versus potassium dichromate for preservation of microsporidian spores of human origin

“…In modified PVA, zinc sulphate is incorporated instead of mercuric chloride to avoid the dangerous hazards of the latter (Garcia 2001). Another preservative is potassium dichromate solution which is frequently used for storage of viable coccidian spores for months (Dalton et al 2001;Surl et al 2003;Kvác et al 2007). …”