ARS | Publication request: EFFECT OF HEAT AND COLD ON INFECTIVITY OF CRYPTOSPORIDIUM PARVUM

Submitted to: Society of Protozoologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 1996
Publication Date: N/A

Technical Abstract: Knowledge of temperatures affecting the infectivity of Cryptosporidium parvum (Cp) oocysts is vital to understanding the epidemiology and control of infections, as well as for storage of oocysts for research. In all studies, 1x10**5 oocysts were given by gastric intubation (GI) to neonatal BALB/c mice, ileum was fixed for histology 96 hr later, and infectivity was based on microscopic finding of Cp stages. Purified Cp oocysts suspended in d.H2O were stored for 1-168 hr at 5 deg C, -10 deg C, -15 deg C, -20 deg C, and -70 deg C, then raised to 21 deg C before GI. Oocysts stored as long as 168 hr at 5 deg C and -10 deg C, 24 hr at -15 deg C, and 5 hr at -20 deg C were infectious; all others lost infectivity. Oocysts in d.H2O heated in a thermocycler for 1 min to _>72.4 deg C for 1 min or _>64.2 deg C for 5 min lost infectivity. Oocysts in d.H2O and whole milk heated to 71.7 deg C for _>5 sec in a commercial-style pasteurizer lost infectivity. Because the finding of Cp oocysts in potable water has resulted in boil water alerts which are expensive, inconvenient, and even impossible in some commercial situations, and because some immunosuppressed persons must be vigilant to always exclude oocysts from their drinking water, these findings provide guidelines for alternative treatments.