Inactivation of Cryptosporidium parvum oocysts in fresh apple cider by UV irradiation

Abstract

This study evaluated the efficacy of UV irradiation on the inactivation of Cryptosporidium parvum oocysts in fresh apple cider. Cider was inoculated with oocysts and exposed to 14.32 mJ of UV irradiation/cm(2). Oocyst viability was assessed with the gamma interferon gene knockout (GKO) mouse and infant BALB/cByJ mouse models. All GKO mice challenged with UV-treated cider demonstrated no morbidity or mortality, and infant BALB/c mice challenged with treated cider were negative for the presence of C. parvum. In contrast, the GKO mice challenged with non-UV-treated inoculated cider died and the parasite was detected in the ileums of all challenged infant mice. This study shows that UV irradiation can be used to inactivate C. parvum in fresh apple cider.

FIG. 1.

GKO mouse survival after challenge with UV-irradiated apple cider or untreated apple cider inoculated with C. parvum oocysts. Groups of six animals each were challenged by oral gavage with UV-irradiated apple cider containing 10³ oocysts (▵), 10⁴ oocysts (⋄), 10⁵ oocysts (□), or 10⁶ oocysts (○) or with untreated cider containing 10³ oocysts (•), 10⁴ oocysts (♦), 10⁵ oocysts (▪), or 10⁶ oocysts (▴). Control groups were challenged with uninoculated cider or 10⁵ oocysts in PBS (+).

FIG. 2.

Apple cider inoculums used as PCR controls, fecal specimens, and intestinal tissue were analyzed by PCR for the presence or absence of C. parvum. (A) Aliquots of untreated and UV-irradiated apple cider containing 10⁵ C. parvum oocysts/ml were spotted directly onto fluorescent treponemal antibody (FTA) filter disks and analyzed by PCR. Lanes a through f represent 1-, 3-, 5-, 10-, and 20-μl samples, respectively. (B) Fecal specimens from GKO mice inoculated at the indicated dosage with either untreated or UV-irradiated C. parvum-containing apple cider were analyzed by PCR for the presence of C. parvum. (C) Intestinal tissue isolated from GKO mice inoculated with either untreated C. parvum-containing apple cider (10³ oocysts) or UV-irradiated C. parvum-containing apple cider (10⁶) was analyzed by PCR for the presence of C. parvum. Lanes a through d represent 1, 5, 10, and 20 μl of tissue homogenate applied to FTA filter disks, respectively. Unmarked lanes contain 100-bp standards.