Quantitative Evaluation of Infectivity Change of Cryptosporidium parvum after Gamma Irradiation

Abstract

Cryptosporidium parvum is an obligate intracellular protozoan that infects a wide range of vertebrates, including humans and animals [1]. Most infections are acquired from water or food contaminated with infectious oocysts [2,3]. Cryptosporidium has been a threat to the water industry and public health since 1980 when AIDS became a public health issue, and its low infection dose and high resistance to various disinfectants facilitate its high infection rate [4][5][6].Gamma irradiation has been used to prevent some food-borne infections derived from parasites and to produce vaccines for parasitic infections [7][8][9][10]. We have previously shown that gamma irradiation at 50 kGy is necessary for a complete elimination of C. parvum oocyst excretion in vivo [11], which is the highest reported resistance to irradiation among parasites. In the present study, we investigated the reduction of the infectivity of C. parvum by gamma irradiation and the repair of the infectivity using absolute quantitative real-time PCR (qPCR). As it has been already known that in vitro infectivity of C. parvum using human ileocecal anenocarcinoma cell line (HCT-8) could be a useful substitute for animal infectivity study, and CP2 gene is a useful viability marker for quantitation of C. parvum [12,13], we evaluated infectivity change and repair of C. parvum after gamma irradiation quantitatively using an in vitro system. Several biological characteristics of non-irradiated C. parvum were also evaluated quantitatively, including changes in viability and in vitro infectivity during 12 months of storage, and the time point when the number of parasites was maximal in a cell culture system. MATERIALS AND METHODS C. parvum oocyst preparation and gamma irradiationThe oocysts of C. parvum (KKU isolate) maintained in specific pathogen-free C57BL female mice were purified according to the method of previous papers [14,15]. The purified oocysts were surface sterilized by placing them in 10% sodium hypochlorite solution for 10 min, and they were stored for less than 2 wk at 4℃ before the experiment. As we found that C. parvum sporozoites maintained their infectivity up to 13 days in this study, we irradiated sporozoites directly and used them for the viability and in vitro infectivity studies. For excystation, oocysts were incubated in acidified Hanks' balanced salt solution (pH 2.75) for 10 min at 37℃ in a shaking incubator, followed by incubation in 4 mM sodium taurocholate (Sigma, St. Louis, Missouri, USA) in phosphate-buffered saline (PBS, pH 7.4) at 37℃ for 15 min [16]. A 1.5-ml microcentrifuge tube containing 8 × 10 7 of C. parvum sporozoites with 1 ml of Dulbecco's modified Eagle's medium (DMEM) (Sigma) was immersed in a 50-ml tube filled with distilled water, both to obtain the backscattered ray and to Quantitative Evaluation of Infectivity Change of Cryptosporidium parvum after Gamma IrradiationKorean J Parasitol. Vol. 47, No. 1: 7-11, March 2009 DOI: 10.3347/kjp.2009 Medicine, Chungbuk National University, Korea Abstract: Cryptosporidium...

Immunization of V-line rabbits against intestinal coccidiosis by using attenuated Eimeria oocysts.

“…Immunization of rabbits against eimeriosis by different attenuated sporulated Eimeria oocysts on experimentally infected rabbits with this attenuated oocysts showed a pre-patent period 5-6 days. Our result close ratio is consistent with that of Akpo et al(2012) The current result showed that the degree of clinical symptoms was decreased in the attenuated groups than that of the control group, this result was in agreement with that of Lee et al(2009) who recorded that Cryptosporidium parvum oocysts where subjected to gamma irradiation at various doses (1,5,10,and 25 kGy) showed reduction of the infectivity and repair of the infectivity after irradiation and Ramadan et al (2018)who reported that immunization of lambs by using one hour UV irradiated Eimeria oocysts showed no signs of recumbency, fever and off food ,only lambs showed soft feces at 13 th PI and, while our result were disagreed with Ramamoorthy et al(2006) who evaluated that vaccination of female mice with two intraperitoneal inoculation of 1x10 6 of 528 Gy of gamma irradiated Neospora caninum tachyzoites and challenged intraperitoneally with 1x10 7 N. caninum tachyzoites. All vaccinated mice remained healthy and showed no obvious signs of neosporosis.…”

Evaluation of the effect of radioactive cobalt-60 and ultraviolet rays on Giardia lamblia infectivity to mice

“…Since the early nineties, cobalt-60, a type of gamma radiation, has been used on food to control infectivity of several parasites as Paragonimus westermani [13] , Metagonimus yokogawai [14] , Eimeria tenella [15] , Toxoplasma gondii [16] , Angiostrongylus cantonensis [17] , Taenia solium [18] , Clonorchis sinensis [19] , Cryptosporidium parvum [20] , Ascaris lumbricoides [21] , Trypanosoma cruzi [22] and Echinococcus granulosus [23] . UV irradiation usage for the disinfection of drinking water was first applied in 1910 in Marseille.…”

Ultrastructural Changes inCryptosporidium parvumOocysts by Gamma Irradiation

“…This is the highest reported resistance to irradiation among parasites. In a recent report, the infectivity of C. parvum oocysts in HCT-8 cells was reduced under 3 log 10 by 10 kGy irradiation [ 6 ]. Since the dose of C. parvum required for infection is known to be quite low [ 7 ], even 0.1% of oocysts that maintain infectivity still pose a threat to the host.…”