An improved in vitro infection model for viability testing of Cryptosporidium parvum oocysts

Nanoparticle Lysis of Cryptosporidium Oocysts

The extraction of DNA from Cryptosporidium oocysts is challenging due to the robust oocyst wall. Nanoparticles have been applied to disinfect Cryptosporidium oocysts; here, we demonstrate the utilisation of nanoparticles to disrupt the oocyst wall to enable sporozoite lysis and detection via PCR. Both silver and zinc oxide nanoparticles are investigated under different conditions and compared to existing techniques. Zinc oxide nanoparticles are shown to be as effective as freeze-thaw methods, suggesting that a nanoparticle lysis approach offers a viable alternative to existing methods.

Cryptosporidium parvum-induced neutrophil extracellular traps in neonatal calves is a stage-independent process

Introduction

Infections with the apicomplexan obligate intracellular parasite Cryptosporidium parvum lead to cryptosporidiosis-a worldwide zoonotic infection. C. parvum is one of the most common diarrheal pathogens in young calves, which are the main reservoir of the pathogen. Cryptosporidiosis leads to severe economic losses in the calf industry and being a major contributor to diarrhea morbidity and mortality in children. Polymorphonuclear neutrophils (PMN) are part of the innate immune system. Their effector mechanisms directed against invasive parasites include phagocytosis, production of antimicrobial molecules as well as the formation of so-called neutrophil extracellular traps (NETs). Like other leukocytes of the innate immune system, PMN are thus able to release chromatin fibers enriched with antimicrobial granular molecules extracellularly thereby immobilizing and partially killing invasive bacteria, viruses, fungi and parasites.

Methods

In vitro interactions of neonatal bovine PMN and C. parvum-oocysts and sporozoites were illustrated microscopically via scanning electron microscopy- and live cell imaging 3D holotomographic microscopy analyses. C. parvum-triggered NETosis was quantified via extracellular DNA measurements as well as verified via detection of NET-typical molecules [histones, neutrophil elastase (NE)] through immunofluorescence microscopy analysis. To verify the role of ATP in neonatal-derived NETosis, inhibition experiments were performed with NF449 (purinergic receptor antagonist with high specificity to P2X1 receptor).

Results and discussion

Using immunofluorescence- and SEM-based analyses, we demonstrate here for the first time that neonate bovine PMN are capable of forming NETs against C. parvum-sporozoites and oocysts, thus as a stage-independent cell death process. Our data further showed that C. parvum strongly induces suicidal neonatal NETosis in a P2X1-dependent manner, suggesting anti-cryptosporidial effects not only through firm sporozoite ensnarement and hampered sporozoite excystation, but also via direct exposure to NETs-associated toxic components.

MCT-Dependent Cryptosporidium parvum-Induced Bovine Monocyte Extracellular Traps (METs) under Physioxia

The apicomplexan protozoan parasite Cryptosporidium parvum is responsible for cryptosporidiosis, which is a zoonotic intestinal illness that affects newborn cattle, wild animals, and people all over the world. Mammalian monocytes are bone marrow-derived myeloid leukocytes with important defense effector functions in early host innate immunity due to their ATP purinergic-, CD14- and CD16-receptors, adhesion, migration and phagocytosis capacities, inflammatory, and anti-parasitic properties. The formation of monocyte extracellular traps (METs) has recently been reported as an additional effector mechanism against apicomplexan parasites. Nonetheless, nothing is known in the literature on METs extrusion neither towards C. parvum-oocysts nor sporozoites. Herein, ATP purinergic receptor P2X1, glycolysis, Notch signaling, and lactate monocarboxylate transporters (MCT) were investigated in C. parvum-exposed bovine monocytes under intestinal physioxia (5% O₂) and hyperoxia (21% O₂; most commonly used hyperoxic laboratory conditions). C. parvum-triggered suicidal METs were confirmed by complete rupture of exposed monocytes, co-localization of extracellular DNA with myeloperoxidase (MPO) and histones (H1-H4) via immunofluorescence- and confocal microscopy analyses. C. parvum-induced suicidal METs resulted not only in oocyst entrapment but also in hindered sporozoite mobility from oocysts according to scanning electron microscopy (SEM) analyses. Early parasite-induced bovine monocyte activation, accompanied by membrane protrusions toward C. parvum-oocysts/sporozoites, was unveiled using live cell 3D-holotomographic microscopy analysis. The administration of NF449, an inhibitor of the ATP purinergic receptor P2X1, to monocytes subjected to varying oxygen concentrations did not yield a noteworthy decrease in C. parvum-induced METosis. This suggests that the cell death process is not dependent on P2X1. Additionally, blockage of glycolysis in monocyte through 2-deoxy glucose (2-DG) inhibition reduced C. parvum-induced METosis but not significantly. According to monocyte energetic state measurements, C. parvum-exposed cells neither increased extracellular acidification rates (ECAR) nor oxygen consumption rates (OCR). Lactate monocarboxylate transporters (MCT) inhibitor (i.e., AR-C 141990) treatments significantly diminished C. parvum-mediated METs extrusion under physioxic (5% O₂) condition. Similarly, treatment with either DAPT or compound E, two selective Notch inhibitors, exhibited no significant suppressive effects on bovine MET production. Overall, for the first time, we demonstrate C. parvum-mediated METosis as P2X1-independent but as an MCT-dependent defense mechanism under intestinal physioxia (5% CO₂) conditions. METs findings suggest anti-cryptosporidial effects through parasite entrapment and inhibition of sporozoite excystation.

Interplay between Eimeria acervulina and Cryptosporidium parvum during In Vitro Infection of a Chicken Macrophage Cell Line (HD11)

BACKGROUND

Eimeria acervulina is a frequent intestinal pathogen of chickens, causing economic impact on the poultry industry. Cryptosporidium parvum is a neglected parasite in chickens. However, because of its zoonotic potential, poultry cryptosporidiosis may pose a risk to public health. Little is known about the parasite-host interactions during coinfection with both parasites. In this study, we investigated the possible interactions during in vitro coinfection of E. acervulina and C. parvum in a chicken macrophage cell line (HD11).

METHODS

HD11 cells were inoculated with E. acervulina and C. parvum sporozoites and incubated 2, 6, 12, 24, and 48 h post infection (hpi). Mono-infections for each parasite were also investigated. Real-time PCR was used to quantify parasite replication. Additionally, macrophage mRNA expression levels of IFN-γ, TNF-α, iNOS, and IL-10 were measured.

RESULTS

For both parasites, multiplication was, in most groups, lower in the coinfection group (COIG) compared with mono-infections. However, at 6 hpi, the number of C. parvum copies was higher in co-infections. Intracellular replication started to decrease from 12 hpi onward, and it was almost undetectable by 48 hpi in all groups. Infections resulted in low expression of all cytokines, except at 48 hpi.

CONCLUSIONS

Infection of avian macrophages with both E. acervulina and C. parvum seemed to hinder intracellular replication for both parasites in comparison to mono-infection. A clear reduction in intracellular parasites from 12 hpi onward details the important role potentially played by macrophages in host control of these parasites.

Cryptosporidium parvumcompetes with the intestinal epithelial cells for glucose and impairs systemic glucose supply in neonatal calves

Cryptosporidiosis is one of the main causes of diarrhea in children and young livestock. The interaction of the parasite with the intestinal host cells has not been characterized thoroughly yet but may be affected by the nutritional demand of the parasite. Hence, we aimed to investigate the impact of C. parvum infection on glucose metabolism in neonatal calves. Therefore, N = 5 neonatal calves were infected with C. parvum on the first day of life, whereas a control group was not (N = 5). The calves were monitored clinically for one week, and glucose absorption, turnover and oxidation were assessed using stable isotope labelled glucose. The transepithelial transport of glucose was measured using the Ussing chamber technique. Glucose transporters were quantified on gene and protein expression level using RT-qPCR and Western blot in the jejunum epithelium and brush border membrane preparations. Plasma glucose concentration and oral glucose absorption were decreased despite an increased electrogenic phlorizin sensitive transepithelial transport of glucose in infected calves. No difference in the gene or protein abundance of glucose transporters, but an enrichment of glucose transporter 2 in the brush border was observed in the infected calves. Furthermore, the mRNA for enzymes of the glycolysis pathway was increased indicating enhanced glucose oxidation in the infected gut. In summary, C. parvum infection modulates intestinal epithelial glucose absorption and metabolism. We assume that the metabolic competition of the parasite for glucose causes the host cells to upregulate their uptake mechanisms and metabolic machinery to compensate for the energy losses.

Velásquez Z, Borggrefe T, Gärtner U, Kamena F, Taubert A, Hermosilla C. ATP Purinergic Receptor P2X1-Dependent Suicidal NETosis Induced by Cryptosporidium parvum under Physioxia Conditions

Cryptosporidiosis is a zoonotic intestinal disease that affects humans, wildlife, and neonatal cattle, caused by Cryptosporidium parvum. Neutrophil extracellular traps (NETs), also known as suicidal NETosis, are a powerful and ancient innate effector mechanism by which polymorphonuclear neutrophils (PMN) battle parasitic organisms like protozoa and helminths. Here, C. parvum oocysts and live sporozoites were utilized to examine suicidal NETosis in exposed bovine PMN under both 5% O₂ (physiological conditions within small intestinal tract) and 21% O₂ (normal hyperoxic conditions in research facilities). Both sporozoites and oocysts induced suicidal NETosis in exposed PMN under physioxia (5% O₂) and hyperoxia (21% O₂). Besides, C. parvum-induced suicidal NETosis was affirmed by total break of PMN, co-localization of extracellular DNA decorated with pan-histones (H1A, H2A/H2B, H3, H4) and neutrophil elastase (NE) by means of confocal- and immunofluorescence microscopy investigations. C. parvum-triggered NETs entrapped sporozoites and impeded sporozoite egress from oocysts covered by released NETs, according to scanning electron microscopy (SEM) examination. Live cell 3D-holotomographic microscopy analysis visualized early parasite-induced PMN morphological changes, such as the formation of membrane protrusions towards C. parvum while undergoing NETosis. Significant reduction of C. parvum-induced suicidal NETosis was measured after PMN treatments with purinergic receptor P2X1 inhibitor NF449, under both oxygen circumstances, this receptor was found to play a critical role in the induction of NETs, indicating its importance. Similarly, inhibition of PMN glycolysis via 2-deoxy glucose treatments resulted in a reduction of C. parvum-triggered suicidal NETosis but not significantly. Extracellular acidification rates (ECAR) and oxygen consumption rates (OCR) were not increased in C. parvum-exposed cells, according to measurements of PMN energetic state. Treatments with inhibitors of plasma membrane monocarboxylate transporters (MCTs) of lactate failed to significantly reduce C. parvum-mediated NET extrusion. Concerning Notch signaling, no significant reduction was detected after PMN treatments with two specific Notch inhibitors, i.e., DAPT and compound E. Overall, we here describe for the first time the pivotal role of ATP purinergic receptor P2X1 in C. parvum-mediated suicidal NETosis under physioxia (5% O₂) and its anti-cryptosporidial properties.

Cryptosporidium parvum alters glucose transport mechanisms in infected enterocytes

The parasite Cryptosporidium parvum Tyzzer 1912 destroys parts of the intestinal brush border membrane which is important for the uptake of nutrients like glucose. In this study, glucose transport mechanisms of the host cells (IPEC-J2 cells) infected by C. parvum were investigated. The mRNA expression levels of glucose transporters (GLUT) 1 and 2 and Na⁺-coupled glucose transporter (SGLT) 1 were compared in infected and uninfected cells over an infection time of 24-96 h by RT-qPCR. Furthermore, the protein expression of SGLT 1 and GLUT 2 was quantified in western blot studies. While the protein expression of SGLT 1 was not altered in infected cells, mRNA expression of SGLT 1 and GLUT 1 was significantly increased 24 h p. i. and decreased 96 h p. i. The mRNA expression of GLUT 2 was significantly decreased 24 h, 72 h, and 96 h p. i. and also correlated significantly with the infection dose at 72 h p. i. In contrast to that, the protein expression of GLUT 2 was significantly increased 48 h p. i., associated with a significantly higher intracellular glucose level in infected cells compared with control cells at that time point of infection. This points to an adaptation of the host cells' glucose uptake taking place in the acute phase of the infection. A better understanding of these molecular mechanisms following a C. parvum infection may probably lead to an improvement of therapy strategies in the future.

Toxoplasma gondii Oocyst Infectivity Assessed Using a Sporocyst-Based Cell Culture Assay Combined with Quantitative PCR for Environmental Applications

Toxoplasma gondii is a ubiquitous foodborne protozoan that can infect humans at low dose and displays different prevalences among countries in the world. Ingestion of food or water contaminated with small amounts of T. gondii oocysts may result in human infection. However, there are no regulations for monitoring oocysts in food, mainly because of a lack of standardized methods to detect them. The objectives of this study were (i) to develop a reliable method, applicable in biomonitoring, for the rapid detection of infectious oocysts by cell culture of their sporocysts combined with quantitative PCR (sporocyst-CC-qPCR) and (ii) to adapt this method to blue and zebra mussels experimentally contaminated by oocysts with the objective to use these organisms as sentinels of aquatic environments. Combining mechanical treatment and bead beating leads to the release of 84% ± 14% of free sporocysts. The sporocyst-CC-qPCR detected fewer than ten infectious oocysts in water within 4 days (1 day of contact and 3 days of cell culture) compared to detection after 4 weeks by mouse bioassay. For both mussel matrices, oocysts were prepurified using a 30% Percoll gradient and treated with sodium hypochlorite before cell culture of their sporocysts. This assay was able to detect as few as ten infective oocysts. This sporocyst-based CC-qPCR appears to be a good alternative to mouse bioassay for monitoring infectious T. gondii oocysts directly in water and also using biological sentinel mussel species. This method offers a new perspective to assess the environmental risk for human health associated with this parasite.IMPORTANCE The ubiquitous protozoan Toxoplasma gondii is the subject of renewed interest due to the spread of oocysts in water and food causing endemic and epidemic outbreaks of toxoplasmosis in humans and animals worldwide. Displaying a sensitivity close to animal models, cell culture represents a real alternative to assess the infectivity of oocysts in water and in biological sentinel mussels. This method opens interesting perspectives for evaluating human exposure to infectious T. gondii oocysts in the environment, where oocyst amounts are considered to be very small.

Improvement of in vitro evaluation of chemical disinfectants for efficacy on Cryptosporidium parvum oocysts

Cryptosporidium parvum has been suggested as a suitable target for in vitro efficacy testing of disinfectants. To improve validity of a method based on exposure of HCT-8 monolayers to C. parvum oocysts we here critically evaluate and we propose certain procedural steps needed for the validation of disinfectants. Within a range of 0.02% to 0.4%, sodium taurocholate at 0.2% stimulated infection most efficiently while preserving host cell integrity. The course of invasion was monitored for periods of 30-240min post infection (p.i.). FACS analysis revealed that the proportion of sporozoites liberated from oocysts in the presence of 0.2% sodium taurocholate increased within 120min of incubation but remained constant thereafter. Maximum invasion of cells measured by qPCR was reached 180min p.i. and therefore set as invasion endpoint. As monolayers harvested 24h or 48h p.i. did not differ in the quantity of parasite hsp70 gene copies, DNA extraction can be performed as early as 24h p.i. Incubation of oocysts with 20% H₂O₂ for 2h resulted in inactivation of more than 99.5% both at room temperature and 10°C and appeared thus suitable as positive chemical treatment control. Four washing procedures considered to remove potentially toxic residual disinfectant from oocyst suspensions were tested. An application of a combination of DMSO (Dimethylsulfoxid), Tween20 and WSH (water of standardized hardness) appeared most efficient without deleterious effect of disinfectant residuals on the cell monolayer viability when oocysts accordingly washed were applied. In conclusion, for standardized in vitro evaluation of chemical disinfectants in C. parvum infected HTC-8 monolayers. (i) excystation medium should contain 0.2 % sodium taurocholate. (ii) excystation medium should be replaced by growth medium after 180 min. (iii) monolayers should be harvested 24 h p.i. for DNA preparation. (iv) ocysts exposed to 20 % H₂O₂ should be included as positive controls. (v) disinfected oocysts should be washed with DMSO/Tween20/WSH before they are transferred to monolayers.

Efficient reduction of pathogenic and spoilage microorganisms from apple cider by combining microfiltration with UV treatment

Thermal pasteurization can achieve the U. S. Food and Drug Administration-required 5-log reduction of pathogenic Escherichia coli O157:H7 and Cryptosporidium parvum in apple juice and cider, but it can also negatively affect the nutritional and organoleptic properties of the treated products. In addition, thermal pasteurization is only marginally effective against the acidophilic, thermophilic, and spore-forming bacteria Alicyclobacillus spp., which is known to cause off-flavors in juice products. In this study, the efficiency of a combined microfiltration (MF) and UV process as a nonthermal treatment for the reduction of pathogenic and nonpathogenic E. coli, C. parvum, and Alicyclobacillus acidoterrestris from apple cider was investigated. MF was used to physically remove suspended solids and microorganisms from apple cider, thus enhancing the effectiveness of UV and allowing a lower UV dose to be used. MF, with ceramic membranes (pore sizes, 0.8 and 1.4 μm), was performed at a temperature of 10 °C and a transmembrane pressure of 155 kPa. The subsequent UV treatment was conducted using at a low UV dose of 1.75 mJ/cm(2). The combined MF and UV achieved more than a 5-log reduction of E. coli, C. parvum, and A. acidoterrestris. MF with the 0.8-μm pore size performed better than the 1.4-μm pore size on removal of E. coli and A. acidoterrestris. The developed nonthermal hurdle treatment has the potential to significantly reduce pathogens, as well as spores, yeasts, molds, and protozoa in apple cider, and thus help juice processors improve the safety and quality of their products.

A new in vitro model using small intestinal epithelial cells to enhance infection of Cryptosporidium parvum

To better understand and study the infection of the protozoan parasite Cryptosporidium parvum, a more sensitive in vitro assay is required. In vivo, this parasite infects the epithelial cells of the microvilli layer in the small intestine. While cell infection models using colon, kidney, and stomach cells have been studied to understand the infectivity potential of the oocysts, an ideal in vitro model would be readily-available, human-derived, and originating from the small intestine. In this study, we developed a reproducible, quantitative infection model using a non-carcinoma, human small intestinal epithelial cell type, named FHs 74 Int. Our results show that FHs 74 Int cells are productively infected by viable oocysts, and exhibit higher levels of infection susceptibility compared to other cell types. Moreover, infection rate of the sporozoites on the monolayer was found to be comparable or better than other cell types. We furthermore demonstrate that infection can be improved by 65% when pre-treated oocysts are directly inoculated on cells, compared to inoculation of excysted sporozoites on cells. Identification of a better infection model, which captures the preferred site of infection in humans, will facilitate studies on the host pathogenesis mechanisms of this important parasitic human pathogen.

Integration of halofuginone lactate treatment and disinfection with p-chloro-m-cresol to control natural cryptosporidiosis in calves

Two field studies were accomplished on a dairy farm in Saxony to compare different strategies for the control of natural cryptosporidiosis in newborn calves. In the first study, 96 newborn calves were allocated to four different groups immediately after birth. Calves of group H and of group HN were treated orally with 120 μg/kg body weight (BW) of halofuginone lactate daily during the first seven days of life. Calves of group C and of group CN were treated with a same volume of tap water. As an additional measure, the pens of groups HN and CN were disinfected with 3% Neopredisan 135-1^®(p-chloro-m-cresol), the pens of groups C and H remained non-disinfected. Faeces were examined semi-quantitatively for oocyst excretion using carbolfuchsin-staining and the clinical course was recorded. While disinfection alone (group CN) had no effect on oocyst shedding and diarrhoea, treatment with halofuginone lactate (groups H and HN) reduced oocyst shedding and diarrhoea significantly. Combination of treatment and disinfection (group HN) controlled cryptosporidiosis completely during the first two weeks after birth. However, prevalence of diarrhoea and oocyst shedding was higher in the third week of life in group HN than in any of the other groups. This delayed occurrence of cryptosporidiosis was not seen in study 2 when all calves were similarly protected by treatment and specific disinfection. Oocyst shedding was not observed in peripartal cows either by carbolfuchsin staining, ELISA or PCR.

Inactivation of exogenous endoparasite stages by chemical disinfectants: current state and perspectives

Chemical disinfection is common practice and inevitable to achieve sufficient control over parasites particularly in intensive animal housing systems. To identify suitable chemicals, reliable data on antiparasitic efficacy of disinfectants are required. This review summarizes recently published experience with procedures applied to evaluate the viability of a variety of endoparasites following physical or chemical stress. It is concluded that laboratory models used to assess antiparasitic efficacy of e.g. commercial disinfectants should consider the most resistant stages of both helminths and protozoa, i.e. ascarid eggs and coccidia oocysts. To ensure reproducibility and transparency, standardized protocols are pivotal. Such protocols are established on a national level (e.g. DVG guidelines in Germany); however, internationally accepted certification procedures are currently lacking.

In vitro determination of anticryptosporidial activity of phytogenic extracts and compounds

Cryptosporidiosis caused by Cryptosporidium spp. is an important diarrhoeal disease observed in farm animals and humans, especially in young or immunocompromised individuals. A novel cell culture assay for testing extracts and pure compounds against Cryptosporidium parvum in 96-well microplate format was established and evaluated. It is based on previously described indirect fluorescent antibody techniques and was optimised for higher sample throughput. Rapid assessment of minimal inhibitory concentrations (MICs) was done by checking each well microscopically for the presence or absence of parasite stages. As a novelty, parasite development was quantified by enumeration of clusters of secondary infection (CSI), which typically appeared upon infection with a distinct parasite inoculum after a defined incubation time. Host cell (HCT-8) viability was measured by an integrated non-destructive water-soluble tetrazolium salt assay (WST-1), which facilitated discrimination of antiparasitic activity from possible cytotoxic effects of a test compound against the host cells. Host cell viability was regarded unimpaired when cultures had 75% or more viability when compared to control cultures without test substance. In this study, a maximum density of distinguishable CSI was obtained when cultures were infected with 2.5 × 10(3) oocysts and incubated for 48 h. The applicable inoculum has to be optimised for each batch of oocysts and before each experimental series. Parasite development was inhibited completely by monensin at 134 nM and silymarin at 50 mg/mL. These concentrations were non-toxic to the host cells and comparable to literature data. The percentages of parasite inhibition were determined for monensin and a 50% inhibitory concentration (IC(50)) of 36.6 nM (27.4-45.5) and a 90% inhibitory concentration of 65.9 nM (54.8-90.2) were calculated. The introduced assay is economic because relatively low parasite numbers may be used. If MICs are determined, evaluation is fast, as each well is viewed only briefly under the fluorescence microscope for presence or absence of CSI. Furthermore it is highly critical because only full parasite inhibition is assessed. Counting of CSI is more laborious and time-consuming, but it allows calculation of parasite inhibition rates and parameters like the half maximal inhibitory concentration (IC(50)). This assay shall be used to assess anticryptosporidial activities of various plant waste materials and by-products from the food and the pharmaceutical industries in the course of the EU project SAFEWASTES. Comparison with in vivo models should be performed to further corroborate the results. Automated evaluation by flow cytometry might facilitate higher sample throughput and reduce operator bias.

Evolution of Cryptosporidium in vitro culture

This overview discusses findings from culturing Cryptosporidium spp. in cell and axenic cultures as well as factors limiting the development of this parasite in cultivation systems during recent years. A systematic review is undertaken of findings regarding the life cycle of the parasite, taking into account physiological, biochemical and genetic aspects, in the hope that this attempt will facilitate future approaches to research and developments in the understanding of Cryptosporidium biology.

Efficacy of amine-based disinfectant KENO™COX on the infectivity of Cryptosporidium parvum oocysts

Cryptosporidium parvum is a zoonotic protozoan parasite that may cause severe neonatal diarrhoea or even mortality in newborn ruminants: its oocysts are extremely resistant to normal environmental conditions and to most common disinfectants. KENO™COX, a patent pending amine-based formula, was tested for its ability to inactivate C. parvum oocysts. The Daugschies assay (2002), a standardized assay for chemical disinfection initially described for Eimeria spp., was adapted for C. parvum oocysts. KENO™COX diluted in water at 2% and 3% concentration and incubated with oocyst suspensions for 2h, allowed a significant reduction in viability, lysing 89% and 91% of oocysts respectively. Infectivity of the remaining C. parvum oocysts was assessed by inoculation to C57 Bl/6 neonatal mice. Each mouse received 2.5 μl of a suspension initially containing 500,000 oocysts before contact with KENO™COX. Six days post inoculation, the intestinal parasite load was significantly reduced by 97.5% with KENO™COX 2% compared to that of the mice inoculated with untreated parasites. KENO™COX 3% completely eliminated infectivity of oocysts. The number of oocysts remaining infectious in the inoculum treated with KENO™COX 2% was calculated from an inoculated dose-response curve: it was estimated at about 48.6 oocysts among the 500,000 oocysts initially treated corresponding to 99.99% of inhibition. These results demonstrate the high efficacy of KENO™COX against C. parvum oocysts. Combined with an appropriate method of cleaning, the application of KENO™COX may be a useful tool to reduce cryptosporidial infectious load on farm level.