Persistence and survival of Cryptosporidium parvum oocysts on lamb's lettuce leaves during plant growth and in washing conditions of minimally-processed salads

Novel strategy to quantify the viability of oocysts of Cryptosporidium parvum and C. hominis, a risk factor of the waterborne protozoan pathogens of public health concern

While waters might be contaminated by oocysts from >40 Cryptosporidium species, only viable oocysts of C. parvum and C. hominis truly pose the main health risk to the immunocompetent population. Oocyst viability is also an important but often neglected risk factor in monitoring waterborne parasites. However, commonly used methods in water monitoring and surveys cannot distinguish species (microscopic observation) or oocyst viability (PCR), as dead oocysts in water could retain gross structure and DNA content for weeks to months. Here, we report new TaqMan qRT-PCR/qPCR assays for quantitative detection of viable C. parvum and C. hominis oocysts. By targeting a hypothetical protein-encoding gene cgd6_3920 that is highly expressed in oocysts and variable between species, the qRT-PCR/qPCR assays achieve excellent analytical specificity and sensitivity (limit of quantification [LOQ] = 0.25 and 1.0 oocyst/reaction). Using calibration curves, the number and ratio of viable oocysts in specimens could be calculated. Additionally, we also establish a TaqMan-18S qPCR for cost-effective screening of pan-Cryptosporidium-positive specimens (LOQ = 0.1 oocyst/reaction). The assay feasibility is validated using field water (N = 43) and soil (79) specimens from 17 locations in Changchun, China, which detects four Cryptosporidium species from seven locations, including three gp60-subtypes (i.e., IIdA19G1, IIdA17G1 and IIdA24G2) of C. parvum oocysts showing varied viability ratios. These new TaqMan q(RT)-PCR assays supplement current methods in the survey of waters and other samples (e.g., surfaces, foods and beverages), and are applicable to assessing the efficiency of oocyst deactivation protocols.

Human dendritic cell interactions with the zoonotic parasite Cryptosporidium parvum result in activation and maturation

Cryptosporidiosis in humans is caused by infection of the zoonotic apicomplexan parasite Cryptosporidium parvum. In 2006, it was included by the World Health Organization (WHO) in the group of the most neglected poverty-related diseases. It is characterized by enteritis accompanied by profuse catarrhalic diarrhea with high morbidity and mortality, especially in children of developing countries under the age of 5 years and in HIV patients. The vulnerability of HIV patients indicates that a robust adaptive immune response is required to successfully fight this parasite. Little is known, however, about the adaptive immune response against C. parvum. To have an insight into the early events of the adaptive immune response, we generated primary human dendritic cells (DCs) from monocytes of healthy blood donors and exposed them to C. parvum oocysts and sporozoites in vitro. DCs are equipped with numerous receptors that detect microbial molecules and alarm signals. If stimulation is strong enough, an essential maturation process turns DCs into unique activators of naïve T cells, a prerequisite of any adaptive immune response. Parasite exposure highly induced the production of the pro-inflammatory cytokines/chemokines interleukin (IL)-6 and IL-8 in DCs. Moreover, antigen-presenting molecules (HLA-DR and CD1a), maturation markers, and costimulatory molecules required for T-cell stimulation (CD83, CD40, and CD86) and adhesion molecules (CD11b and CD58) were all upregulated. In addition, parasite-exposed human DCs showed enhanced cell adherence, increased mobility, and a boosted but time-limited phagocytosis of C. parvum oocysts and sporozoites, representing other prerequisites for antigen presentation. Unlike several other microbial stimuli, C. parvum exposure rather led to increased oxidative consumption rates (OCRs) than extracellular acidification rates (ECARs) in DCs, indicating that different metabolic pathways were used to provide energy for DC activation. Taken together, C. parvum-exposed human DCs showed all hallmarks of successful maturation, enabling them to mount an effective adaptive immune response.

Cryptosporidium and agriculture: A review

Cryptosporidiosis is a significant contributor to global foodborne and waterborne disease burden. It is a widespread cause of diarrheal diseases that affect humans and animals worldwide. Agricultural environments can become a source of contamination with Cryptosporidium species through faecal material derived from humans and animals. This review aims to report the main findings of scientific research on Cryptosporidium species related to various agricultural sectors, and highlights the risks of cryptosporidiosis in agricultural production, the contamination sources, the importance of animal production in transmission, and the role of farmed animals as hosts of the parasites. Agricultural contamination sources can cause water pollution in groundwater and different surface waters used for drinking, recreational purposes, and irrigation. The application of contaminated manure, faecal sludge management, and irrigation with inadequately treated water are the main concerns associated with foodborne and waterborne cryptosporidiosis related to agricultural activities. The review emphasizes the public health implications of agriculture concerning the transmission risk of Cryptosporidium parasites and the urgent need for a new concept in the agriculture sector. Furthermore, the findings of this review provide valuable information for developing appropriate measures and monitoring strategies to minimize the risk of infection.