Inactivation of Cryptosporidium parvum oocysts and faecal indicator bacteria in cattle slurry by addition of ammonia

Application of hydraulic modelling and quantitative microbial risk assessment (QMRA) for cloudburst management in cities with combined sewer systems

Urban cloudburst management may include the intentional temporary storage of flood water in green recreational areas. In cities with combined sewers, this will expose the population visiting the area to sewage and increase the risk of diarrhoeal disease. We present a unique approach to estimate the risk of diarrhoeal disease after urban flooding. The exposure scenario was: rainwater mixed with sewage flows into a park; sewage with pathogens deposit on the grass; after discharge, a baby plays on the grass and is exposed to the pathogens in the deposited sewage by hand-to-mouth transfer. The work included modelling the transport of sewage into four parks intended to be flooded during future cloudbursts. A flood simulation experiment was conducted to estimate the deposition of pathogens from sewage to grass and transfer from grass to hand. Hand-to-mouth transfer, based on literature values, was used to estimate the ingested dose of pathogens. The probability of illness was estimated by QMRA. The estimated average probability of illness varied between 0.03 and 17%. If the probability of illness is considered unacceptable, the cloudburst plans should be changed, or interventions, e.g. informing the public about the risk or restricting access to the flooded area, should be implemented.

A Simple Alcohol-based Method of Oocyst Inactivation for Use in the Development of Detection Assays for Cryptosporidium

Cryptosporidium spp. are obligate, intracellular parasites that cause life-threatening diarrhea among children and immunocompromised adults. Transmission occurs by the fecal-oral route following ingestion of thick-walled oocysts that can contaminate, persist, and resist disinfection in water and food. Sodium hypochlorite, peroxides, ozone, formaldehyde, and ammonia are suitable disinfectants against Cryptosporidium oocysts. Effective concentrations of these chemicals can be toxic and not practical for downstream research use of non-viable oocysts. Oocyst inactivation approaches such as UV light, heat, and treatments with ethanol or methanol are generally more accessible for routine lab use, yet their applicability in Cryptosporidium assay development is limited. The aims of this study were to evaluate methods of inactivation of Cryptosporidium oocysts that can be readily applied in the laboratory and test the utility of whole inactive oocysts in quantitative PCR (qPCR). Experiments were performed on C. parvum oocysts subjected to heat (75 °C/10 min) or treated with increasing concentrations of ethanol and methanol over time. Viability assays based on propidium iodide (PI) staining, in vitro excystation, and infection of the Hct-8 cell line were used to evaluate the efficacies of the treatments. Excystation of sporozoites was not impaired with 24 h exposures of oocysts to 50% ethanol or methanol, even though significant PI incorporation was observed. Concentrations of ≥70% of these chemicals were required to completely inhibit excystation and infection of Hct-8 cells in vitro. Inactivated oocysts stored for up to 30 days at 4 °C retained cyst wall integrity and antigenicity as observed by light microscopy and immunofluorescence. Moreover, non-viable oocysts applied directly in qPCR assays of the COWP gene were useful reference reagents for the identification and quantification of Cryptosporidium in spiked water samples. In summary, we have established a practical approach to inactivate C. parvum oocysts in the laboratory that is suitable for the development of detection or diagnostic assays targeting the parasite.

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Disinfectant-based inactivation of oocysts is not feasible for assay development.

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Inactivation methods that retain antigen and nucleic acid integrity are limited.

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Alcohol-inactivated oocysts are suitable as reference reagents in qPCR.

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We present a method to effectively inactivate oocysts and retain assayable properties.

Cryptosporidium and cryptosporidiosis in wild birds: A One Health perspective

Cryptosporidium is one of the most important parasitic protozoa that can be transmitted through food and water contamination. With the increasing report of Cryptosporidium infections in wild birds, especially in herbivorous waterfowl, concerns have been raised for oocyst contamination of water and food supplies, which in turn can cause human and domestic animal infections in areas neighboring wild birds' habitats. This review discusses the epidemiology, species, and genotypes distribution of Cryptosporidium in wild birds around the world. The overall prevalence of Cryptosporidium in wild birds was calculated as 3.96% (1945/49129), with 6 Cryptosporidium species (C. andersoni, C. parvum, C. meleagridis, C. avium, C. baileyi, and C. galli) and 5 genotypes (Goose genotype I, Goose genotype II, Avian genotype I, Avian genotype III, and Avian genotype VI) reported. As wild birds mainly live in the wild, control method for the Cryptosporidium infection in wild birds is still lacking, which increases the probability of disease transmission from wild birds to humans. The main purpose of this review is to highlight the Cryptosporidium infection in wild birds and its transmission, associated risk factors, and their prevention, illustrating the necessity of multidisciplinary approaches toward screening and control of Cryptosporidium infections.