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  • Final Activity Report Summary - CRYPTONET.IE (Cryptosporidiosis Network Ireland: Development of Skills and Knowledge to Predict Cryptosporidiosis Risk in Catchment Waters)

Final Activity Report Summary - CRYPTONET.IE (Cryptosporidiosis Network Ireland: Development of Skills and Knowledge to Predict Cryptosporidiosis Risk in Catchment Waters)

The project encompassed three major activities: (1) spatial data analysis of small agricultural catchments; (2) characterisation of Cryptosporidium spp. in livestock in three sample catchments representative of agricultural catchments in Ireland and (3) understanding of the transport vector processes in the wider environment. Three agricultural catchments were surveyed during the project, one which was "clean" in which no clinical cases of cryptosporidiosis were seen in the animal population and two "infected" where clinical cases of neonatal cryptosporidiosis had been diagnosed.

Faecal samples were randomly taken from a representative number of 1 - 8 week old calves and adult bovines on farms in each catchment. Additional samples were taken from slurry storage tanks, field dung heaps, soils and surface waters. A number of modifications to the routine internationally accepted laboratory procedures were developed to ensure maximum analytical efficiency and in particular an efficient isolation of Cryptosporidium DNA from environmental samples, especially slurry and soil. A description of these aspects of the study is being prepared for publication. A paper describing an assessment, using Bayesian statistics, of the routine diagnostic tests for cryptosporidiosis including the recently developed real time PCR has been accepted for publication.

Spatial analysis of the infected catchments was performed in ArcGIS and a simple risk potential index has been developed and published. This considered land use, rainfall, soil type, slope, soil moisture deficit and distance from a watercourse as major risk factors. The index has the potential to be used to develop catchment management strategies to reduce risk of infection. It introduced the concept of temporal analysis as part of the risk assessment. The concept of a risk calendar was thus developed which linked risk of surface water contamination at a given time of year to the current agricultural and land use activity. This will be published soon.

Studies on the transport of oocysts were conducted at two scales: laboratory studies using soil columns and catchment modelling. These focused on three main aspects: the die-off rate of oocysts (critical to risk assessment), the binding of oocysts to soil particles and the transport and filtering of oocysts in soils. The publication of die-off rates in water, soil and faeces will improve future risk assessments. It was found that using constant pressure, rather than constant flux for soil column experiments better reflected the transport of oocyst that would occur in the soil environment and thus would provide better data for risk assessment. In addition a new technique for quantifying the binding of oocysts to soil particles was developed and will be published soon. This will allow development of catchment specific soil risk factors for future modelling work. Of the three catchments studied, only one was fully gauged (the clean catchment). For this reason a study was undertaken using SWAT 2005 to evaluate whether neighbouring gauged catchments could be used to parameterise the model, and whether the bacterial transport model could adequately capture the transport of protozoan oocysts.

It was found that SWAT 2005 could be made to perform reasonably well and slurry management (i.e. spreading on pasture) was identified as the key factor in oocyst contamination of surface waters. This has significant implications for public health monitoring because it means that the model can be used to identify high risk agricultural catchments with sparse hydrological data sets. The work will be published soon. Both qualitative and quantitative risk assessment methods were used with the data collected. A rigorous assessment of qualitative risk assessment was published that indicated more weight should be placed on the known incidence of infection and clinical symptoms in animals in a catchment and the timing of management events. A quantitative risk assessment procedure was assessed and confirmed. The results of this study will be published soon.

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