Cryptosporidium parvum in Food and Water

Introduction

Cryptosporidium parvum is a parasite which has already causes significant public health problems in the water industry and is now emerging as a potential food contaminant. This parasite can be present in the intestinal tract of animals including cattle and sheep and can be excreted in stable form as an oocyst from infected hosts. The oocyst can then contaminate the environment and enter the water and/or food chain. The clinical symptoms of C. parvum infection include acute watery diarrhoea with abdominal pain, accompanied by vomiting and weight loss. The disease is usually self-limiting with a duration of 2-3 weeks, although it can last up to 6 weeks. However in immuno-compromised people the illness can become chronic and persistent. There is no specific antibiotics or clinical treatment available for treatment of this infection. While predominantly considered a water borne contaminant, Cryptosporidium parvum has also been linked to a small number of food borne outbreaks involving raw goats milk, tripe, salad, raw milk, offal and sausage and apple cider. To date, the source of many C. parvum infections have never identified due to a lack of routine methods for the detection of this pathogen and there is sparse data available on the risk the parasite poses in foods.

Recognising the importance of this emerging organism and the need for more information on the risks that it poses, the EU in 2000 through the Fifth Framework Programme "Quality of Life and Management of Living Resources" funded a 3 year programme on the parasite to generate information which could be used to establish the risk posed by C. parvum in food and water "A risk assessment of Cryptosporidium parvum an emerging pathogen in the food and water chain in Europe" (QLK1 CT 1999 00775). A multidisciplinary team of scientists from 6 European countries conducted the programme. The main focus of the programme was to

• Develop routine procedures for the isolation and detection of C. parvum from different matrices (food, waste-water, slurries/faeces)
• Conduct studies to establish the prevalence of C. parvum in the food chain
• Conduct studies to establish the typical survival of C. parvum in the food chain
• Establish the effectiveness of current or novel control measures for C. parvum in food and water
• Develop quantitative risk assessment models for C. parvum in food and water using appropriate software.

The focus of this conference will be to present and review the results, which have been generated through this EU programme.

Papers included in this proceedings review novel detection and typing methods which have developed through the programme. These include papers by Clarke et al. who review the "The use of Commercial Products for the Detection of Cryptosporidium oocysts throughout the Food Chain" and papers by Lowery et al on "Improved detection and viability assessment of Cryptosporidium parvum using real-time NASBA and Light Cycler assay" and Cacciò on "Molecular identification of species/genotypes of Cryptosporidium in clinical and environmental samples".

The role of C. parvum as a potential food poisoning agent was a core issue addressed in the EU programme. Specific methods for the detection of C. parvum from beef and salad crops were developed and used in subsequent studies on the prevalence of the parasite in these matrices and on its potential to survive if present in these foods. The results generated are overviewed in papers by McEvoy et al on "The role of beef in the transmission of Cryptosporidium parvum" and Warnes and Keevil on "Survival of Cryptosporidium parvum in faecal waste and salad crops".Enemark et al review their studies on how environmental conditions affect the survival of C. parvum in their paper on "Effects of environmental conditions on Cryptosporidium oocyst viability".

The information generated throughout the project together with data from the literature was used in the development of preliminary risk assessment models. These models suggest in the main that the risk posed by C. parvum intreated potable water and in beef is minimal while a small risk may be posed by contaminated salad crops. The models for food are preliminary, being based principally on the limited amount of data generated through this current programme. They can hopefully be built upon in the future as more research is conducted on this topic and further surveillance data from across Europe is generated. These models are described by Hoornstra and Hartog in their paper "A quantitative risk assessment on Cryptosporidium in food and water"

The proceedings also include two invited contributions, which take a strategic view of the problems posed by C. parvum. Dr Rachel Chalmers, Cryptosporidium Reference Unit, PHL, Swansea, Wales reviews how improvements in molecular typing techniques can improve our understanding of how C. parvum is transmitted to humans in her paper entitled "Towards improved understanding of the molecular epidemiology and transmission of cryptosporidiosis: the development of a national collection of Cryptosporidium isolates". Dr Derval Igoe, The National Disease Surveillance Centre, Ireland overviews an Irish National Report which deliberated on and made recommendations on how Cryptosporidium should be monitored and regulated in potable and recreational water in Ireland. "Report from the Waterborne Cryptosporidiosis Subcommittee of the Scientific Advisory Committee of the Irish National Disease Surveillance Centre"

The final paper in the proceedings "Research & Cryptosporidium: future challenges" by Moore et al looks toward the future and speculates on how improvements in detection technologies in particular will improve our knowledge on emerging parasites such as C. parvum