The above list of attributes relate to Cryptosporidium spp, a protozoan parasite that is known to cause disease in mammals, including humans. It is therefore surprising to learn that there is such a diverse range of regulatory control surrounding Cryptosporidium.

At one extreme, laboratory regulation and data that must be admissible as evidence in a court of law (DWI, UK), through enhanced surface water treatment regulations (EPA, USA) to little or no regulation (Republic of Ireland). All three of these jurisdictions have had recent outbreaks impacting not only human health but also tourism and commerce.

There are other protozoans that are also implicated in human disease, e.g. Giardia, Plasmodium and Toxoplasma. However it appears that Cryptosporidium is the ‘emerging’ protozoan pathogen that is receiving the most attention. Indeed, within the last five years it has been reported that the number of published research articles on the subject of Cryptosporidium was equivalent to that for Campylobacter, itself the biggest cause diarrhoeal disease in humans.

Aetiology and epidemiology
Of the known species of Cryptosporidium, it is the zoonotic C. parvum and anthroponotic C. hominis that are most often associated with cryptosporidiosis in humans. The life cycle of the organism is completed within the human gut and transmission of the disease occurs upon the excretion of stable oocysts, each containing four infectious sporozoites, from the host into the environment. Human disease consists of watery diarrhoea, abdominal pain, vomiting and consequent weight loss.

Most commonly associated with waterborne infections, Cryptosporidium is also implicated in foodborne outbreaks involving fresh produce and processed meats. The significance of Cryptosporidium as a risk factor within food production has seen the development of risk assessment models within HACCP frameworks in those sectors of the industry where heat processing is minimal. As chemical control is largely ineffective, environmental control employs physical techniques, e.g. heat, sedimentation, flocculation and filtration. It is reported that ozonation and UV treatments are also effective against Cryptosporidium oocysts.

It is now accepted that Cryptosporidium is ubiquitous in the environment and thus will find its way into the food chain from time-to-time. New molecular techniques are improving the understanding of the epidemiology of outbreaks and are also reporting in real-time. Analysis at the subgenotype level allows sources of infection to be tracked, pathogenicity to be compared and may lead to the development of novel therapeutics.