The agent is a protozoon; Cryptosporidium parvum
The organism has a complex life cycle that can take in a single animal host. It produces oocysts (diameter 4-6 micrometres) which are very resistant to chlorination but killed by conventional cooking procedures.
Symptoms
The incubation period is 2-4 days.
Persistent diarrhoea, nausea, vomiting and abdominal pain, sometimes accompanied by an influenza-like illness with fever.
The reservoir or source is humans, wild and domestic animals e.g. cattle. Children under the age 5 years are at a higher risk of infection. Immuno-compromised individuals may suffer from longer and more severe infection; may be fatal in AIDS patients.
The mode of transmission
It is spread through the faecal-oral route, person-to-person contact or consumption of faecal contaminated food and water, bathing in contaminated pools. Foods involved include raw milk, drinking-water and apple cider.
Control and Prevention
Pasteurization/sterilization of milk; filtration and disinfection of water; sanitary disposal of excreta, sewage and wastewater; thermal processing; good hygiene practices during production and processing.
In food service establishment boiling of water when safe water is not available; boiling of milk; thorough cooking of food; thorough handwashing.
Occurrence is worldwide.
