By Randall S. White and Peter M. Wallis, Hyperion Research Ltd., Medicine Hat
Giardia and Cryptosporidium are microscopic single-celled parasites capable of infecting humans and animals. They are commonly found in surface water sources that have been contaminated by human or animal sewage, and host infection may result from consumption of a small number of parasites.
Both giardiasis or 'Beaver Fever' (caused by Giardia), and cryptosporidiosis (caused by Cryptosporidium) can produce symptoms of diarrhoea, nausea, cramps, bloating, weight loss, and other gastrointestinal symptoms generally lasting 2-6 weeks. Symptoms may last longer and be more serious in children and adults with immune deficiencies.
The parasite enters the host in the form of microscopic cysts from which the parasites emerge when ingested. The parasites then begin to reproduce and attach to the wall of the host's intestine, ultimately producing the symptoms described above (within 6-16 days for Giardia and 2-25 days for Cryptosporidium). Mature parasites detach from the intestinal wall and form cysts which are passed in the faeces. About half of those infected with giardiasis have no symptoms and continue to pass cysts in their faeces but asymptomatic cryptosporidiosis is rare.
In cyst form, Giardia and Cryptosporidium are very resistant to chlorination and able to survive and remain infective for up to two months in cold water. Because faeces passed by infected hosts may contain large numbers of viable cysts, contamination of water sources with human sewage or animal waste causes a high potential risk of infection to humans consuming the contaminated water.
Drying is a good way to kill many pathogens on dishes, utensils and countertops.
Make sure that these items are completely dry before they are put away.
Other factors which may increase the risk of infection are wild animal access to water sources, and disruptions in normal treatment procedures due to either environmental factors such as flooding or ice breakup, or operation or equipment problems in the actual treatment process.
On the prairies, dugouts, rivers and streams are important sources of drinking water for both humans and animals, and households and small communities often have limited provision for water treatment. Limiting the introduction of faecal material to raw water sources by restricting human and animal access and eliminating possible sewage discharge is the first line of defence against Giardia and Cryptosporidium contamination of drinking water. This is particularly true where no water treatment takes place, or where chlorination is the sole method of treatment. In fact, when chlorine contact time is short, protection of the water source may be the best defence against waterborne giardiasis or cryptosporidiosis. If access to catchment areas can be controlled, contamination of surface waters can be reduced, thus reducing the risk of waterborne disease. A review of activities in catchment areas and testing of raw and treated drinking water are useful to ensure the safety of potable water and to test treatment effectiveness.