Day 11: Giardia

Giardia is a protozoan parasite that can cause severe gastrointestinal problems when consumed in drinking water – it is commonly associated with “travelers diarrhea.”  A typical infection can result in sever cramping, diarrhea, nausea, dehydration and nutritional loss for 2-4 days.  This is often followed by 4-7 days of constipation.  There is no acceptable level of giardia in drinking water, as it is highly infectious, however because it requires more aggressive disinfection and filtration methods than typical microbiological contaminants, any weakly enforced treatment protocols can leave a water supply highly susceptible to an outbreak.

Giardia was discovered in 1681, by Antoine van Leeuwenhoek, who invented the first microscope.  By 1859 it was recognized as a parasite, however it was not until 1915, that it was widely recognized as a pathogen that could be passed via fecal contamination.  In 1954 it was observed that giardia cysts could survive in water, in the 1970’s it became associated with diseases contracted by international travelers.  Because giardia has proven more resilient to chlorine disinfection, it has been observed that UV disinfection as a superior method for preventing human consumption of giardia cysts in water.

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