What types of protozoa are known to infect water supplies?

Giardia lamblia and Cryptosporidium parvum are both well-documented protozoan parasites that can contaminate water supplies and lead to outbreaks of gastrointestinal disease in humans.

Giardia lamblia, commonly referred to simply as Giardia, is a flagellated protozoan that causes giardiasis, which can result in symptoms such as diarrhea, cramps, and nausea. It is often found in contaminated water sources, particularly in areas with poor sanitation or after heavy rainfall, which can lead to runoff.

Cryptosporidium parvum is another significant waterborne protozoan parasite. It causes cryptosporidiosis, which can also manifest as severe diarrhea and other gastrointestinal symptoms. It is resistant to many common disinfectants, making it a particularly troublesome contaminant in water supplies.

Collectively, these protozoa highlight the importance of ensuring clean water and the need for effective water treatment methods to prevent contamination. The other options mentioned include bacteria and viruses that, while they can also affect water safety, do not fit the category of protozoa. This specificity is crucial when discussing types of pathogens that can contaminate water.