Which two protozoa are not affected by normal chlorination or UV radiation?

Giardia lamblia and Cryptosporidium protozoan cysts are known for their resistance to standard disinfection methods such as chlorination and UV radiation. This resistance is particularly significant for water treatment and public health because it means that these protozoa can persist in drinking water sources despite typical disinfection practices.

Cryptosporidium, for instance, has a hardy cyst form that can survive in harsh environmental conditions and is less effectively removed by chlorine compared to other pathogens. This makes outbreaks of cryptosporidiosis a significant concern, particularly in areas where water treatment processes rely heavily on chlorination.

Giardia lamblia similarly forms cysts that can withstand harsh treatment conditions, necessitating more advanced treatment methods like filtration or the use of alternative disinfectants such as ozone or higher levels of chlorine for effective inactivation.

Understanding the resilience of these protozoa highlights the importance of thorough water treatment processes and continuous monitoring of water quality to prevent waterborne diseases.