Chlorination - an overview

21 Jul.,2022

Prevention The prevention of giardiasis requires proper handling and treatment of water used for com


Water Treatment Chemicals


The prevention of giardiasis requires proper handling and treatment of water used for communities and good personal hygiene. Although halogenation (e.g., chlorine and iodine) alone is sufficient to killG. lamblia cysts, important variables, such as water temperature, clarity, pH, and contact time, alter the efficacy of chlorine, and higher chlorine levels (4–6 mg/L) may be required.72,230 Thus, in addition to chlorination, public water supplies intended for drinking should also be subjected to coagulation-flocculation, sedimentation, and filtration.69

Travelers to low-income regions of the world or to wilderness areas should consider all water potentially contaminated because of the wide array of animal and human reservoirs of giardiasis. Bringing water to a boil is sufficient to kill all protozoal cysts; at high altitudes, boiling for a minute is reasonable. If boiling is impossible, halogenation is generally effective forGiardia, butCryptosporidium is resistant.72,230 There are many chlorine-based (e.g., chlorine bleach: 5% to 6%, 2 to 4 drops/L) or iodine-based (e.g., tincture of iodine: 2%, 5 drops/L) preparations in liquid or tablet form.230 Contact time should be increased for water that is cold, and the concentration of halogen should be increased for turbid water. Personal water filters with pores of an “absolute” micron size of 0.2 to 1.0 µm can be used.230 Filtered water should also be halogenated to kill enteric viruses if they are considered a risk. Uncooked foods that may have been washed or prepared in contaminated water should be avoided.

Giardiasis outbreaks in daycare centers can be difficult to resolve. Some recommend that only symptomatic children be treated; however, infected children transmitGiardia to parents and family members, with further potential spread to the community. Therefore, each situation requires an individual decision. If strict hand washing and treatment of symptomatic children fail to control an outbreak of diarrhea, consideration can be given to treating all infected children.231 Treatment-based strategies for transmission prevention in endemic settings, however, have not proven beneficial. Although metronidazole exposure within the previous 7 days decreased the likelihood ofGiardia detection60 in separate community-based studies of children in high-transmission endemic settings, community-based administration of metronidazole, albendazole, or nitazoxanide did not diminishGiardia prevalence.118,195,232

Human milk can be protective againstGiardia. Both human and animal breast milk can contain anti-Giardia antibodies; studies have demonstrated protection of breastfeeding infants from symptomatic infection.114,233,234