Any ideas on this will be appreciated Quantitative Microbial Risk Assessment (6

Question

Any ideas on this will be appreciated Quantitative Microbial Risk Assessment (6 pts) (Note please refer to slides on risk assessment for all abbreviations used to describe question below). A new city is being planned in rural Uganda that has a raw water source containing the following pathogens: Cryptosporidium parvum at a concentration of 1 oocyst per liter, E. coli 0157:H7 at a concentration of 10 cells per liter and rotavirus at 1 infectious unit per liter. Currently the city is proposing to use only free chlorine disinfection (PT = 0.999 for bacteria and viruses, PT = 0.9 for protozoan parasites) to treat its water. As an expert on drinking water and health, you are asked to do a risk assessment for cryptosporidiosis, E. coli and rotavirus diarrhea and to recommend any changes in the water supply that may be needed to reduce the infectious disease risks of these a. Knowing that the water contains 1 C parvum oocyst, 10 E. coli cells and 1 infectious rotavirus per liter and assuming people drink 2 liters of water per day, you calculated the daily and annual risks of cryptosporidium infection and illness, E. coli infection and illness and rotavirus infection and illness per person. Below are the results of your calculations. Review the calculations and discuss the results Which pathogen may cause the most severe outcomes? Are the annual infection risks greater than 1 in 10,000 10") per year for any of the pathogens? If yes, for which one and which pathogen poses the greatest risk of infection? Which pathogen may cause the most severe outcomes? (3 pts) C. parvum Risk Assessment Raw water quality = C,-1 oocysts/L Treatment Effect = PT = 0.9 Drinking water quality = CD = CR x ( 1-PT) = l oocysts/L x (1-09) 0.1 Exposure by drinking water = E = CD Volume water S/L x2L=0.2 Risk of Infection/Day-P(mL,-E x r = 0.2 oocysts x 4x10 3=8x10-4 Risk of Infection/Year-Ponty 1-(1-Rift d>) 365-1-( 1

Explanation / Answer

a.

E.coli may cause most server outcomes, because there is more number of pathogens per litre compared to the other infectious agents. Yes, the annual risk factor is greater than 1 in 10,000 for E.coli infection. The greatest risk of infection is possible with the rotavirus infection, but severe outcomes are possible with E.coli.

b.

Drinking purified water is the best way to reduce the risk factor in the given case.

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