2. The following table lists the etiologies of illness associated with drinking

Question

2. The following table lists the etiologies of illness associated with drinking and recreational waters in 1998. Which of the water samples would have shown a high coliform count? Which diseases could have been prevented by chlorinating the water? Briefly explain your answers. Agent Campylobacter jejuni Cryptosporidinam parvam E. coli 0157 H7 Giardia lamblia Naegleria fouleri Shigella sonne Number of Cases 100 1,432 164 83 3. Use the data shown below to explain how waterborne diseases can best be eliminated Filtration of trdrinking water 700 600 500 400 Chlorination drinking water 200 100 Year

Explanation / Answer

2. Answer:

Campylobacter jejuni: It is a gram negative, non motile rod shaped bacterium which causes Campylobacteriosis (type of gastroenteritis characterised by abdominal pain, diarrhea, fever and malaise). The source of infection is contaiminated water or food.

Cryptosporidium parvum: It is a coccidian protozoal parasite which causes Cryptosporidiosis characterised by acute, watery diarrhoea without blood. The source of infection is again contaminated food and water that contain oocysts (oocysts contain sporozoites of C. parvum that invade the host). It is more common in Immunocompromised individuals like HIV infected, malnourished etc

E.coli O157:H7: It is a serotype of E.coli which produces Shiga toxin and capable of producing Colonic escherichiosis. The source of infection is contaminated food, water and even raw milk that contains the pathogenic bacteria

Giardia lambia: It is a flagellated parasite which produces Giardiasis characterised by fatigue, nausea, diarrhea, greasy stools, anorexia, vomiting, bloating, abdominal cramps, weight loss. The source of infection is ingestion of contaminated water.

Naegleria fouleri: It is pathogenic amoeba that causes Naeglariasis (Primary amoebic meningoencephalitis). The source of infection is contaminated water through which the amoeba enters through nasal route upon inhalation. The amoeba is found in ponds, lakes, fresh warm waters, hot springs, river or minimally chlorinated swimming pools.

Shigella sonnei: It belongs to Enterobacteriaceae and a gram negative, rod shaped, non motile bacteria that causes Shigellosis. It is also spread by contaminated food or water.

From the above discussion all of the organisms can be spread through oro-fecal route (except Naegleria fouleri which spreads through nasal route) from water contamination. In the given table, The number of reported cases are high for C.parvum (1432), followed by E.coli 0157:H7 (164), C. parvum (100), S.sonnei (83), G. lambia (9), N. fouleri (4).

Chlorination of water causes disruption of the cell membrane of microorganisms causing cytolysis and cell death. Among the given microbes presented in the question, E.coli is the most susceptible microbe to chlorination However C.parvum, G.lamba are resistant to chlorination. The susceptibility and resistance to chlorination of given microbes are as follows:

C.parvum : Resistant to chlorination

E.coli 0157:H7: Highly susceptible

C. jejuni : Highly susceptible

S.sonnei: Susceptible than S. flexnari which also causes Shigellosis

G. lambia : Resistant to chlorination

N. fouleri : Highly susceptible

CONCLUSION:

So, Except C. parvum, G.lambia the other organisms can be destroyed by using Chlorination and the diseases associted can be prevented (Eschrichiosis, Gastroenteritis, Campylobacteriosis, Primary Amoebic Meningoencephalitis). As the cases reported are higher for E.coli, C.jejuni and Shigella when compared to others, their incidence could have been highly prevented when compared to other diseases of lesser incidence.

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Answer 3:

Introduction: Typhoid is caused by Salmonella typhi which is spread by contaminated water or food. Typhoid is characterised by Fever, abdominal pain, headache, rash.

From the chart given, it can be clearly understood that the incidence of water borne diseases are relatively less in the years of 1890-1895 which may be due to the less water pollution, less population, adequate water resources.

By the year 1900 where industrial revolution, surge in population led to the contamination of water bodies that led to rapid increase in Typhoid cases

Since typhoid is mainly spread by water contamination with S. typhi, Filteration can be effectively used to reduce the infection. Using filters with efficient pore size can filter the bacteria (whose size is 2-5 micrometers) and thus prevent the further spread of the disease.

This fact is evident from the graph shown, where, the number of cases have been decimated to very less numbers by the year 1910. But it should be remembered that filteration media used for filteration like cartridges, asbestos, membranes should be scrubbed and monitored to remove the entrapped bacteria which otherwise would lead to reinfection of the bacteria as bacteria are inoculated by the filteration media rather than being removed

Chlorination which forms Hypochlorous acid (HOCl), hypochlorite ions (OCl-) causes disruption of the cell membrane of microorganisms causing cytolysis and cell death. This is also a best method of prevention of water borne diseases, and in this case, it is the second best method which further reduced the cases in the years around 1915.

Public sanitation and awareness resulted in reduction of number of cases to a great extent by 1920, but emergence of resistance among S.typhi led to asymptomatic progression of the pathogen in the hosts. Carriers do not have the symptoms of disease but capable of transmitting the infection to the susceptible individuals.

Conclusion:

Filteration and Chlorination of drinking water can be used to reduce the spread of water borne diseases

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