• In the U.S. the number of disease outbreaks due to drinking or recreational water contamination is relatively low • Worldwide, lack of adequate water treatment facilities and access to clean water contribute significantly to the spread of infectious diseases Waterborne infection
Waterborne infection. In the U.S. the number of disease outbreaks due to drinking or recreational water contamination is relatively low Worldwide, lack of adequate water treatment facilities and access to clean water contribute significantly to the spread of infectious diseases. - PowerPoint PPT Presentation
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• In the U.S. the number of disease outbreaks due to drinking or recreational water contamination is relatively low
• Worldwide, lack of adequate water treatment fa-cilities and access to clean water contribute sig-nificantly to the spread of infectious diseases
Waterborne infection
• Cholera– Severe diarrheal disease– Caused by Vibrio cholerae– Typically transmitted through ingestion of contaminated
water – Largely restricted to developing countries
• Endemic in Africa, Southeast Asia, the Indian subconti-nent, and Central and South America
– Can be controlled by application of water treatment
Waterborne infection: Cholera
• Pathogenesis– V. cholerae attaches to epithelial cells in the small in-
testine where it grows and releases enterotoxin
– This enterotoxin causes severe diarrhea • Can result in dehydration and death unless treated
• Diagnosis– Presence of V. cholerae bacilli in the “rice water” stools of patients
Waterborne infection: Cholera
• Prevention– Immunization not recommended– Public health measures are very important
• Treatment– Treated with oral rehydration and electrolyte replace-
• These organisms are found in nearly all surface waters and are highly resistant to chlorine due to cyst formation
Waterborne infection: Giardiasis and cryptosporidiosis
• Giardiasis– An acute gastroenteritis– Caused by a flagellated protist (Giardia intestinalis) that
is usually transmitted to humans in fecally contaminated water
– The protist cells produce a resting stage (cyst) that is re-sistant to desiccation and chemical disinfection
– Following ingestion, cysts germinate and attach to the in-testinal wall causing symptoms of infection
– Many individuals exhibit no symptoms and can act as carriers
Waterborne infection: Giardiasis
Cyst
• Cryptosporidiosis– An acute gastroenteritis– Caused by a protist (Cryptosporidium parvum) that
lives as a parasite in warm-blooded animals– Produces thick-walled, infective cells (oocysts) that
are shed in high numbers in the feces of infected ani-mals
– The oocysts are transmitted in fecally contaminated water
– Oocysts are highly resistant to chlorine and UV radia-tion
Waterborne infection: Cryptosporidiosis
• Legionellosis– Caused by Legionella pneumophilia– Normally transmitted in aerosols– Common in terrestrial and aquatic habitats– Relatively resistant to heating and chlorination– Common in cooling towers and evaporative condensers of
large air conditioning systems• The pathogen grows in the water and is disseminated in
humidified aerosols– Infection is not spread from person to person