waterborne pathogens: parasites
DESCRIPTION
Waterborne Pathogens: Parasites. February 23 rd -25 th , 2010. Parasitic pathogens in water. Enteric and non-enteric diseases Ingestion of contaminated water Contact with contaminated water Complicated life cycles taking place in water and the human body with intermediate hosts. - PowerPoint PPT PresentationTRANSCRIPT
Waterborne Pathogens: Parasites
February 23rd-25th, 2010
Parasitic pathogens in water
• Enteric and non-enteric diseases• Ingestion of contaminated water• Contact with contaminated water• Complicated life cycles taking place in water
and the human body with intermediate hosts
Categories of waterborne parasites
• Diseases contracted by ingestion of contaminated water
• Cryptosporidium• Entamoeba• Guinea worm disease
• Diseases contracted by contact with contaminated water
• Naegleria• Schistosomiasis
Cryptosporidiosis
• Cryptosporidium parvum• Protozoan parasite• Fecal-oral transmission• Humans and cattle are reservoirs• Contamination of water sources from cattle fields• Infectious stage is the extremely resistant
environmental stage (oocyst)• Resistant to chlorine disinfection• Diarrheal disease that can become chronic in
immunosuppressed people
Cryptosporidiosis
• Diagnosis through immunofluorescent staining and microscopy
Amoebiasis
• Entamoeba histolytica• Amoebic dysentery• Fecal-oral transmission• Infectious stage is the resistant environmental
stage (cyst)• Humans are reservoir• Disease is ubiquitous in areas of poor
sanitation
Amoebiasis
• Diagnosis via microscopy (fecal specimen)
Naegleria• Naegleria fowleri• Ubiquitous free-living amoeba• Reservoir: warm surface freshwaters• Primary amoebic meningoencephalitis• A common organism, but a rare disease• Infection by crawling up your nose into your
brain• Treatment with amphotericin B, but survival
rates are poor
Naegleria
• Diagnosis by microscopy of spinal fluid
Schistosomiasis
• Genus Schistosoma• Species mansoni, japonicum, and haematobiun• Blood flukes (parasitic worms)• Burden of disease is from chronic infection• Damage caused by eggs deposited in tissue
– Liver damage– Urinary tract damage
Schistosomiasis
• Humans are the main reservoir• Excrete eggs in feces• Important intermediate host: snails• Schistosomes live in the snail in freshwater• Infection from contact with water • Infectious stage is the cercariae• They leave the snail and penetrate skin • Migrate through the bloodstream to organs
Schistosomiasis
• Diagnosis by microscopy of eggs in stool or biopsy specimens
Schistosomiasis control
• Prevent contamination of water with adequate sanitation and disposal of feces
• Kill the cercariae by disinfection• Kill the intermediate host (molluscicides)• Drug treatment
– Praziquantel– Treatment of individuals who are infected– Mass drug treatment of communities as a
preventative measure
Guinea worm disease
• Dracunculus medinensis• Nematode (worm)• Humans are the reservoir• Intermediate host: small copepods that live
free in freshwater
Guinea Worm disease
• Worm larvae infect copepods• People ingest copepods, esp. when they drink
stagnant water• Larvae migrate from the stomach through the
body• Worms erupt though the skin• Putting affected areas of the body into water
releases the larvae to restart the cycle• Burden of disease from secondary bacterial
infections of skin lesions
Guinea Worm disease
• Diagnosis by microscopy of the larvae or seeing the worm crawl out of the skin
Guinea Worm control
• Target of a fairly successful eradication campaign
• Endemic only in Sudan, Ghana, Mali, Ethiopia• No effective drug treatment• Control by filtering water to remove the
copepods• Digging wells for safer water• Kill the copepods
Control of waterborne parasites
• Drinking water:• Prevention of water contamination
– ADEQUATE SANITATION• Barrier methods
– Treatment trains– Filtration– Most parasites are quite resistant to disinfection
Control of waterborne parasites
• Control of intermediate hosts (snails, copepods)
• Eliminating human infection to prevent further spread into the environment
• Preventing contact with high-risk sources