Waterborne Pathogens: Parasites

1. Waterborne Pathogens: Parasites February 23rd-25th, 2010

2. 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

3. 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

4. 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

5. Cryptosporidiosis • Diagnosis through immunofluorescent staining and microscopy

7. 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

8. Amoebiasis • Diagnosis via microscopy (fecal specimen)

10. 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

11. Naegleria • Diagnosis by microscopy of spinal fluid

13. 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

14. 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

15. Schistosomiasis • Diagnosis by microscopy of eggs in stool or biopsy specimens

17. 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

18. Guinea worm disease • Dracunculus medinensis • Nematode (worm) • Humans are the reservoir • Intermediate host: small copepods that live free in freshwater

19. 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

20. Guinea Worm disease • Diagnosis by microscopy of the larvae or seeing the worm crawl out of the skin

22. 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

23. Control of waterborne parasites • Drinking water: • Prevention of water contamination • ADEQUATE SANITATION • Barrier methods • Treatment trains • Filtration • Most parasites are quite resistant to disinfection

24. 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