Pathogens in Water

1. Pathogens in Water October 16 2006

2. Water Pathogens in History 1854: Cholera outbreak in London, England Linked to a water pump from a polluted region of the Thames People served by pumps upstream showed low incidence of cholera

3. Water Pathogens in History 1855-1856: Typhoid fever in a street in Bristol, England associated with a single water pump People served by alternate pump unaffected Note: 30 years prior to identification of the causative agent for typhoid fever

4. Water Pathogens in History 1860’s: Pasteur demonstrated that fermentation is caused by microorganisms, and that those microorganisms do not occur by spontaneous generation

5. Water Pathogens in History 1880’s: Pasteur’s findings led to eventual acceptance of the germ theory of disease, and appreciation of water as a carrier of disease-causing organisms

6. Water Pathogens in History Early 1900’s: Death rates due to typhoid fever in cities on the Ohio river dropped from 75 deaths to 15 per 100 000 people Due to installation of drinking water treatment plants

7. Water Pathogens in History 1920-1960: Water-borne disease outbreaks in the US decreased steadily in direct relation to increase in chlorination systems 1960-present: Outbreaks have increased. Due to an actual trend, or due to increased identification of disease sources? Pathogens in drinking water remains a serious problem in developing countries

8. Contamination of Water Supplies 10%: chemical contamination 40%: microorganism contamination 50%: unidentified contamination based on surveys 1971-1978 Water supplies are used by populations Transmission of water-borne pathogens may be expressed as epidemic or endemic

9. Time Course of an Epidemic

10. Water-Borne Epidemics Propagation via domestic effluent and re-introduction through infected waste Examination of microorganisms in domestic waste can indicate degree and variety of infection in the population Identification of drinking water infections can be difficult due to long incubation times

11. Controlling Epidemics Control the source (sewage effluent) Control the vector (water supply) Immunize the population Relatively pathogen-free water supply in developed countries Success breeds complacency: lowered rate of immunization, renewed incidence

12. Water-Borne Epidemics Generally viruses, bacteria or protozoa Typically cause intestinal disease, contaminating water supply in fecal material and re-infecting by ingestion Survival periods in water vary: Cellular viruses < bacteria < protozoa Survival varies with salinity, temp, etc.

14. Viruses 100+ known water-borne enteric viruses Infectious hepatitis, poliovirus and viral gastroenteritis are of practical concern Found in sewage and polluted rivers Tests for presence of viral particles in water supplies are difficult and unreliable

15. Viruses Little known about survival, concentration distribution of viruses in water Generally survive < 3 months in water Can survive up to 5 months in sewage Tend to be adsorbed onto surfaces Minimum infectious dose may be a single viral particle

16. Bacteria Largest group of water-borne pathogens Minimum infectious dose of 103-105 cells Usually poor competitors at low substrate levels in natural waters Eliminated by competition and predation Survival may be prolonged by low T, sediment adsorption, anoxic conditions

17. Common Bacterial Pathogens Shigella sp.: cause of dysentery almost strictly human affliction shigellosis and salmonellosis epidemics in developed countries tend to be food-borne transmission by drinking water major route in undeveloped countries rapid die-off in sewage 25 d @ 13oC, 4 d @ 37oC

18. Common Bacterial Pathogens Salmonella spp.: causes of salmonellosis Food poisoning Low incidence, peaks in mid-late summer Carried by 1-4% of the population, plus farm animals (13-17%) and wild animals Generally cause gastrointestinal diseases; Salmonella typhi causes Typhoid fever

19. Common Bacterial Pathogens Enteropathogenic E. coli: gastroenteritis and urinary tract infections (UTI) Carrier rates vary: 16% in mothers of newborns, 7% in food handlers, 3% in children Carried by farm animals E. coli in effluents to natural waters reduce to 5% within 5 days

20. Common Bacterial Pathogens Francisella tularensis: tularemia (rabbit fever; flu-like symptoms) Vectors are ticks, rodents, direct contact with sewage, water contaminated by rodents Disease spreads via lymphatic system and bloodstream (primarily macrophages) Grows intracellularly, causes lesions in skin, lungs, liver, spleen and brain

21. Common Bacterial Pathogens Leptospira sp.: Leptospirosis Begins as a wound infection Occupational disease among workers in contact with polluted water Carried by pigs, dogs, rodnts and humans Excreted in urine of infected animals

22. Common Bacterial Pathogens Vibrio cholerae: Cholera Highly contagious V. cholerae infect small intestine Healthy carriers make up from 1-9% to 25% of population Causes water loss; treat with aggressive rehydration and electrolyte replacement

23. Cholera Toxin Induces the cycstic fibrosis transmembrane conductance regulator (CFTR) protein to produce watery diarrhea, leading to water and electrolyte loss

24. Protozoa Enter host body through ingestion Generally in cyst form (encapsulated in carbohydrate shell) Major water-borne pathogenic protozoa are Giardia intestinalis and Entamoeba histolytica

25. Giardia intestinalis Flagellated cyst 1-10 cysts required for infection Causes serious diarrhea Sources: Humans; beavers often implicated

26. Entamoeaba histolytica Causes amoebic dysentery: “Montezuma’s Revenge” - bloody diarrhea Survives for long periods at low temperatures and damp conditions in clean water Survives only a few days in fecal material

27. Recent Protozoan Outbreaks Cryptospiridium: gastrointestinal disease outbreaks in North American cities (including K-W) Cyclospora cayetanensis: associated with imported fruit that has been in contact with feces