1. Pathogens and drinking water
Professor Nick Gray
Centre for the Environment
Trinity College
University of Dublin
© Tigroney Press

2. Pathogens and drinking water
Learning objectives:
To know the main pathogen categories
To be aware the key pathogens in drinking water
Methods involved in monitoring of pathogens

3. Disease Classification
Pathogens and drinking water
Disease Classification
Water associated diseases are classified according to their mode of transmission and the form of infection as:
Waterborne diseases
Water-washed diseases
Water-based diseases
Water-related diseases
All drinking water disease in W. Europe currently classified as waterborne

4. Pathogens and drinking water
Waterborne diseases
Caused by contamination of water by faecal matter and urine
Infection by direct ingestion of water or indirectly by any ingestion of pathogens (e.g. food-Typhoid Mary)
Results in widespread outbreak of disease amongst those using the same source of water
Carriers may be symptomless
Example: Cholera, infectious hepatitis, paratyphoid, tularaemia, typhoid, amoebic dysentery, bacillary dysentery.
Weil’s diseases (leptospirosis) caused by skin contact with infected rat urine found in sewage, flood water and contaminated surface water.

5. Water-washed diseases
Pathogens and drinking water
Water-washed diseases
Caused by poor personal hygiene due to water shortages
Spread of infection reduced by supplying additional water. Microbial quality unimportant as used for cleaning/washing not ingestion
Diseases normally skin infections, mucous membranes and eyes. Non-faecal in origin (e.g. bacterial skin sepsis, scabies, cutaneous fungal infections).
Diseases also include those spread by fleas, ticks and lice (e.g. epidemic typhus, rickettsial typhus and louse-borne fever).
Some water borne diseases can be contracted due to poor personal hygiene (e.g. shigellosis)
Other examples: ascariasis, conjunctivitis, leprosy, skin sepsis

6. Pathogens and drinking water
Water-based diseases
Caused by pathogens that have complex life cycle requiring an aquatic intermediate host
Disease can not be contracted by ingestion or contact with pathogen as excreted by infected person
All caused by parasitic worms with severity of infection dependent on number of worms infecting host
Schistosomiasis caused by trematode Schistosoma spp. Aquatic snails intermediate host, cercarias penetrate skin of humans normally spread via irrigation schemes. Eggs leave humans via urine. >200 million people infected globally.
Other examples: Dracunculus medimensis - guineaworm (nematode) - Cyclops spp. intermediate host.

7. Water-related diseases
Pathogens and drinking water
Water-related diseases
Pathogens carried by insect vectors living near water
Diseases are all severe and difficult to control
Viral diseases
Yellow fever – mosquito Aedes spp.
Dengue – mosquito Aedes aegypti
Protozoan diseases
Gambian sleeping sickness (trypanosomiasis) – river tsetse fly Glossina spp.
Malaria – protozoan Plasmodium sp. Carried by mosquito Anopheles spp.

8. Controlling Pathogen transfer
Pathogens and drinking water
Controlling Pathogen transfer
Ideally drinking water should be free from all micro-organisms -unattainable goal in practice
Barrier approach:
(i) Wastewater treatment
(ii) Natural self purification
(iii) Water treatment
Point-of-use techniques
Monitoring
Barrier approach has been largely successful given huge reductions in outbreaks of primary pathogens.

9. Pathogens and drinking water

10. Monitoring Far too many pathogens to monitor them all
Pathogens and drinking water
Monitoring
Far too many pathogens to monitor them all
Use of indicator organisms to indicate contamination
Based on theory that there is a quantifiable relationship between indicator density and potential health risks

11. Pathogens and drinking water
All waterborne pathogens have certain traits that make them so successful:
An ability to be excreted in faeces in large numbers during illness
Failure of conventional sewage treatment to remove them
Survive as an environmentally robust form
Resilience to inactivation while in aquatic environment
Largely resistant to common disinfects used in water treatment
Only require small numbers to elicit infection in host consuming or exposed to water
These factors compounded by difficulty in detecting them in resources and effluents.

12. EU Drinking Water Directive specifies numerical standards for:
Pathogens and drinking water
EU Drinking Water Directive specifies numerical standards for:
Escherichia coli (0/100ml)
Enterococci (Faecal streptococci) (0/100ml)
Routine monitoring
Coliform bacteria (0/100ml)
Clostridium perfringens (0/100ml)
Bottled water
E.coli (0/250ml)
Enterococci (0/250ml)
Pseudomonas aeruginosa (0/250ml)
Heterotrophic bacteria 22oC (100/ml)
Heterotrophic bacteria 37oC (20/ml)
Membrane filtration on mEnterococcus agar – maroon colonies are enterococci

13. Main groups able to survive different periods:
Pathogens and drinking water
Main groups able to survive different periods:
Enterococci die quickly outside host indicates recent contamination
E.coli can survive for several weeks under ideal conditions – easily detected.
Sulphate reducing clostridia survive indefinitely in water – when above are absent indicates remote or intermittent contamination- useful in reservoirs.
Heterotrophic bacteria commonly found and reproduce in water- some now considered opportunistic pathogens- not direct indicator of faecal contamination- do indicate potential for pathogen survival and regrowth- EU DWD requires no significant increase above background levels in either tap or bottled water.

14. Enumeration techniques
Pathogens and drinking water
Enumeration techniques
Quantitative:
Membrane filtration used for all except Clostridium as requires anaerobic conditions (i.e. multiple tube method). Used in EU
Presence:absence:
Based on enzyme detection- Incubated 24h at 35oC- also quantitative as well as PA – used in US
Total coliforms presence of ß-galactosidaese activity (ONPG)
E. coli presence ß-glucuronidase activity (MUG)
Gene probe technology:
Allows single cells to be identified.

15. Pathogens and drinking water
Membrane filtration
Medium varies with many new ones on the market – specified methods linked to standards

16. Pathogens and drinking water

17. Main Irish/UK pathogens
Pathogens and drinking water
Main Irish/UK pathogens
Two protozoan diseases common
Giardia lamblia – giardiasis – backpacker’s disease
Crytosporidium parvum / hominis– cryptosporidiosis
Giardia
Lives in wide range of animals lives as trophozoite form (free-living) in intestines
Shed cysts: Oval 8-14 µm long 7-10 µm wide
One of the commonest causes of waterborne disease
US 71% raw 17% treated contain cysts
Scotland 48% raw and 23% treated
Symptoms explosive watery foul smelling diarrhoea, gas, nausea
Filter or boil 20 minutes

18. Pathogens and drinking water
Giardia: Top right: schematic of trophozite; Below right: trophozites X1000, Left: Life cycle

19. Pathogens and drinking water
Cryptosporidium
C. parvum can be differentiated into two distinct genotypes.
Genotype 1 or H (for human) exclusively human now named as C. hominis. Very aggressive and was the cause of the 1993 outbreak in Milawakee.
Genotype 2 or C (for calf) traditional C. parvum which has now been found in over 150 species including humans.
Both genotypes are commonly recorded in water supplies, but it is also readily spread from person to person as well as being auto-infective.
Oocysts ovoid 4-7 µm diameter; Infected animals and humans shed 1010 oocysts during course of infection; 1 cyst infects
UK 50% and in US 97% surface water affected
1989 Swindon/Oxford outbreak led to operational changes
Self limiting gastroenteritis, often fatal in immuno-suppressed
Spring/autumn peaks

20. Bacteria Primary: major diseases causing gastroenteritis
Pathogens and drinking water
Bacteria
Primary: major diseases causing gastroenteritis
Salmonella – typhoid, paratyphoid
Shigella – bacterial dysentery
Vibrio cholerae – cholera
Campylobacter – enteritis – dog and pets carry disease
Enteropathogenic E. coli- many strains- traveller’s tummy
e.g. Enterohaemorrhagic E.coli (0157.H7)- haemorragic colitis leading to kidney disease in children, also associated with food

21. Primary pathogen: Cholera (Vibrio cholerae)
Pathogens and drinking water
Primary pathogen: Cholera (Vibrio cholerae)
Increasingly common due to increased mobility and speed of travel
Healthy symptomless carriers 2-9% of population
Haemolyic strain 25% carrier
organisms needed to cause illness – not person to person
Primarily water transmitted or food handled by carrier.
Two serotypes 01 and 0139 responsible for epidemic cholera
0139 responsible for new world wide epidemic (8th pandemic)
Symptoms sudden diarrhoea with copious watery faeces, vomiting, suppression of urine, rapid dehydration, lowered temperature and blood pressure, collapse.
60% death rate – death a few hours on first showing symptoms
Rapid treatment death rate reduced to 1%

22. Pathogens and drinking water
Vibrio cholerae
2 um
_________________

23. Pathogens and drinking water
Factors involved in the spread of cholera is air transport, frequency of natural and man-made disasters exacerbated by climate change. Note: reporting has also improved

24. Opportunistic pathogens
Pathogens and drinking water
Opportunistic pathogens
Part of normal heterotrophic flora of aquatic systems
Not a threat to healthy people
At risk: newborn, elderly, immuno-compromised
List very long – most important: Mycobacteria spp, Legionella pneumopila and Aeromonads spp.
Readily multiply in distribution system and/or household plumbing.

25. Legionnaires’ Disease (Legionella pneumophila)
Pathogens and drinking water
Legionnaires’ Disease (Legionella pneumophila)
1976-American Legion annual conference in Philadelphia hotel
,000 cases in US 11,250 deaths
Bacteria survive and grow in phagocytic cells and multiply in the lungs causing bronchopnemonia and tissue damage
Very dangerous, high death and disability rates
Widespread in nature – readily colonizes supply pipes, resistant to disinfection
Domestic water supplies stored at 20-50oC plus key nutrients (e.g. Fe) and long retention time.
Mode of transmission as aerosols – showers humidifiers, air conditioning.
Problem in hospitals and hotels
Hyperchlorination, thermal eradication, UV sterilizers at point of use

26. Mycobacteria spp. Common in all natural waters
Pathogens and drinking water
Mycobacteria spp.
Common in all natural waters
Causes soft tissue damage-especially pulmonary disease and cervical lymphadenopathy
Disseniated mycobacterial disease third most common terminal infection of AIDS patients
Common in all waters, many pathogenic species, can get into system due to poor chlorination, able to colonize and grow in distribution systems (flats, offices, hospitals) due to slow moving water.

27. Viruses 120 distinct types of human pathogenic viruses
Pathogens and drinking water
Viruses
120 distinct types of human pathogenic viruses
In drinking water gastrointestinal illness caused by enteric viruses (e.g. enteroviruses, Rotaviruses, Astroviruses, Calciviruses, Hepatitis A, Norovirus and other small round viruses
Respiratory infections - Reovirus, Coxsackievirus, Echovirus,
Poliomyelitis – common in sewage due to live virus vaccination
Coxsachie B – associated with myalic encephalomyelitis (ME and cardiac disease
US - >20% all wells contaminated with viruses, common in surface water
Most warm blooded animals carry viruses pathogenic to man, especially dogs. Storm water major problem
Georgetown, Texas % of population contracted Hepatitis A after sewage was washed into groundwater supply by heavy rainfall.

28. Pathogens and drinking water
Conclusions
Pathogens are a continuous major risk to public health via drinking water
Barrier approach used to control pathogen transfer
Disinfection vital to prevent transfer
Detection difficult based on indicator organisms
Large volume of water need to be analysed for protozoa and viruses
Point of use systems best for opportunistic pathogens

29. References Pathogens and drinking water
Percival, S.L. et al. (2014) Microbiology of Waterborne Diseases: Microbiological Aspects and Risk (2nd Edition), Academic Press, London. Call No P42*1