Presentation at 3rd GRF One Health Summit 2015 Session OH Approaches For Sustainable Development

1. One Health perspective and assessment of Giardia &
Cryptosporidium infections related to wastewater &
excreta use in agriculture in Vietnam
Dr. Phuc Pham-Duc
Center for Public Health and Ecosystem Research (CENPHER) – HSPH
Vietnam One Health University Network (VOHUN)
Email: pdp@vohun.org
3rd
GRF ONE HEALTH SUMMIT 2015
Fostering interdisciplinary collaboration for global public and animal health
Davos, 4-6 October 2015

2. Contents
• Introduction
• Study aim
• Study sites
• Methods
• Results
• Conclusions
• Acknowledgement

3. Introduction
Wastewater and excreta use in agriculture
• Using wastewater to grow food reduces the use of
others surface & ground water.
• In Vietnam, the use of wastewater & excreta in
agriculture has a long history.
• Many benefits: reliable nutrients and water source;
reduce chemical fertilizers…
• Wastewater & excreta contain variety of pathogens
(viruses, bacteria, parasites) & chemicals.
• Enteric pathogens is a fundamental public health
consideration (diarrhoea, parasitic diseases).
• These may harm people directly through contact or
ingestion or consume contaminated products.

4. Study aim
To assess the infection risks of diarrhoea-related
pathogens in an environmental sanitation and
agriculture systems in Vietnam.

5.  Area: 331,000 km2
 Population: 91 million
 Rural population: 74%
 Under 5 population: 9%
 Population below poverty line: 14.5%
 Life expectancy: 73 (men) & 77
(women)
Study sites

6. Environmental sanitation & agricultural systems
Use of excreta as fertilizer: 51%
Inhabitants: 16,200
Households: 4,300
Single vault latrine: 56%Raise animals: 84%
Use of Nhue River water: 93%Local ponds: 10%

7. Description of the environmental sanitation and agricultural systems
Composting
(5)
Composting
(5)
Water
source
Water
source
Household (wastes)Household (wastes)
Solid wastesSolid wastesExcreta/
Manures
Excreta/
Manures
FoodFood
Waste waterWaste water
Sewages (2)Sewages (2)
SanitationSanitation
Irrigation system (4)Irrigation system (4)Pond (3)Pond (3) CropCrop
LivestockLivestock
Nhue River (1)Nhue River (1)
Pumping stations
Wastewater from Hanoi City (households, industries, hospitals,..)
LandfillLandfill

8. 3.Exposure Assessment
Size & nature of the population, route, amount and
duration of the exposure
1.Hazard Identification
Describe environment, pathogens, Health effects
2.Dose-response Analysis
Relationships between exposure (dose) &
frequency of infection/illness (response)
4.Risk Characterization
Integrate the information from 3 and 4 to express
public health outcomes, taking into account the
variability and uncertainty of the estimations.
Q M R A
Risk management
Communicatio
Dataacquis

9. October 5, 2015 Monday seminar9
1. Hazard identification - Selection of pathogens
– High concentrations of Giardia, Cryptosporidium in wastewater
– Giardia is a common pathogenic parasite (resistant cyst stage).
– Cryptosporidium oocysts resistant to chlorine, no treatment available.
– Giardia & Cryptosporidium have a low infective dose
No Sampling sites
No. of
samples
Exposure scenarios
Accidental ingestion
(mL water)
Events/year
(1) Nhue River water 36 Harvesting vegetables 10 132
(2) Household sewage 36 Cleaning 10 8
(3) Local pond 36 Fishing (harvesting fish) 100 72
(4) Canal/field 60 Growing rice 10 12
(5) Composted excreta 05 Application of excreta 10 mg 6
Total 173 (Source: Haas et al., 1999)
2. Exposure assessment – Exposure scenarios and accidental ingestion

10. October 5, 2015 Monday seminar10
3. Dose-response models (Sources: Haas et al., 1999, Howard et al., 2006)
Estimated single risks of infection
Exponential model (Giardia & Cryptosporidium)
Pinf(d) = 1 – exp(-rd)
Where are:
- Pinf(d) : risk of infection in an individual exposed to a single pathogen dose (d)
- r: infectivity constants (Giardia: 0.02 and Cryptosporidium: 0.00467)
- d (dose ingested) = μ x m
μ: concentration of organism/100mL
m: amount of water accidental ingested

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4. Risk characterisation (Sources: Haas et al., 1999, Howard et al., 2006)
Estimated annual risks of infection
Pinf/y = 1 – [1- Pinf(d)]n
Estimated annual risk of diarrhoea
Pill = Pinf/y x Pill/inf
Where are:
- Pinf(d) : risk of infection in an individual exposed to a single pathogen dose (d)
- n : number of exposures/year/individual
- Pill/inf : disease/infection ratio: G. Lamblia (0.67) C. Parvum (0.39)
Data analysis: Monte Carlo simulations (10,000 iterations) using the @Risk software
version 5.7 Palisade Corp.

12. Estimated single risks of infection for each pathogen
Exposure scenarios Pathogens
Single risk of infection
Mean 5th
95th
(1) Harvesting vegetables in
Nhue River
G. lamblia 1.4 x 10-2
0.0 4.3 x 10-2
C. parvum 2.7 x 10-3
0.0 8.4 x 10-3
(2) Cleaning household sewage G. lamblia 5.4 x 10-2
2.0 x 10-3
1.6 x 10-1
C. parvum 1.4 x 10-2
4.7 x 10-4
4.3 x 10-2
(3) Fishing in the local ponds G. lamblia 7.1 x 10-2
0.0 2.3 x 10-1
C. parvum 1.0 x 10-2
0.0 3.7 x 10-2
(4) Growing rice G. lamblia 1.9 x 10-2
0.0 5.8 x 10-2
C. parvum 4.7 x 10-4
0.0 1.9 x 10-3
(5) Application of excreta in the
fields
G. lamblia 1.9 x 10-1
1.2 x 10-2
5.1 x 10-1
C. parvum N.A N. A N. A
Results (1)

13. Giardia lamblia
0.62
0.31
0.75
0.19
0.59
0.98
0
0.2
0.4
0.6
0.8
1
Harvesting
vegetables
in Nhue
River
Cleaning
the
household
sewage
Fishing in
the local
ponds
Growing
rice
Application
of excreta
in field
Combined
all
exposures
Annualriskofinfection
5% Mean 95%
Estimated annual risks of infection
In comparison with the acceptable risk of 10-4
(< 1 infection/10,000 pers) set by WHO
Results (2)

14. Cryptosporidium parvum
0.26
0.1
0.39
0
0.6
0
0.2
0.4
0.6
0.8
1
Harvesting
vegetables in
Nhue River
Cleaning
household
sewage
Fishing in the
local ponds
Application of
excrtea in the
fields
Combined all
exposures
Annualriskofinfection
5% Mean 95%
Estimated annual risks of infection
In comparison with the acceptable risk of 10-4
(< 1 infection/10,000 pers) set by WHO
Results (3)

15. Estimated annual risks of diarrhoea
In comparison with the maximal risk of diarrhoea of 10-3
pppy proposed by WHO
Results (4)

16. Conclusions
Wastewater & excreta lead to high infection risks (Giardia &
Cryptosporidium) in the exposed population.
Annual infection & diarrhoeal risks exceeded the acceptable risk levels set
by WHO.
QMRA is useful in formulating an integrated framework for pathogen
management to reduce the infection risks & maximise health protection.
Using One Health approach for a better management of animal wastes
and protection of human and environmental health.

17. Acknowledgement