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One Health Perspective And Assessment Of Giardia & Cryptosporidium Infections Phuc PHAM-DUC

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

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One Health Perspective And Assessment Of Giardia & Cryptosporidium Infections Phuc PHAM-DUC

  1. 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. 2. Contents • Introduction • Study aim • Study sites • Methods • Results • Conclusions • Acknowledgement
  3. 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. 4. Study aim To assess the infection risks of diarrhoea-related pathogens in an environmental sanitation and agriculture systems in Vietnam.
  5. 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. 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. 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. 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. 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. 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
  11. 11. October 5, 2015 Monday seminar11 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. 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. 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. 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. 15. Estimated annual risks of diarrhoea In comparison with the maximal risk of diarrhoea of 10-3 pppy proposed by WHO Results (4)
  16. 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. 17. Acknowledgement

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