Microbiological quality of water spinach grown in the Boeng Cheung Ek lake in Phnom Penh and in peri-urban aquatic

systems in Hanoi

Vuong Tuan Anh1, Lise Tønner Klank2, Phung Dac Cam1, Anders Dalsgaard2.

1Division of Enteric Infection Diseases, National Institute of Hygiene and Epidemiology, Vietnam; 2Department of Pathobiology, Royal Veterinary and Agricultural University, Denmark

Study objectives

1. To determine the numbers of thermotolerant coliforms, helminth eggs and protozoan parasites in water spinach grown in Boeng Cheung Ek (BCE) lake, Phnom Penh and at two peri-urban communes in Hanoi, including samples harvested with and without wastewater (ww) exposure

2. To assess the association between microbiological water quality and of water spinach

Sites and methodology

Sampling sites and schedule

Phnom Penh: 2 inlets, 1 outlet of BCE lake and the control site (a small pond); all sites sampled four times; with and without ww exposure of plants

Hanoi: one ww-irrigated site, one rainwater-irrigated site, 6 fields at each site sampled during wet and dry seasons (duplicate samples)

Number of sample collected: 68 plant samples in Phnom Penh; 216 plant samples in Hanoi

Sites and methodology

Parameters: thermotolerant coliforms, E. coli, helminth eggs (Ascaris lumbricoides, Trichuris trichiura, hookworm) and protozoa (Giardia intestinales, Cryptosporidium parvum and Cyclospora spp.)

Sample analysis: Cambodian Pasteur Institute and NIHE

Laboratory methods: MPN for thermotolerant coliforms and helminth egg enumeration according to WHO manual 1996, Immuno-flourescent microscopy to detect protozoan parasites

Phnom Penh results: Numbers of thermotolerant coliforms and E. coli in water spinach

6181818N =

location of sampling

controlSteung ChrovTrabekJICA

ther

mot

oler

ant c

olifo

rms

10

8

6

4

239

2184N =

location of sampling

controlSteung ChrovTrabekJICA

E.co

li lo

g

7

6

5

4

3

2

1

0

Phnom Penh: protozoan parasites in water spinach (total 68 samples)

0

2

4

6

8

10

12

JICA Trabek Steung Chrov Control

Nu

mb

er

of

po

sit

ive

sa

mp

les

Cyclospora Cryptosporidium Giardia

Phnom Penh: helminth eggs qualitative analysis

Sampling location

Hook-worm

Ascaris spp.

Trichuris spp.

JICA1 0/12 0/12 0/12

Trabek1 0/12 1/12 0/12

Steung Chrov2 1/12 2/12 0/12

Control 0/8 1/8 0/8

1 inlet; 2 outlet

Phnom Penh: nos of thermotolerant coliforms in water spinach exposed versus non-exposed to ww during harvest

3999 3999N =

location of sampling

ControlSteung ChrovTrabekJICA

the

rmo

tole

ran

t co

lifo

rms

log

10

8

6

4

2

un-exposure of w ater

exposure of w ater

14

21

13

Correlation of microbiological quality of water and water spinach

25252525 6181818N =

location of sampling

Control (veg)

Steung Chrov

Trabek

JICA

control (w ater)

the

rmo

tole

ran

t co

lifo

rms

log

10

8

6

4

2

w ater spinach

w ater

90

9486

73117

77

81

39

Hanoi results: Thermotolerant coliforms in water spinach (log MPN/g)

1,00E+00

1,00E+01

1,00E+02

1,00E+03

1,00E+04

1,00E+05

WW-wet season WW-dry season Non-WW-wet season Non-WW-dry season

A=harvested by NIHE B=harvested by farmer, no postharvest washing C=harvested by farmer, plus postharvest washing

BL=after storage overnight, before leaving for market D=upon arrival to market

Hanoi results: Seasonal occurrence of protozoan parasites in ww-irrigated and rainwater-irrigated water spinach (%) (total of 216 samples) in peri-urban Hanoi

6.7

3.3

18.8

45.8

10.0

11.9

6.3

33.3

6.7

11.9

2.1

6.3

0

5

10

15

20

25

30

35

40

45

50

WW-April-May WW-Nov-Dec Non-WW-April-May Non-WW-Nov-Dec

%

Cyclospora

Giardia

Cryptosporidium

Hanoi results: helminth egg qualitative analysis

Sampling location

Hook-worm

Ascaris spp.

Trichuris spp.

WW-irrigated site – Wet

season (n=48) 0/48 1/48 0/48WW-irrigated site – Dry

season (n=48) 0/48 2/48 0/48Non-WW-irrigated site –

Wet season (n=60) 0/60 0/60 0/60Non-WW-irrigated site –

Wet season (n=60) 0/60 0/60 0/60

Phnom Penh study – Conclusions

• Thermotolerant coliforms– Relatively higher levels (105-106 /g) on water

spinach• Protozoan parasites

– Giardia is most prevalent, particularly in plant samples collected at inlets

• Helminth eggs– Very low levels detected at all sampling sites

Hanoi study – Conclusions

• Thermotolerant coliforms– Relatively low levels on water spinach (<104/g)– No apparent differences between seasons

• Protozoan parasites– Higher prevalences during dry season at WW-site– Giardia is most prevalent, particularly at WW-site– Cryptosporidium: high levels during dry season at WW-site– Cyclospora is less prevalent than Giardia and

Cryptosporidium, but is present at both sites and during both seasons

• Helminth eggs– Very low levels detected at both sites, no apparent

difference between seasons

Study completion and remaining work

• Data analysis

• PCR analysis for identification and characterization puruposes; and subtyping of protozoans

• Preparation and submission of manuscripts (1-2 MS)

Acknowledgements

• Staff of the Faculty of Fisheries, at the Royal University of Agriculture, in particular Chouk Borin, and at the Pasteur Institute in Phnom Penh for excellent technical assistance in sample and data collection

• The National Inst of Hygiene and Epidemiology (NIHE) for providing laboratory facilities and good laboratory support for sample analyses

• EU-INCO-DEV (PAPUSSA), DANIDA (grant no. 104.Dan.8.L ”Sanitary Aspects of Drinking Water and Wastewater Reuse in Vietnam”) and KVL for financial support