- Watercress is a popular food in New Zealand and is traditionally served cooked, but is increasingly consumed raw in salads or as a garnish.
- Watercress is harvested from waterways, which exposes it to potential chemical and microbiological contamination.
- Microbiological and heavy metal contamination of watercress and growing waters from eleven streams in the Wellington and Wairarapa regions was investigated.
- All sites showed variable but significant levels of E. coli in both watercress and water samples, indicating potential for enteric waterborne pathogens.
- Campylobacter was detected in the growing waters at all sites, with potential risks of gastrointestinal illness for consumers.
- Excessive heavy metal contamination did not exceed regulations in watercress, but urban sites did have higher levels of heavy metals.
- Based on the findings, watercress harvested from uncontrolled surface water sources should be cooked before consumption.
- Watercress should not be eaten raw unless growing waters are strictly controlled and monitored.
- People gathering watercress may be at risk of waterborne illnesses.
- Watercress grown in water subject to heavy metal contamination may bio-accumulate heavy metals to levels exceeding health guidelines.
1. Watercress sampling was conducted over a five-week period to assess variability in contaminant concentrations.
2. Healthy watercress samples were randomly selected from each site for analysis.
3. Watercress species were identified at each site by sending seedheads and flowers to an expert.
4. Microbiological testing of watercress and growing waters included bacterial counts for E. coli, fecal coliforms, and total coliforms, as well as presence/absence tests for Campylobacter species.
5. E. coli is the preferred indicator organism for testing water quality as it indicates recent fecal contamination.
6. Campylobacter is a common food and waterborne pathogen in New Zealand.
7. Microbiological analyses were conducted by an accredited IANZ laboratory.
8. Laboratory analysis methods included microbiological testing for E. coli and Campylobacter species in watercress and water samples.
9. Confirmation tests were conducted for E. coli using EMB agar plates, BGBB, and Indole production.
10. Campylobacter species were confirmed through Gram stain, catalase, and oxidase tests.
Campylobacter was found in 80% of water samples and 11% of watercress samples, making all sites unsuitable for watercress consumption without boiling
- Campylobacter is excreted in the feces of mammals and birds, indicating widespread distribution in all catchment types
- E. coli contamination was present in all watercress and growing water samples, with high levels in most sites except the Golf course site
- Faecal contamination on watercress poses a risk of human pathogen presence and infection
- Giardia, Cryptosporidium, and other protozoan pathogens are widespread in New Zealand surface waters and can be transmitted to humans via water
- Viruses such as Adenoviruses, Enteroviruses, Rotaviruses, and Norwalk viruses can cause various diseases and can be transmitted via polluted water
No known enteric disease outbreaks linked to watercress consumption in New Zealand
- Overseas outbreaks linked to contaminated fresh vegetables, watercress included
- Thorough washing and treatment with chlorinated water can reduce but not eliminate pathogens on produce
- Water quality controls during harvesting, processing, and distribution are crucial in reducing health risks
- Liver flukes (Fasciola hepatica) can be transmitted through watercress consumption
- Potential for heavy metal contamination in watercress grown in certain areas of New Zealand
- Contact with contaminated water while gathering watercress can pose health risks, especially for high-risk groups
1. Watercress harvested from any uncontrolled surface water source in New Zealand should not be consumed unless thoroughly cooked to destroy potential pathogens.
2. Watercress should not be eaten raw unless the growing environment is strictly controlled and monitored to ensure water quality.
3. Further research is needed to assess the risk of waterborne illnesses from gathering watercress from uncontrolled surface waters.
4. Study on the potential for fascioliasis in New Zealand from consuming wild watercress is recommended.
5. Avoid consuming watercress from areas with high levels of arsenic, such as in the central North Island.
6. Watercress should not be gathered for consumption from waterways with significant industrial discharges.
from the above information, 1.what are the findings, 2. what are the gaps for future research to be carried out 3. where do study conducted 4.
1. The findings of the study include:
- High levels of E. coli were found in watercress and growing waters at all sites, indicating potential for enteric waterborne pathogens.
- Campylobacter was detected in the growing waters at all sites, posing risks of gastrointestinal illness for consumers.
- Excessive heavy metal contamination did not exceed regulations in watercress, but urban sites had higher levels of heavy metals.
- Watercress harvested from uncontrolled surface water sources should be cooked before consumption to reduce risks of waterborne illnesses.
- Watercress should not be eaten raw unless growing waters are strictly controlled.
2. Gaps for future research to be carried out include:
- Further research is needed to assess the risk of waterborne illnesses from gathering watercress from uncontrolled surface waters.
- Study on the potential for fascioliasis in New Zealand from consuming wild watercress is recommended.
- More research on heavy metal contamination in watercress grown in different areas of New Zealand is needed.
- Investigations into other potential pathogens such as Giardia, Cryptosporidium, and viruses in watercress are needed.
3. The study was conducted in the Wellington and Wairarapa regions of New Zealand, specifically from eleven streams in those areas.
4. The study highlights the importance of water quality controls during harvesting, processing, and distribution of watercress to reduce health risks for consumers. It also emphasizes the risks associated with harvesting watercress from uncontrolled surface water sources, especially in areas with potential heavy metal contamination. It suggests that future research should focus on assessing and mitigating these risks to ensure the safety of watercress consumption.