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  1. Sampling to Protect the Food Supply

Microbiological Surveillance Sampling: FY17-21 Fresh Herbs (Cilantro, Basil & Parsley) Assignment

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Cilantro, Basil & Parsley

In 2017, the U.S. Food and Drug Administration (FDA) initiated a sampling assignment to collect fresh cilantro, parsley, and basil. The samples collected were tested for Cyclospora cayetanensis, Salmonella spp., and Shiga toxin-producing Escherichia coli (STEC). The assignment aimed to estimate the prevalence of these pathogens in the three types of fresh herbs and to take follow-up actions in the case of pathogen findings, as warranted. The agency also sought to identify common factors, such as origin, among the pathogens’ findings.

The FDA implemented this sampling assignment in September 2017, anticipating that it would take about two years to complete. However, due to the COVID-19 pandemic, the FDA paused its sampling of fresh herbs in the spring of 2020. The sampling resumed in January 2021 and the collection and testing of samples concluded in September 2021.

The FDA collected fresh raw basil, cilantro, and parsley samples from various points in the distribution chain. Imported fresh herbs were collected at ports of entry, importer warehouses, and other storage facilities. Domestic samples were collected at packinghouses, distribution facilities, wholesalers, and retail locations. Agency field staff collected retail samples from refrigerated storage at grocery stores, prior to consumer handling.

The FDA detected C. cayetanensis in 11 of the 120 basil samples, 7 of the 553 cilantro samples, and none of the 139 parsley samples, an estimated prevalence of 9.2% for basil, 1.3% for cilantro, and 0% for parsley. The agency detected Salmonella spp. in 7 of the 248 basil samples, 8 of the 849 cilantro samples, and 2 of the 261 parsley samples, an estimated prevalence of 2.8% for basil, 0.9% for cilantro, and 0.8% for parsley. The FDA detected STEC in none of the 242 basil samples, 1 in 849 cilantro samples, and none of the 259 parsley samples, an estimated prevalence of 0% for basil, 0.1% for cilantro, 0% for parsley.

Upon detecting a positive sample, the FDA notified the responsible firm with respect to the test results and worked with its owners or management to take appropriate action to safeguard public health. Follow-up activities included measures to correct and prevent contamination and, where applicable, remove violative food from the market.

As to the domestic samples that tested positive for a target pathogen, the agency worked with each firm that owned or distributed the adulterated herbs to effect four voluntary product recalls. With respect to the import samples that tested positive for a target pathogen, the FDA refused to admit 20 shipments associated with positive findings into the U.S. and placed the responsible firms and product on Import Alert 99-23 and/or Import Alert 99-35, thereby requiring additional controls for future entries.

The findings of this assignment affirm that pathogens may be present in fresh basil, cilantro, and parsley and so underscore the need for food safety prevention measures. The FDA encourages industry to ensure its compliance with the agency’s Produce Safety Rule, Preventive Controls for Human Food Rule, and FSMA Final Rule on Requirements for Additional Traceability Records for Certain Foods, as applicable. Similarly, importers of these foods should ensure their compliance with the FDA’s Foreign Supplier Verification Programs Rule.

Generally, fresh basil, cilantro, and parsley eaten in the U.S. are safe to consume without known contamination with microbial hazards. However, these and other fresh herbs may not undergo a ‘kill step’ prior to consumption, to reduce or eliminate microbial hazards, if present. Consumers can take simple steps to minimize possible risks associated with eating fresh herbs. The FDA recommends that consumers store perishable vegetables like herbs in a clean refrigerator at a temperature of 40°F or below and wash all produce thoroughly under running water before preparing and/or eating. For all fresh produce, diligence in safe handling practices is essential. The FDA has published guidance for industry that advises maintaining sanitary conditions on food contact surfaces and ensuring that temperatures promoting optimum quality are upheld. These measures reduce the risk of microbial hazards and safeguard produce against pathogens.

At-A-Glance

  • The assignment objectives were to:
    • Estimate the prevalence of Cyclospora cayetanensis, Salmonella spp., and Shiga toxin-producing Escherichia coli (STEC) in basil, cilantro, and parsley;
    • Take appropriate follow-up action in response to pathogen findings; and
    • Determine if there were common factors associated with pathogen findings, such as by origin, when possible.
  • The FDA collected and tested 1,383 samples of fresh herbs during the assignment, which was conducted from September 2017 to September 2021.
  • Salmonella spp. findings: The FDA detected Salmonella spp. in 17 samples out of 1,358 domestic and imported samples collected and tested.
  • C. cayetanensis findings: The agency detected C. cayetanensis in 18 samples out of 812 domestic and imported samples collected and tested.
  • STEC findings: The agency detected STEC in one (1) domestic sample out of 1,350 samples collected and tested.
  • Given the findings of the assignment, the FDA encourages industry to ensure its compliance with the agency’s Produce Safety Rule, Preventive Controls for Human Food Rule, and Food Safety Modernization Act (FSMA) Final Rule on Requirements for Additional Traceability Records for Certain Foods. Importers of fresh herbs should ensure their compliance with the agency’s Foreign Supplier Verification Programs Rule.
  • This assignment was the agency’s first largescale field activity to focus on fresh basil, cilantro, and parsley. It provided the FDA with baseline data (i.e., its first prevalence estimates) of C. cayetanensis, Salmonella spp., and STEC in the three commodities.

Background

In 2011, the FDA Food Safety Modernization Act (FSMA) amended the Federal Food, Drug, and Cosmetic Act (FD&C Act) to provide the agency with additional authority to better prevent food safety problems before they occur. To develop better prevention-based systems, the FDA needs data and other information to help identify hazards that must be addressed and minimized. That is why sampling is an important part of informing the agency’s preventive approach to food safety. To achieve this, in 2013 the agency updated its sampling strategy, focusing on collecting larger sets of samples like those in this study. This shift aimed to better determine the prevalence of contamination, identify common contributing factors, such as origin, and implement measures to prevent contamination by pathogens.

Objectives

The objectives of the FDA’s FY 2017-2021 Fresh Herbs Assignment were:

  • To estimate the prevalence of Salmonella spp., Cyclospora cayetanensis, and Shiga toxin-producing Escherichia coli (STEC) in fresh basil, cilantro, and parsley;
  • To determine if there were common factors associated with positive findings (such as by origin) when possible; and
  • To take appropriate follow-up action in response to contamination findings.

Sample Collection

The FDA originally planned to collect and test 1,600 samples of basil, cilantro, and parsley, a sample size consistent with the design of the agency’s large-scale microbiological surveillance sampling assignments. The agency further planned to collect and test comparable numbers of domestic and import samples (i.e., roughly half of each). In July 2018, the FDA also began collecting fresh herb samples for Cyclospora cayetanensis given that Cyclospora-related illnesses typically occur during the summer.

Following the assignment’s implementation, unforeseen circumstances prompted the agency to reduce its collection target and extend its anticipated completion timeline from 2019 to 2021. Several months into the assignment, the FDA identified a need to make slight adjustments to avoid biasing its dataset by oversampling product from the same firms and to minimize the burden on industry. Specifically, in March of 2019, the FDA lowered its collection target slightly to account for a 35-day lapse in federal appropriations that began on December 22, 2018, and the associated impact on the workload of the agency field staff. Also, in March of 2020, the FDA paused its fresh herbs sampling for nine months in light of the coronavirus (COVID-19) pandemic.

The FDA resumed its fresh herbs sampling in January 2021 after re-assessing and adjusting its collection target to ensure that the agency would achieve the public health goals of the assignment while bringing it to a conclusion. The FDA completed its collection and testing in September 2021, having obtained 1,383 samples in all.

Pathogen Findings

This section reports the findings of Cyclospora cayetanensis, Salmonella spp., and STEC in the samples tested, and breakdowns by season, origin, and ‘repeat violation’ firms. The test methods the FDA used are described in Appendix A.

The binning of the test data by individual commodity and analyte reduces each category’s sample size in relation to the full dataset and thus yields a relatively wide confidence interval for some of the prevalence estimates, as shown in the tables below.

Regulatory Approach

The Federal Food, Drug, and Cosmetic Act (FD&C Act) authorizes the FDA to take regulatory action regarding adulterated food. Regulatory tools at the agency’s disposal include warning letters, import alerts, import refusals, administrative detentions, seizures, injunctions, suspension of registration, and mandatory recalls (if a firm does not conduct an adequate voluntary recall).

Basil, cilantro, and parsley that test positive for Salmonella spp. and Escherichia coli are adulterated under Section 402(a)(1) of the FD&C Act in that they bear or contain a poisonous or deleterious substance which may render them injurious to health.

Fresh herbs that test positive for Cyclospora cayetanensis are adulterated under Section 402(a)(4) of the FD&C Act in that such article has been prepared, packed, or held under insanitary conditions whereby it may have been rendered injurious to health. Such foods may be subject to regulatory action.

Public Health Impact and Follow-Up Activities

The agency analyzed the Salmonella spp. and STEC detected in fresh basil, cilantro, and parsley samples to identify their genetic patterns and determined whether those pathogens may be linked to human illness. The isolates from twelve of the fresh herb samples obtained by the FDA were a genetic match to clinical isolates, but there was no epidemiological evidence that the product corresponding to the samples were the source of illness.

Whenever the FDA detected a positive finding under this assignment, the agency sought to remove all affected product from the marketplace. Removal of contaminated products from the marketplace prevents consumption and thus avoids potential illnesses, consistent with the agency’s prevention and response efforts outlined in the Cyclospora Prevention, Response and Research Action Plan.

With respect to the domestic samples that tested positive for a target pathogen, the agency worked with the firm that owned or distributed the affected product, which resulted in four distinct firms conducting voluntary product recalls. In some cases, however, there was no product left to recall, or low likelihood of availability of product to recall, because of the commodity’s relatively short shelf life. In cases where no recall was carried out, the agency provided the firm with its test results, advised the firm to take steps to prevent contamination along with its responsibility to reduce microbial hazards, and to address gaps in good agricultural practices.

Additionally, because the intestinal illness cyclosporiasis only occurs in humans, findings of Cyclospora cayetanensis on produce suggest that the food may have come into contact with sources of human waste. That being the case, the FDA conducted follow-up inspections at four domestic farms corresponding to findings of the parasite in domestic basil and cilantro samples to determine potential sources and routes of contamination. The on-farm investigations sought to help farm management identify microbial risks so they could improve the microbiological safety of their operation(s) and potentially prevent contaminated product from reaching consumers.

The FDA conducted follow-up inspections at two Hawaiian farms for positive findings of C. cayetanensis in basil. Further sampling did not detect any pathogens at the first farm. The FDA notified farm management of the findings and provided guidance on best practices to reduce potential sources and routes of microbial contamination. Additionally, farm management implemented corrective actions to improve worker health and hygiene. At the second Hawaiian farm, management voluntarily committed to suspending growing operations because of the positive finding of C. cayetanensis in basil until they completed their investigation to identify the source(s) of contamination.

Upon identifying C. cayetanensis in cilantro samples collected during the inspections from a farm in California and another in Oregon, the FDA notified both farms about the positive samples. The farms initiated recalls of the product associated with the positive findings. The FDA’s follow-up inspections revealed that employees at both farms were not implementing adequate sanitation practices to reduce microbial hazards related to equipment and handwashing. For example, at the Oregon farm, workers were observed harvesting cilantro without proper handwashing after using the latrine. Despite the risk of contamination from unwashed hands, no illnesses were known to be associated with cilantro from that farm.

With respect to the import samples that tested positive for a target pathogen, the FDA refused to admit the 20 shipments associated with the positive findings into the U.S. and placed 13 responsible firms and product on Import Alert 99-23 and/or 99-35, thereby requiring additional controls for future entries. For those products to be admitted into the U.S., the company is required to provide evidence to the FDA to overcome the appearance of a violation, such as the test results of a third-party laboratory, verifying that the product does not contain the specific pathogen identified on the import alert. When the criteria to place a firm on import alert were not met, the agency carried out intensified sampling (i.e., additional sampling) of fresh basil, cilantro, or parsley from the responsible firms. The chart below (Figure 1) reports the follow-up action(s) taken in response to all the positives.

Figure 1 : Follow-Up Actions by Type

Follow-Up Actions by Type

Conclusion

This assignment was successful in addressing its three strategic objectives: to estimate the prevalence of Cyclospora cayetanensis, Salmonella spp., and Shiga toxin-producing Escherichia coli (STEC) in fresh basil, cilantro, and parsley; to determine if there were common factors associated with positive findings (such as by origin) when possible; and to take appropriate follow-up action in response to contamination findings.

Based on the assignment findings, the agency estimated the prevalence of C. cayetanensis, Salmonella spp., and STEC in fresh basil, cilantro, and parsley as follows:

  1. Cyclospora cayetanensis. The prevalence of C. cayetanensis was estimated to be 9.2% with a 95% confidence interval of 4.4% to 16.5% for basil, 1.3% with a 95% confidence interval of 0.5% to 2.6% for cilantro, and 0% with a 95% confidence interval of 0% to 2.6% for parsley.

  2. Salmonella spp. The prevalence of Salmonella spp. was estimated to be 2.8% with a 95% confidence interval of 1.1% to 5.7% for basil, 0.9% with a 95% confidence interval of 0.4% to 1.9% for cilantro, and 0.8% with a 95% confidence interval of 0.1% to 2.7% for parsley.

  3. STEC. The prevalence of STEC was estimated to be 0% with a 95% confidence interval of 0% to 1.5% for basil, 0.1% with a 95% confidence interval of 0.003% to 0.7% for cilantro, and 0% with a 95% confidence interval of 0% to 1.4% for parsley.

The prevalence estimates in this report are provided for informational purposes. The estimates of prevalence in this report may be biased due to (1) the samples collected may not represent the population at the time of sample collection (2) the estimates are unweighted, and some groups (e.g., domestic or imported) of products might have been over- or under-sampled. Therefore, the FDA cautions against making inference more broadly about the contamination or potential for contamination of fresh herbs based solely on this assignment’s findings.

Additionally, the agency evaluated the findings for common factors for seasonality and product origin. While this assignment was designed primarily to estimate the prevalence of the target pathogens associated with fresh herbs, the agency evaluated its test results preliminarily and throughout its sampling for signals (i.e., variations in prevalence by origin and season) to determine whether more targeted sampling or further study was warranted, the details of which can be found in Appendix B and C. The agency did not detect any signals related to origin or season that warranted more targeted sampling or additional study. The FDA also calculated and has provided the breakdowns for season and origin.

Lastly, FDA took appropriate follow-up actions, or worked with the responsible firms to do so, in response to all pathogen findings. The follow-up actions included voluntary recalls and placement of firms on import alert.

Next Steps

The assignment findings may help the agency to update program priorities, including future sampling assignments and the prioritization of surveillance inspections. The FDA will continue to sample fresh herbs for pathogens as warranted, consistent with its mission to protect consumers. Future next steps may include designing an assignment specifically aimed at assessing whether seasonality impacts contamination rates. The findings suggest the potential for contamination with C. cayetanensis is not restricted to the summer months.

In 2019, the FDA established a task force dedicated to C. cayetanensis. The task force developed the Cyclospora Prevention, Response and Research Action Plan, a multi-year strategic plan to improve prevention, enhance response activities, and fill knowledge gaps. The assignment was able to fill the knowledge gap about the prevalence of C. cayetanensis on fresh basil, cilantro, and parsley. The response was enhanced by timely follow-up actions during the assignment. As a result of this assignment, industry collaboration continues to grow as outreach on prevention measures is shared with our domestic and international regulatory partners, to include FDA’s regulatory counterparts in Latin America. Additionally, the agency developed and is validating in multiple FDA laboratories an improved method[9] to detect C. cayetanensis in produce.  

The assignment data affirm that C. cayetanensis, Salmonella spp., and STEC may be present in fresh basil, cilantro, and parsley. This underscores the need for growers, processors, and others in the fresh herbs supply chain to comply with the agency’s draft guidance on the Produce Safety Rule, Preventive Controls for Human Food Rule, and FSMA Final Rule on Requirements for Additional Traceability Records for Certain Foods, as applicable. For importers of fresh herbs, compliance with the agency’s Foreign Supplier Verification Programs (FSVP) Rule is an important way to help ensure the safety of imported fresh basil, cilantro, and parsley.

Generally, fresh basil, cilantro, and parsley eaten in the U.S. are safe to consume without known contamination with microbial hazards. However, these and other fresh herbs may not undergo a ‘kill step’ prior to consumption. Consumers can take simple steps to reduce any possible microbial risks related to the consumption of fresh herbs. The FDA recommends that consumers store perishable vegetables like herbs in a clean refrigerator at a temperature of 40°F or below and wash all produce thoroughly under running water before preparing and/or eating. For all fresh produce, diligence in safe handling practices is essential. The FDA has published guidance for industry that advises maintaining sanitary conditions on food contact surfaces and ensuring that temperatures promoting optimum quality are upheld. These measures reduce the risk of microbial hazards and safeguard produce against pathogens.

Appendix A: Test Methods

Analysts tested the samples using aseptic methods specific to each pathogen, as follows:

Appendix B: Pathogen Findings by Season

The following table categorizes the pathogen findings by season. The seasons were broken down according to the Earth's Seasons - Equinoxes, Solstices, Perihelion, and Aphelion.

Appendix C: Pathogen Findings by Origin

Pathogen

Country of origin

No. of Samples Collected & Analyzed

No. of Sample Positive

Estimated prevalence

95% Confidence Interval
Lower Limit

95% Confidence Interval
Upper Limita

C. cayetanensis

U.S.

412

4

0.97%

0.27%

2.47%

C. cayetanensis

Mexico

328

7

2.13%

0.75%

4.73%

C. cayetanensis

Other

72

7

9.72%

4.00%a

19.01%a

Salmonella spp.

U.S.

712

6

0.84%

0.31%

1.83%

Salmonella spp.

Mexico

549

8

1.46%

0.63%

2.85%

Salmonella spp.

Other

97

3

3.09%

0.64%a

8.77%a

STEC

U.S.

709

1

0.14%

0.004%

0.78%

STEC

Mexico

545

0

0%

0%

0.67%

STEC

Other

96

0

0%

0%

3.77%

a The wide range of 95% confidence interval reflects a high level of uncertainty caused by a small sample size.

Pathogen

Origin

Number of Samples Collected and Analyzed

Number of Test Positive Samples

Estimated  prevalence

95% Confidence Interval
Lower Limit

95% Confidence Interval
Upper Limit

C. cayetanensis

Domestic

412

4

0.97%

0.27%

2.47%

C. cayetanensis

Imported

400

14

3.50%

1.87%

5.94%

Salmonella spp.

Domestic

712

6

0.84%

0.31%

1.83%

Salmonella spp.

Imported

646

11

1.70%

0.85%

3.03%

STEC

Domestic

709

1

0.14%

0.004%

0.78%

STEC

Imported

641

0

0%

0%

0.57%

[1] U.S. Food and Drug Administration (FDA). (2023). Fresh herbs outbreak data. Center for Outbreak Response and Evaluation.

[2] U.S. Food and Drug Administration (FDA). (2019). Public Health Advisories from Investigations of Foodborne Illness Outbreaks | FDA

[3] Davis, J. (Reviewed 2022). Fresh herb production and marketing. Department of Horticultural Science, NC State University.

[4] Blue Book Services. (2024). Cilantro market summary.

[5] Blue Book Services. (2024). Parsley market summary.

[6] Singh, S. (2021). Fresh Herbs Market Research Report Information. https://www.marketresearchfuture.com/reports/fresh-herbs-market-8789.

[7] Bardsley, C.; Boyer, R.; Rideout, S.; Strawn, L. (2019). Survival of Listeria monocytogenes on the surface of basil, cilantro, dill, and parsley plants. Food Control, Vol. 95, Jan. 2019, p. 90-94.

[8] Centers for Disease Control and Prevention. Countries or Regions at Risk for Cyclosporiasis | Cyclosporiasis | CDC

[9] Molecular Detection of Cyclospora cayetanensis in Fresh Produce Using Real-Time PCR January 2024

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