EFSA panel addresses risk of Salmonella and Norovirus in tomatoes

Epidemiological data from the EU have identified one salmonellosis and one Norovirus outbreak associated with tomato consumption between 2007 and 2012.

The European Commission asked EFSA‘s Panel on Biological Hazards (BIOHAZ Panel) for a scientific Opinion on the health risk posed by pathogens that may contaminate food of non-animal origin (FoNAO).

It is the fourth opinion of five and addresses the risk from Salmonella and Norovirus in tomatoes.​

The panel made seven recommendations including ISO technical specifications for Norovirus detection and quantification on tomatoes should be further refined, more detailed categorization of food of non-animal origin should be introduced and there should be implementation and evaluation of procedures to verify agricultural and hygiene practices for tomatoes.

Processes at primary production which wet tomatoes represent the highest risk of contamination, including spray application of agricultural chemicals and the use of overhead irrigation.

Salmonella risk factors​

The main risk factors for Salmonella and Norovirus in tomatoes, including agricultural production systems, origin and further processing are poorly documented but BIOHAZ provided examples of what they could include for Salmonella.

Environmental factors that increase the transfer of pathogens from animal reservoirs to the tomato plants; contact with animal reservoirs gaining access to tomato growing areas and use of untreated or insufficiently treated organic amendments were identified.

Others were use of contaminated water for irrigation or application of agricultural chemicals such as pesticides, and contamination or cross-contamination by harvesters, food handlers and equipment at harvest or post-harvest.

The ability of Salmonella to survive on or in tomatoes is cultivar dependent and the growth stage of the plant represents an important factor for internalization through the root system, suggesting that plants are more susceptible to internalization immediately after transplantation.

For Salmonella, the risk of cross-contamination during washing (whenever applied), is reduced if disinfectants are properly used within the washing tank.

Norovirus assessment​

For norovirus the risk factors are also poorly documented but are likely to include things based on what is known for other pathogens or other fresh produce.

Environmental factors such as heavy rainfall that increase the transfer of Norovirus from sewage or sewage effluents to irrigation water sources or tomato growing areas;  use of sewage contaminated water for irrigation or application of agricultural chemicals such as pesticides, and contamination and cross-contamination by harvesters, food handlers and equipment at harvest or post-harvest.

No information is available on the potential for Norovirus to internalise within, or survive on, tomatoes, said the panel.

The effectiveness of disinfectants against Norovirus is not fully defined due to the lack of an infectivity assay.

Mitigation options​

The BIOHAZ Panel also looked at possible specific mitigation options and assessed their effectiveness and efficiency to reduce the risk posed by Salmonella and Norovirus in tomatoes.

“Attention should be paid to the selection of the water source for irrigation, agricultural chemical application (e.g. pesticides and fungicides) and in particular avoiding the use or the ingress of sewage contaminated water,” ​said the panel.

“​Among the potential interventions, both efficient drainage systems that take up excess overflows and water treatment are needed to prevent the additional dissemination of contaminated water.​

“All persons involved in the handling of tomatoes should receive hygiene training appropriate to their tasks and receive periodic assessment while performing their duties to ensure tasks are being completed with due regard to good hygiene and hygienic practices.”​

On recommending microbiological criteria for the pathogens in tomatoes in the production chain, the panel said there is no routine or regular monitoring of tomatoes in EU Member States and there is very limited data on their occurrence in/on tomatoes in Europe.