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Could the ongoing Salmonella outbreak have been prevented?

Opinion

Outbreaks of Salmonella and other pathogens in fresh produce are unfortunately relatively frequent occurrences. This is true, particularly with imported Mexican papaya.

Neither the Food and Drug Administration nor the Centers for Disease Control have disclosed potential root cause in the latest outbreak, however, the factors that lead to contamination of produce are well known.

Just as in an operation with previous sanitation or food safety failures, food industries as a whole with unsafe track records need to collectively correct deficiencies on an industry-wide basis. The tomato industry in Florida has adopted the Tomato GAP — Florida T-GAP — rule in response to tomato-borne Salmonella outbreaks. This example of an industry-wide program has proven to be successful. There have been no nationwide outbreaks of Salmonella in Florida grown tomatoes during the past few years.

For the papaya industry to take similar effective corrective actions, the root cause of microbial contamination of papaya must be determined.

We can examine three categories of risk:

  1. Animal intrusion, or animal fecal matter;
  2. Human to food transmission through fecal matter and sewage; and
  3. Unsafe applications of water aka the three W’s — workers, water, and wildlife.

Papaya is a tree fruit that grows on a palm-like tree, about 10-15 feet off the ground. Irrigation water is usually applied by the drip method, where only the shallow roots receive water. Water also is sometimes used to dilute and apply crop protection chemicals such as a pesticide.

While water from unsafe sources is a known Salmonella risk, trees provide a convenient location for birds, and avian activity is a logical assumption as the root source of papaya contamination.

The recent report by FDA that three separate outbreak strains of Salmonella have been detected in papaya from one farm, is somewhat confounding and makes developing a theory difficult. Salmonella is carried by birds, and sometimes entire flocks or populations can be infected. However, avian infections involving several strains simultaneously might mean separate exposures of Salmonella in the environment, which conceivably may occur in a region with notoriously poor environmental sanitation.

Humans can be infected with Salmonella and spread the infection to papaya during harvesting. Subsequently, tools, containers, vehicles, and facilities used to handle and pack the fruit can become contaminated, furthering the spread of the pathogen. Again, three separate strains at work simultaneously in the harvester workforce is hard to comprehend.

Outbreaks with multiple strains of pathogens occur, but this is not typical of foodborne illness outbreaks, which are often traced to a common source of a single agent. When multiple agents are involved, the vehicle is often sewage. Human sewage is highly infectious and could contain not just several strains of a pathogen, but multiple pathogens, such as Enterohemorrhagic E. coli and Salmonella.

Exposure to sewage can occur when septic systems or treatment plants fail. Flooding or excessive rainfall can increase the risk of environmental transmission of pathogens to fruit. Soil can be carried to harvested fruit by multiple vehicles in the harvest operations, so a soil-borne or surface water exposure route is not out of the question.

Packing operations that receive and pack contaminated papaya can serve as a means of cross-contamination. If packing equipment or a facility’s environment become soiled, Salmonella can spread over time and establish environmental niches with the production environment then serving as the reservoir of the agent. Being a consolidation point, contaminated packinghouse work surfaces can contaminate large amounts of otherwise safe fruit.

We expect and hope that FDA and CDC will get to the bottom of what happened, and make the information public so the papaya industry can prevent future occurrences.

While the problem of microbial contamination of fresh fruits and vegetables is a difficult problem — fresh produce is the leading category of commodities involved in foodborne illness outbreaks — a properly developed risk-based food safety plan should minimize the risk of large-scale and ongoing outbreaks. A coordinated effort to adopt Good Agricultural Practices, specific to the papaya industry, is needed.

In the meantime, there is a risk assessment document available to tree fruit producers. The standards in it are based on the reasonably foreseeable and known risks related to growing and harvesting tree crops. The Produce Safety Alliance (PSA) at Cornell University recommends that growers of fresh produce develop a food safety plan. Completing a risk assessment is a good starting point, but the implementation of a plan’s policies and procedures takes management commitment and work.

Given the diverse risks in fresh produce, the details needed to ensure the adequate safety of these commodities are elaborate and as diverse as the risks themselves. Education is essential to carry out the implementation of a food safety plan. The PSA Produce Safety Course is available in English and Spanish through a variety of entities, including Environ Health Associates Inc. of Florida. Produce growers, harvesters and packers are encouraged to complete the PSA course or schedule an in-house training session.

For a complimentary copy of the risk assessment document for tree fruit, contact Katherine Jones, administration manager at Environ Health Associates by calling 386-316-7266 or sending email to ROYCOSTAenvironhealth.kjm@gmail.com.

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