Salmonella — the pathogen behind an ongoing foodborne illness outbreak that has sickened 173 people across 21 states, killing one — is a normal inhabitant of the intestinal tract of many birds, reptiles and mammals.
The possibility that an agricultural product such as papayas may be contaminated with Salmonella is impossible to eradicate; however, the risk of widespread contamination can be controlled through careful attention to current best sanitary practices in the cultivation, harvesting and packing of raw produce. Failure to do so can result in a vicious cycle of contamination in fields, packing houses and the distribution system.
Cultivation, harvesting and packing
The papaya is a fast-growing, tree-like herbaceous plant, which is at home in tropical and semi-tropical climates and is cultivated extensively across southeastern Mexico, according to a report issued by the University of Florida IFAS Extension Service. The most recent report from Mexico’s Secretaría de Agricultura, Ganadería, Desarrollo Rural, Pesca y Alimentación (Ministry of Agriculture, Livestock, Rural Development, Fisheries and Food) shows Mexico to be the fifth largest producer of papayas in the world.
The papaya plant is propagated from seeds, with seedlings transplanted into fields when they are of sufficient size. The plant matures in six to nine months in warmer regions. Susceptible to a variety of plant diseases and pests, such as root rot, powdery mildew, papaya ringspot virus, fruit fly and white fly, papaya plants usually have an abbreviated commercial lifespan of two to three years, according to information from the University of Hawaii. It is not unusual for a papaya plant to only produce a single crop in its lifetime.
Once harvested and delivered to the packing house, each papaya is graded according to ripeness and size. Next, the fruit is sorted according to size a second time, as well as shape, and color. It is also examined for insect or mechanical damage.
The sorted fruit is generally washed in large vats of chlorinated tap water to remove dirt, debris and insect contamination. Depending upon the condition of the fruit and the expected final destination, it may be subjected to additional treatments, including a hot water bath or a fungicide dip. After air-drying, the fruit is packed for shipment.
2011 Salmonella Agona outbreak
In 2011, the Centers for Disease Control and Prevention and the Food and Drug Administration investigated a Salmonella Agona outbreak that was traced to contaminated papayas imported from Mexico. The papayas were grown and packed by Agromod SA de CV of Chiapas, Mexico, and distributed by Agromod Produce Inc. of McAllen, Texas.
The Agromod papaya plantation had an interconnected drainage ditch system, according to information presented in 2013 during the annual educational conference of the National Environmental Health Association (NEHA).
The marsh-like environment of the drainage ditches was a haven for waterfowl, frogs and other wildlife, and provided perfect growth conditions for pathogenic bacteria. During heavy rain and flooding, the ditches overflowed into the soil surrounding the trees, impregnating the soil with pathogens from the water.
During an on-site inspection of Agromod’s plantation and packing house, investigators from FDA recovered a full two dozen different types of Salmonella, including the Salmonella Agona outbreak strain. Salmonella-positive samples were drawn from fields where the papaya grew and from packing-house drains.
The crops at Agromod were harvested by two-person teams. One person worked at tree level, picking fruit and handing or tossing it to the other person below. The second person laid each papaya onto a piece of poly foam on the unprotected soil. The foam was wrapped around the fruit, which was loaded into foam-lined bins for transport to the packing house.
It was common practice at Agromod for the sheets of poly foam to be reused for up to 15 days before being discarded, helping to spread contamination from the fields to the fruit, packing house and back again.
Once in the packing house, the fruit was washed in large vats of water. The level of chlorine in the wash water was not properly monitored or controlled, allowing Salmonella to spread throughout an entire batch of papayas.
The wash water was discharged into the drainage ditch system, returning Salmonella to the fields in a vicious cycle of contamination.
In response to the extent of Salmonella contamination brought to light during the investigation of the 2011 outbreak, FDA instituted Import Alert #21-17, “Countrywide Detention Without Physical Examination Of Papaya From Mexico.” Firms that provided documentation of five consecutive Salmonella-negative commercial shipments qualified for an exemption from the automatic detention at the U.S. border.
Concurrent with FDA’s initiation of the Import Alert, Mexico’s Servicio Nacional de Sanidad, Inocuidad y Calidad Agroalimentaria (National Service for Health, Safety and Agrifood Quality) (SENASICA ) unveiled a plan to assist that country’s papaya growers, packers and shippers in addressing the issues of safe growing and handling of the fruit.
Notwithstanding the efforts of multiple agencies in both countries, the United States is once again in the throes of an outbreak of Salmonella that is associated with consumption of fresh, whole papayas imported from Mexico.
As of Aug. 18 when the CDC posted it’s most recent outbreak update, 173 people had been confirmed sick across 21 states, with 58 hospitalizations, and one death on New York City. The CDC warns that the number of confirmed illnesses is likely to increase.
Thus far FDA has identified one farm in connection with the contaminated papaya. That farm, Carica de Campeche, has been supplying papayas to the U.S. market under an Import Alert exemption since 2015.
According to a spokesperson from FDA, at present there are no specific ongoing testing or inspection requirements that a producer must meet in order to maintain an exemption from automatic detention, although a firm is expected to “… continue to provide the commodity in a wholesome manner and follow all the regulatory requirements of FDA.”
The FDA revoked the exemption granted to Carica de Campeche under Import Alert 21-17 on Aug. 7.
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