Correspondence
Cyclosporiasis and Raspberries
N Engl J Med 1997; 337:1170-1172October 16, 1997
- Article
To the Editor:
The meticulous epidemiologic investigation reported by Herwaldt et al. (May 29 issue) 1 establishes the association between a large outbreak of cyclosporiasis in North America and the consumption of raspberries imported from Guatemala. The study, however, provides no evidence of current or previous cyclospora contamination or infections on the farms where the implicated raspberries were grown, picked, and packed. The only reported microbiologic finding on the suspected source is “intermittent bacterial contamination, including fecal coliforms or Escherichia coli,” of agricultural-water samples from the implicated farms as the outbreak subsided. Strictly speaking, therefore, where, when, and how the Guatemalan raspberries became contaminated remain unclear. Could the contamination have occurred during transport or storage rather than on the farms? Could the empty packages (plastic “clamshells”) have been contaminated with cyclospora oocysts before reaching the farms?
1 ReferencesBruno Simini, M.D.
Ospedale Generale Provinciale, 55100 Lucca, Italy1
Herwaldt BL, Ackers M-L, Cyclospora Working Group
Full Text | Web of Science | Medline
To the Editor:
In his editorial on the outbreak of cyclosporiasis,1 Dr. Osterholm proposes the use of ionizing radiation to reduce the bacterial and parasitic causes of foodborne disease. Of the large number of radiolytic products formed during this process, some are unequivocal mutagens and carcinogens — for example, formaldehyde.2 Furthermore, the pathogens are not eliminated but only reduced in number by the permitted doses of radiation, in order to preserve the organoleptic properties of the food. The radiation-resistant surviving organisms and their progeny will populate the gastrointestinal tract in persons consuming the food. This point has been ignored by the agencies that have recommended irradiation to reduce contamination of food. . . .
2 ReferencesGeorge L. Tritsch, Ph.D.
State University of New York at Buffalo, Buffalo, NY 14263Douglas E. Tritsch, M.S.
University of Dayton Research Institute, Dayton, OH 45469-01201
Osterholm MT . Cyclosporiasis and raspberries -- lessons for the future. N Engl J Med 1997;336:1597-1599
Full Text | Web of Science | Medline2
Steward FC ,Holsten RD ,Sugii M . Direct and indirect effects of radiation: the radiolysis of sugar. Nature 1967;213:178-178
CrossRef | Web of Science | Medline
To the Editor:
Irradiation of food appears to be safe and does not compromise the quality of food products. But the cost of building food-irradiation facilities is enormous. Repairs of nuclear facilities are costly, and accidents, although unlikely, can have devastating effects on public health. Moreover, the life span of such facilities is limited, the cost of dismantling them is enormous, and the problem of disposing of spent fuel is insurmountable.
Marc H. Lavietes, M.D.
University of Medicine and Dentistry of New Jersey, Newark, NJ 07103-2406To the Editor:
Dr. Osterholm is to be congratulated for advocating the use of ionizing energy (irradiation) for food pasteurization. As he notes in his editorial, there have been substantial changes in the food Americans eat and where they get it. The outbreak of cyclosporiasis that was related to the consumption of raspberries1 and a recent outbreak of hepatitis A related to the consumption of strawberries 2 are examples of foodborne infectious diseases involving imported produce. But domestic produce is also not safe, as exemplified by the numerous recent outbreaks of E. coli O157:H7 infection related to the consumption of such diverse foods as apple juice and ground beef.3
As Dr. Osterholm indicates, the use of ionizing radiation for cold pasteurization of produce is safe, practical, and highly effective in reducing the number of microorganisms in food.4 Like microwaves, another form of irradiation that most of us use on a daily basis for food preparation, this method is nonradioactive.
Even though regulations to protect foods from contamination may be in place both in the United States and abroad, there is no assurance that they are enforced or, for that matter, effective. The enormous costs of foodborne outbreaks (an estimated $8 billion to $23 billion annually in lost productivity, medical costs, and related expenses4) could be avoided if foodstuffs were decontaminated with the use of ionizing radiation. Several U.S. regulatory agencies, including the Food and Drug Administration (FDA), have endorsed this highly effective, safe method of cold pasteurization.5 Food processors and distributors should be required to use it.
5 ReferencesFranklin R. Cockerill, III, M.D.
Mayo Clinic, Rochester, MN 559051
Herwaldt BL, Ackers M-L, Cyclospora Working Group
Full Text | Web of Science | Medline2
Hepatitis A associated with consumption of frozen strawberries -- Michigan, March 1997MMWR Morb Mortal Wkly Rep 1997;46:288, 295-288, 295
3
Armstrong GL ,Hollingsworth J ,Morris JG Jr . Emerging foodborne pathogens: Escherichia coli O157:H7 as a model of entry of a new pathogen into the food supply of the developed world. Epidemiol Rev 1996;18:29-51
Web of Science | Medline4
Loaharanu P . Irradiation as a cold pasteurization process of food. Vet Parasitol 1996;64:71-82
CrossRef | Web of Science | Medline5
Monk JD ,Beuchat LR ,Doyle MP . Irradiation inactivation of food-borne microorganisms. J Food Prot 1995;58:197-208
Web of Science
Author/Editor Response
The authors reply:
To the Editor: Unfortunately, we cannot yet answer the related questions of where and how the raspberries, which were implicated in the outbreak on the basis of epidemiologic data, became contaminated. We faced two constraints. First, the laboratory techniques currently available for testing produce and other environmental samples for cyclospora oocysts are relatively insensitive and nonstandardized. Second, our investigation in Guatemala was conducted after the period of the outbreak. However, we were able to observe the ways in which raspberries are grown, picked, sorted, packed, cooled, transported, and inspected. No single packing or storage facility in Guatemala, exporter, type of shipping container, shipment, airline carrier, U.S. port of entry or cargo-clearance area, importer, distributor, retailer, or food handler was linked to all 29 events for which we had good data about the source of the implicated raspberries. We concluded that some practice or attribute common to multiple farms was the most likely explanation for the outbreak.
It is unlikely that the plastic clamshells in which the raspberries were packed were the source of the contamination, because most growers did not reuse the clamshells. If reused, they were first washed and air-dried. No data are available on the survival of cyclospora oocysts on clamshells or other surfaces. However, on the basis of limited data for Cryptosporidium parvum 1 and other coccidian parasites, cyclospora oocysts are unlikely to survive extended periods of air-drying at room temperature.
The question of how the raspberries became contaminated remains of concern because fresh raspberries imported from Guatemala were implicated 2 in another outbreak of cyclosporiasis in the United States and Canada in the spring of 1997; no outbreaks of cyclosporiasis have been noted in association with fall crops of Guatemalan raspberries. In addition, mesclun lettuce and basil (not from Guatemala) have been identified as the probable vehicles of infection for other outbreaks of cyclosporiasis that occurred in the United States in 1997 and are still being investigated.2,3 All these outbreaks underscore the need for an improved understanding of the epidemiology of cyclospora and for stronger prevention and control measures to ensure that produce eaten raw is kept free of microbial contamination all the way from farm to table.
We also wish to note that the name of Dr. Bradley A. Connor, of New York Hospital–Cornell University Medical College, was inadvertently omitted from the acknowledgments section of our article.
3 ReferencesBarbara L. Herwaldt, M.D., M.P.H.
Marta-Louise Ackers, M.D.
Centers for Disease Control and Prevention, Atlanta, GA 30341-3724for the Cyclospora Working Group
1
Robertson LJ ,Campbell AT ,Smith HV . Survival of Cryptosporidium parvum oocysts under various environmental pressures. Appl Environ Microbiol 1992;58:3494-3500
Web of Science | Medline2
Update: outbreaks of cyclosporiasis -- United States and Canada, 1997
Medline3
Outbreak of cyclosporiasis -- northern Virginia-Washington, DC.-Baltimore, Maryland, metropolitan area, 1997. MMWR Morb Mortal Wkly Rep 1997;46:689-691
Medline
Author/Editor Response
Most of my editorial was related to Cyclospora cayetanensis as an emerging infectious-disease agent, but not surprisingly, the responses are about my concluding paragraph on food irradiation. Unfortunately, this valuable public health tool remains a point of great controversy.
Tritsch and Tritsch illustrate the use of inadequate science to suggest that ionizing irradiation for food pasteurization is unsafe. First, any process that heats food, including cooking, exposure to light, microwaving, and irradiation, creates free radicals, or highly reactive molecules, in the food. However, multiple studies have documented that no radiolytic products have been found in irradiated foods that have not been found in much greater amounts in food exposed to ordinary cooking. Anti-irradiation activists frequently state that irradiation creates unique radiolytic products that can be toxic, carcinogenic, or mutagenic. No such products have been found in irradiated foods, despite the ability to detect the substances down to the part-per-quadrillion level.1 Repeated irradiation does not create microorganisms that are more resistant to irradiation or able to produce more toxins than preceding generations. Evidence from numerous experiments shows that such mutations can occur only under laboratory conditions and that the mutated microorganisms cannot survive in competition with unirradiated and concurrent microorganisms.2
Lavietes suggests that building irradiation facilities is too costly and unsafe. More than 40 irradiation facilities in the United States currently sterilize medical devices and supplies in a cost-effective and safe manner. Some of the very equipment that Lavietes uses in his own practice probably has been irradiated for reasons of safety. In most instances, the design of food irradiators will be very similar to medical-sterilization irradiators because of the similar requirements for licensing the facilities. The use of irradiation facilities for processing food may prove to be cost effective and safe, as shown with the use of such facilities for medical devices and supplies. Irradiated foods have been sold on a limited basis in this country and have competed very favorably with nonirradiated foods.
I appreciate Cockerill's reinforcement of the scientific facts surrounding the use of food irradiation. Both the FDA and the Department of Agriculture regulate the irradiation of various food products. It is the job of the public health and medical communities to educate consumers, which in turn will convince the food wholesalers and retailers that the widespread use of irradiation or other cold-pasteurization processes is in the best interest of all of us.
2 ReferencesMichael T. Osterholm, Ph.D., M.P.H.
Minnesota Department of Health, Minneapolis, MN 55440
