Parasite Cyclospora is Latest Culprit in Foodborne Illness Outbreak

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August 30, 2013

Public health officials have been closely tracking a recent outbreak of cyclosporiasis, a type of intestinal infection caused by a single-celled parasite rare to the U.S. known as Cyclospora cayetanensis that has sickened more than 600 people and caused 45 hospitalizations as of August 28.

The Centers for Disease Control and Prevention (CDC) first became aware of the outbreak on June 28 when two cases of cyclosporiasis in Iowa were detected by the State Hygienic Laboratory, Iowa's state public health laboratory. Since then, Cyclospora infection has been reported in 22 states, including Arkansas, California, Connecticut, Florida, Georgia, Illinois, Iowa, Kansas, Louisiana, Minnesota, Missouri, Nebraska, New Jersey, New Hampshire, New York (including New York City), Ohio, South Dakota, Tennessee, Texas, Virginia, Wisconsin, and Wyoming. See the latest case count and the states affected at the CDC Cyclospora Outbreak web page.

Although the CDC has not established whether all of the cases are part of the same outbreak, an investigation by the Food and Drug Administration (FDA) revealed that illnesses in Nebraska and Iowa have been linked to bags of salad mix produced by Taylor Farms de Mexico. Teams of public health officials have since been dedicated to investigating the cause of infection in other states.

Typically, people contract cyclosporiasis by consuming food or water that is contaminated with the parasite. Because Cyclospora must be passed in a bowel movement and allowed time to incubate before becoming infectious, person-to-person transmission rarely, if ever, occurs. Symptoms usually develop about one week after ingesting the parasite. Some people, however, do not experience any symptoms. For those that do, symptoms may include watery diarrhea, loss of appetite, nausea, cramping, bloating, gas, fatigue, fever or other flu-like symptoms. These can last, in some cases, over two weeks. Though most people who are otherwise healthy will recover without treatment, a combination of antibiotics is typically prescribed. The infection is usually not deadly, but if not treated, symptoms can persist several weeks to months and may even return after a period of subsiding.

Testing for cyclosporiasis is important because it allows health officials to track the origins and spread of an outbreak as well as develop measures to prevent further cases. Symptoms can be mimicked by other gastrointestinal infections and testing helps definitively diagnose a Cyclospora infection. Testing involves collecting a stool sample and placing a portion of it on a slide, which is then treated with a special stain and examined under a microscope by a trained laboratorian.

Since Cyclospora infections are uncommon in the U.S., most U.S. laboratories do not routinely screen for it and the test must be specifically requested by health practitioners. As an example, officials from the Iowa Department of Public Health credited news media attention and digital communications as instrumental in alerting patients and health care providers to increase testing for the uncommon infection. Physicians are encouraged to request testing for Cyclospora whenever symptoms are prolonged. The CDC is using computer-assisted technology (telepathology or telediagnosis) that allows state and local health departments to submit digital photos of stained slides to CDC's parasitology experts for review and confirmation of the diagnosis of cyclosporiasis.

As with other foodborne illnesses, the FDA recommends that consumers use safe food handling practices, including washing hands, cooking surfaces, and utensils, as well as thoroughly washing fresh produce prior to eating to reduce the spread of Cyclospora infection. The CDC cautions that the parasite is particularly resilient and is not easily killed by routine disinfecting methods. The best prevention is to avoid food and water sources that are known to be contaminated with stool. Treatment of water with chlorine or iodine is not effective in killing Cyclospora.

In the Nebraska and Iowa cyclosporiasis cases, contaminated salad mixes were distributed to restaurants and grocery stores in the two states, and the FDA reported that four restaurants—including two large chains—received the tainted supply. As of yet, no reported illnesses have been traced to bags purchased by consumers. Taylor Farms has cooperated with FDA officials, agreeing to stop all shipments of prepackaged salad mix to the U.S. (in addition to other fresh produce items) until further notice.

The first documented cases of Cyclospora infection were detected in Papua New Guinea in 1977. Since the mid-1990s, cyclosporiasis outbreaks have been tied to imported fresh produce, such as the Guatemalan raspberries and snow peas and Peruvian mesclun lettuce and basil implicated in previous years. Cyclosporiasis is endemic to tropic and subtropic regions, and many of those in the U.S. who develop the infection when it is unrelated to an outbreak have traveled to, and subsequently contracted it from, those areas.

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

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Hall, Rebecca L. et. al. (April 8, 2011). Surveillance for Laboratory-Confirmed Sporadic Cases of Cyclosporiasis - United States, 1997—2008. Centers for Disease Control and Prevention: Morbidity and Mortality Weekly Report. Available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/ss6002a1.htm through http://www.cdc.gov/mmwr. Accessed August 2013.

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Jaslow, Ryan (Aug. 2, 2013). Salads served at Olive Garden, Red Lobster tied to cyclospora outbreak in 2 states, FDA says. CBS News online. Available online at http://www.cbsnews.com/8301-204_162-57596833/salads-served-at-olive-garden-red-lobster-tied-to-cyclospora-outbreak-in-2-states-fda-says through http://www.cbsnews.com. Accessed August 2013.

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