Contamination Alone May Not Be to Blame for 2018 Spike in US Cyclosporiasis Cases


Following a significant spike in cases of cyclosporiasis, the CDC is investigating whether changes in diagnostic testing may be partially responsible for the rise in recent case counts.

A new report from the Centers for Disease Control and Prevention (CDC) details a recent spike in cases of Cyclospora cases in the United States, which have increased by more than 10 times from 2016 to 2018.

Cyclospora cayetanensis is a microscopic protozoan parasite which causes cyclosporiasis, an intestinal illness. The parasite is transmitted to humans who ingest food and water contaminated with feces, with symptoms of infection typically appearing about 1 week following exposure. Cyclosporiasis symptoms may include watery diarrhea, frequent and sometimes explosive bowel movements, loss of appetite, weight loss, stomach cramping, bloating, increased gas, nausea, fatigue, vomiting, headache, and fever. These symptoms may persist for a few days to a month or longer. Cyclospora infections are also known as traveler’s diarrhea, as the parasite is endemic to certain tropical and subtropical countries frequented by tourists. In the United States, cyclosporiasis outbreaks are typically food-borne and caused by imported fresh produce such as basil, cilantro, and raspberries.

During the summer of 2018, health officials linked multistate outbreaks of cyclosporiasis to contaminated Del Monte pre-packaged vegetable trays as well as salads served at McDonald’s restaurants. Now, in a new report published on October 5, 2018, in the CDC’s Morbidity and Mortality Weekly Report, investigators say the recent outbreaks are noteworthy due to the multiple outbreaks and a large number of cases reported as a result. Following the 174 confirmed cases of cyclosporiasis that occurred in the United States in 2016 and the 623 cases reported in 2017, as of October 1, 2018, there have been 2,299 laboratory-confirmed cases for the year in 33 states.

The outbreak associated with the vegetable trays was identified in June and led to 250 laboratory-confirmed cyclosporiasis cases in 3 states while the outbreak associated with McDonald’s salads was identified in July and led to 511 cases in 11 states. In addition, the CDC and the US Food and Drug Administration (FDA) identified smaller clusters of cyclosporiasis cases associated with fresh basil and cilantro. Among the cases reported from May 1 to August 30, none of the infected individuals had traveled internationally within the 14 days prior to the onset of illness. While 160 patients were hospitalized, none died as a result of cyclosporiasis infection.

While the number of cases in the recent outbreaks was markedly higher than in prior years, authors of the report say they are investigating the cause of the sharp rise in cyclosporiasis. “This increase might be due, in part, to changes in diagnostic testing practices, including increased use of gastrointestinal molecular testing panels,” they explain in the report. “CDC is working with state public health partners to determine whether and to what extent changes in testing practices might have contributed to increased case detection and reporting.”

The CDC recommends washing fresh fruit and vegetables with clean running water in order to reduce the risk of food-borne illness and other contaminants; however, washing, even with the use of routine chemical disinfection or sanitization methods, is not likely to kill C cayetanensis. If patients present with a diarrheal illness that has lasted for over 3 days, health care providers should consider cyclosporiasis and ask their patients about recent food that they consumed prior to illness.

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