Cyclosporiasis Spreads to 20 States
ABSTRACT & COMMENTARY
By Stan Deresinski, MD, FACP, FIDSA
Clinical Professor of Medicine, Stanford University, Hospital Epidemiologist, Sequoia Hospital, Redwood City, CA, Editor of Infectious Disease Alert.
SOURCE: Centers for Disease Control and Prevention: Investigation of an outbreak of cyclosporiasis in the United States: ow.ly/nX03j
SYNOPSIS: An outbreak of cyclosporiasis in the U.S. traced to lettuce has infected hundreds of individuals.
The notification of the CDC of 2 laboratory-confirmed cases of cyclospora infections on June 28, 2013 was their first evidence of an outbreak that, as of August 20, 2013, had reached 593 cases in 20 states with at least 36 hospitalizations. (See map below.) Most of the illness onset dates have ranged from mid-June through mid-July. (See chart, p. 139) Texas accounted for 247 cases. Investigations performed in Iowa and Nebraska indicated that the source was a commercial salad mix.
Cyclosporiasis is endemic in many countries in tropical and subtropical areas and many infections occur in travelers. Foodborne outbreaks in the U.S. have repeatedly been linked to imported produce, including raspberries, snow peas, and lettuce.1,2
Oocysts of this sporozoan parasite that are excreted in the feces are not themselves infective but require days or weeks for sporulation to the infective form that then may contaminate food or water. After they are ingested, the sporocysts, each containing 2 elongated sporozoites, exist within the gastrointestinal tract. The sporozoites then invade small intestine mucosal epithelial cells where they multiply and mature into oocysts. Cyclospora are resistant to disinfectants usually used in water and in food processing.
Cyclospora can be detected in stool specimens (preferably concentrated samples) by use of a modified acid fast stain. At least 3 specimens should be examined before accepting the testing as being negative. Alternatively, taking advantage of the fact that the oocysts naturally exhibit intense blue autofluorescence, the organism can be visualized by UV fluorescence microscopy. CDC can perform 18S rRNA amplification and sequencing on DNA extracted from stool for identification to the species level. To date, however, all human cases for whom speciation has been performed appear to have resulted from infection with Cyclospora cayatanensis.
In contrast to travelers and those infected in the U.S., infection of residents of endemic areas is often asymptomatic.2 Symptomatic infection results in loss of appetite, nausea, abdominal cramping and flatulence, low-grade fever, and diarrhea. Treatment is with trimethoprim-sulfamethoxazole; there is no known effective alternative.
- CDC. Surveillance for laboratory-confirmed sporadic cases of cyclosporiasis—United States, 1997-2008. MMWR 2011;60:1-11.
- Ortega YR, et al. Update on Cyclospora cayetanensis, a food-borne and waterborne parasite. Clin Microbiol Rev 2010; 23:218-34.