Surveillance for Laboratory-Confirmed Sporadic Cases of Cyclosporiasis --- United States, 1997--2008

Surveillance for Laboratory-Confirmed Sporadic Cases of Cyclosporiasis --- United States, 1997--2008
Surveillance Summaries
April 8, 2011 / 60(SS02);1-11




Rebecca L. Hall, MPH1,2

Jeffrey L. Jones, MD2

Barbara L. Herwaldt, MD2

1Atlanta Research and Education Foundation, Decatur, GA

2Division of Parasitic Diseases and Malaria, Center for Global Health, CDC


Corresponding author: Rebecca L. Hall, MPH, Center for Global Health, CDC, 4770 Buford Highway N.E., MS F-22, Atlanta, GA 30341. Telephone: 770-488-7319, Fax: 770-488-7761, E-mail: bqu5@cdc.gov.

Abstract
Problem/Condition: Cyclosporiasis is an enteric disease caused by the parasite Cyclospora cayetanensis. Cyclosporiasis is reported most commonly in tropical and subtropical regions. In the United States, outbreaks of cyclosporiasis associated with various types of imported fresh produce have been documented and described since the mid-1990s. No molecular tools are available for linking C. cayetanensis cases. National data regarding laboratory-confirmed sporadic cases (i.e., cases not linked to documented outbreaks) have not been summarized previously.

Reporting Period: This summary includes laboratory-confirmed sporadic cases that occurred during 1997--2008 and were reported to CDC by 2009.

Description of System: In January 1999, cyclosporiasis became a nationally notifiable disease, and, as of 2008, it was a reportable condition in 37 states, New York City (NYC), and the District of Columbia. For 1997--2008, CDC was notified of laboratory-confirmed cases via two active surveillance systems (the Cyclospora Sentinel Surveillance Network and the Foodborne Diseases Active Surveillance Network), two passive systems (the National Notifiable Diseases Surveillance System and the Public Health Laboratory Information System), and informal mechanisms (e.g., electronic mail).

Results: CDC was notified of 1,110 laboratory-confirmed sporadic cases of cyclosporiasis that occurred during 1997--2008. The overall population-adjusted incidence rates ranged from a low of 0.01 cases per 100,000 persons in 1997 to a high of 0.07 in 2002. Of the 1,110 cases, 849 (76.5%) were reported by seven states: 498 (44.9%) occurred in residents of Florida (228 cases), NYC (200 cases), and elsewhere in New York state (70 cases); and >50 cases were reported by each of five other states (Connecticut, Georgia, Massachusetts, New Jersey, and Pennsylvania). Overall, the case-patients' median age was 44 years (range: 3 months--96 years); 50.5% were female, 47.2% were male, and the sex was unknown for 2.3%. A total of 372 case-patients (33.5%) had a documented history of international travel during the 2-week period before symptom onset or diagnosis, 398 (35.9%) reported no international travel, and 340 (30.6%) had an unknown travel history. Some details about the travel were available for 317 (85.2%) of the case-patients with a known history of international travel; 142 (44.8%) had traveled to Mexico (60 persons), Guatemala (44 persons), or Peru (38 persons). Among the 398 case-patients classified as having domestically acquired cases, 124 persons (31.2%) lived in Florida, and 64 persons (16.1%) lived either in NYC (49 persons) or elsewhere in New York state (15 persons). The majority (278 [69.8%]) of onset or diagnosis dates for domestically acquired cases occurred during April--August.

Interpretation: Approximately one third of cases occurred in persons with a known history of international travel who might have become infected while traveling outside the continental United States. Domestically acquired cases were concentrated in time (spring and summer) and place (eastern and southeastern states): some of these cases probably were outbreak associated but were not linked to other cases, in part because of a lack of molecular tools.

Public Health Action: Surveillance for cases of cyclosporiasis and research to develop molecular methods for linking seemingly sporadic cases should remain U.S. public health priorities, in part to facilitate identification and investigation of outbreaks and to increase understanding of the biology of Cyclospora and the epidemiology of cyclosporiasis. Unidentified, uninvestigated cases and outbreaks represent missed opportunities to identify vehicles of infection, modes of contamination, and preventive measures. Travelers to known areas of endemicity should be advised that food and water precautions for Cyclospora are similar to those for other enteric pathogens, except that this parasite is unlikely to be killed by routine chemical disinfection or sanitizing methods. The diagnosis of cyclosporiasis should be considered for persons with persistent or remitting-relapsing diarrheal illness, and testing for Cyclospora should be requested explicitly.



Introduction

Cyclosporiasis is an enteric disease caused by the parasite Cyclospora cayetanensis, a unicellular, coccidian parasite transmitted by ingestion of infective oocysts (e.g., through contaminated food or water). The most common symptom is watery diarrhea. Although humans are the only known hosts of this Cyclospora species, direct person-to-person transmission is unlikely; the oocysts shed in feces require days to weeks under favorable environmental conditions to become infective (1,2). The need for Cyclospora oocysts to survive long enough both to sporulate and subsequently to be ingested by a susceptible person suggests that the oocysts are quite hardy (1,2) and unlikely to be killed by routine chemical disinfection or sanitizing methods used for food or water (3). The incubation period averages 1 week (range: ~2--14 days). Infection responds to treatment with trimethoprim-sulfamethoxazole, but untreated persons can have prolonged illness, with remitting-relapsing symptoms, for several weeks or months (1).

Cyclosporiasis is reported most commonly in tropical and subtropical regions. In retrospect, the first cases of cyclosporiasis documented in the literature occurred in 1977 and 1978 in Papua New Guinea (4). In the mid-1980s, several cases were described in U.S. travelers returning from Haiti and Mexico (5). In the mid-1990s, Cyclospora emerged as a foodborne pathogen of U.S. public health concern in the context of large, multistate outbreaks in 1996 and 1997, with >1,000 outbreak-associated cases reported in both years (1,2,6,7).

In June 1998, the Council of State and Territorial Epidemiologists (CSTE) voted to add cyclosporiasis to the list of nationally notifiable conditions (NNCs), effective January 1999 (8). As of 2008, cyclosporiasis was an explicitly reportable disease (i.e., it was listed as a specific disease or as a category of diseases on reportable disease lists) in 37 states, New York City (NYC), and the District of Columbia (DC) (9,10).

CDC, in collaboration with jurisdiction public health authorities, analyzes each reported case for epidemiologic evidence of linkage to other cases to facilitate rapid identification and investigation of outbreaks. U.S. clusters of cases have been documented almost every year since 1995. Various types of imported fresh produce (e.g., raspberries and snow peas from Guatemala and mesclun lettuce and basil from Peru) have been implicated (1,2,6,7,11,12). To date, U.S. publications about the epidemiology of cyclosporiasis have focused on outbreaks (1,2,6,7,11--16). This is the first summary of national data regarding laboratory-confirmed cases of cyclosporiasis that were not linked to documented outbreaks.

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Surveillance for Laboratory-Confirmed Sporadic Cases of Cyclosporiasis --- United States, 1997--2008