Cysticercosis Acquired in the United States | CDC EID

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Volume 17, Number 1–January 2011
Synopsis
Public Health Implications of Cysticercosis Acquired in the United States

Frank Sorvillo, Comments to Author Patricia Wilkins, Shira Shafir, and Mark Eberhard
Author affiliations: University of California, Los Angeles, California, USA (F. Sorvillo, S. Shafir); Touro University International, Cypress, California, USA (F. Sorvillo); Los Angeles County Department of Public Health, Los Angeles (F. Sorvillo); and Centers for Disease Control and Prevention, Atlanta, Georgia, USA (P. Wilkins, M. Eberhard)

Suggested citation for this article

Abstract
Cysticercosis has emerged as a cause of severe neurologic disease in the United States that primarily affects immigrants from Latin America. Moreover, the relevance of cysticercosis as a public health problem has been highlighted by local transmission. We searched the biomedical literature for reports documenting cases of cysticercosis acquired in the United States. A total of 78 cases, principally neurocysticercosis, were reported from 12 states during 1954–2005. A confirmed or presumptive source of infection was identified among household members or close personal contacts of 16 (21%) case-patients. Several factors, including the severe, potentially fatal, nature of cysticercosis; its fecal–oral route of transmission; the considerable economic effect; the availability of a sensitive and specific serologic test for infection by adult Taenia solium tapeworms; and the demonstrated ability to find a probable source of infection among contacts, all provide a compelling rationale for implementation of public health control efforts.

Cysticercosis, infection with the larval stage of the pork tapeworm, Taenia solium, is a known cause of illness and death in humans (1,2). Neurocysticercosis, the most serious form of the disease, occurs when larvae invade the central nervous system. The disease is dependent on a 2-host life cycle in which humans serve as the definitive host and pigs as the intermediate host. Eggs, which are directly infectious, are shed in the feces of humans infected with the adult tapeworm. When these eggs are ingested by pigs, larvae emerge from the eggs, penetrate the intestinal mucosa, and disseminate through the bloodstream to various tissues where the larval stage, or cysticercus, develops. The cycle is completed when humans, the only naturally infected definitive host, consume raw or undercooked pork containing cysticerci, which attach to the small intestine and develop into the adult tapeworm. However, humans may also become infected with the larval stage when they ingest T. solium tapeworm eggs, typically in contaminated food or water. Cysticercosis is therefore a fecal–oral-transmitted disease acquired by ingestion of eggs excreted in the feces of a human tapeworm carrier.

Cysticercosis is widely prevalent in Latin America, Asia, and parts of Africa; ≈50 million persons are infected globally (2,3). The disease is routinely seen in the United States in immigrants from disease-endemic regions, particularly Latin America (4,5). Recent attention has focused on cysticercosis as one of the neglected infections associated with poverty in the United States and also as a major cause of preventable epilepsy (6). The relevance of this parasitic infection as a public health problem in the United States has been highlighted by reports of autochthonous cases (7). This phenomenon was underscored by Schantz et al. in their report of an outbreak of cysticercosis in an Orthodox Jewish community in New York City in 1990–1991 (8). Several other publications, particularly over the past 25 years, have documented cysticercosis acquired in the United States (5,7–25). We present an aggregation of these published reports and discuss the attendant public health issues, including policy implications and approaches to prevention.

A search of PubMed was conducted by using the terms cysticercosis, neurocysticercosis, Taenia solium, taeniasis, and United States. Web-based searches were also conducted by using the same terms. Articles were reviewed for cases of locally acquired cysticercosis or reference to other publications documenting cysticercosis in persons without a history of travel outside the United States. Chapters in books dealing exclusively with cysticercosis and selected infectious disease texts were also reviewed.

We defined a case of cysticercosis as confirmed if there were clinical manifestations consistent with cysticercosis and a positive serologic test result or evidence of infection based on biopsy findings. A presumptive case was defined by clinical and imaging studies indicative of cysticercosis but lacking serologic or biopsy confirmation. An autochthonous case was defined as cysticercosis in a US-born person with no history of travel to a disease-endemic area before onset of symptoms indicated in the publication. Case-patients with any such travel history, independent of duration, or those for which information on travel was not reported, were excluded from consideration as locally acquired.

Twenty publications from 1954 through 2004 that documented 78 total cases of US-acquired cysticercosis from 12 states were identified (Table 1). Five (25%) reports detailing 44 (56.4%) cases were from California, all from Los Angeles County. Neurocysticercosis was most commonly reported (97.4%), although ocular (1) and subcutaneous (1) infections were also observed. No deaths were reported but long-term follow-up of clinical status was rarely reported. Demographic information was typically not provided. However, among studies reporting such data, the mean age of case-patients with locally acquired infection was 21.3 years (range 14 months–80 years). Ages for several pediatric patients were not reported; therefore, the available data on age must be viewed with caution. Among those few reports providing information on gender, 10 cases were in female patients and 6 were in male patients. Information on race or ethnicity was rarely included.

Nine reports documented multiple cases of US-acquired cysticercosis (5,7,9–11,15,17,19,23). In the New York City cluster of neurocysticercosis, 4 initial cases in which patients experienced seizures were identified, and an additional 7 persons were found to be seropositive. Investigation determined that the probable sources of infection were domestic workers with tapeworm infection who had emigrated from areas endemic for taeniasis/cysticercosis.

In a pilot cysticercosis surveillance system conducted in Los Angeles County from 1988 through 1990, ten locally acquired cases were identified and represented 7% of 138 total incident cases (15). The mean age of these patients was 13.7 years (range 4–33 years), and 7 (70%) patients were female. Most patients (70%) were Hispanic, 2 (20%) were white, and 1 (10%) was black. It is noteworthy that 7 additional cases of cysticercosis were identified in immigrants from disease-endemic areas who were long-term residents (mean length of residency 15.4 years) and had no history of additional travel or exposure outside the United States since their immigration (Table 2). This phenomenon has also been recognized by McCormick (20), who reported 20 cases of cysticercosis among foreign-born persons with >10 years residence in the United States and no history of subsequent travel, and by Earnest et al. (19), who documented 5 such cases with >7 years residence (Table 2). Given that the median incubation period for cysticercosis has been estimated to be 3.5 years (26), some of these cases may reflect additional local transmission and thus may indicate a risk for exposure to visitors (family and/or friends) from areas endemic for T. solium tapeworm infection or exposure at a social event where visitors or recent immigrants may have helped prepare food. Similarly, 32 cases of cysticercosis in US-born residents who had traveled to disease-endemic areas were noted in the articles reviewed. Given our strict definition, these were considered as travel-related cases but may in fact include cases of authochthonous cysticercosis.

Among this series of US-acquired cysticercosis a probable source (T. solium tapeworm carrier) was identified for 6 cases and presumptive source (close contacts from disease-endemic areas) for 10. This finding represents 21% of the cases despite the fact that information on a source of infection was not reported, and perhaps not sought, for most cases. In the Los Angeles County pilot surveillance system, follow-up, which included examination of stool samples from close contacts, was conducted for 72 patients. A tapeworm carrier(s) was found among contacts for 5 (7%) of these patients. Although the numbers were small, a probable source was identified more commonly among US-born patients (22%) than among those who were foreign born (5%).

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Cysticercosis Acquired in the United States | CDC EID

Suggested Citation for this Article

Sorvillo F, Wilkins P, Shafir S, Eberhard M. Public health implications of cysticercosis acquired in the United States. Emerg Infect Dis [serial on the Internet]. 2011 Jan [date cited]. http://www.cdc.gov/EID/content/17/1/1.htm

DOI: 10.3201/eid1701.101210

Comments to the Authors

Please use the form below to submit correspondence to the authors or contact them at the following address:

Frank Sorvillo, Department of Epidemiology, School of Public Health, University of California–Los Angeles, Box 951772, Los Angeles, CA 90095, USA; email: fsorvill@ucla.edu