MEDSCAPE CME ACTIVITY
Taenia solium Tapeworm Infection, Oregon, 2006–2009
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Release date: May 25, 2011; Expiration date: May 25, 2012
Learning Objectives
Upon completion of this activity, participants will be able to:
•Describe the epidemiology of cysticercosis in Oregon as based on a surveillance study
•Describe morbidity and mortality associated with cysticercosis as based on that surveillance study
•Describe goals of public health interventions for cysticercosis in Oregon as based on that study
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Authors
Disclosures: Seth O’Neal, MD; John Noh; Patricia Wilkins, PhD; William Keene, PhD, MPH; William Lambert, PhD; James Anderson, MD; Jenifer Compton Luman, MD; and John Townes, MD, have disclosed no relevant financial relationships.
T. solium Tapeworm Infection, Oregon, CME Activity | CDC EID
EID Journal Home > Volume 17, Number 6–June 2011
Research
Taenia solium Tapeworm Infection, Oregon, 2006–2009
Seth O'Neal, John Noh, Patricia Wilkins, William Keene, William Lambert, James Anderson, Jenifer Compton Luman, and John Townes
Author affiliations: Oregon Health & Science University, Portland, Oregon, USA (S. O'Neal, W. Lambert, J. Anderson, J. Compton Luman, J. Townes); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (J. Noh, P. Wilkins); and Oregon Department of Human Services, Portland (W. Keene)
Suggested citation for this article
Abstract
Neurocysticercosis (NCC) is a parasitic infection of the central nervous system caused by Taenia solium larval cysts. Its epidemiology in cysticercosis-nonendemic regions is poorly understood, and the role of public health institutions is unclear. To determine the incidence of NCC and to pilot screening of household contacts for tapeworms, we conducted population-based active surveillance in Oregon. We screened for T. solium infection by examining hospital billing codes and medical charts for NCC diagnosed during January 1, 2006–December 31, 2009 and collecting fecal and blood samples from household contacts of recent case-patients. We identified 87 case-patients, for an annual incidence of 0.5 cases per 100,000 general population and 5.8 cases per 100,000 Hispanics. In 22 households, we confirmed 2 additional NCC case-patients but no current adult intestinal tapeworm infections. NCC is of clinical and public health concern in Oregon, particularly among Hispanics. Public health intervention should focus on family members because household investigations can identify additional case-patients.
Neurocysticercosis (NCC) is a parasitic disease caused by central nervous system infection with Taenia solium larval cysts. It is the most common helminthic infection of the central nervous system and a leading cause of acquired epilepsy in Latin America, Southeast Asia, and central Africa (1,2). The disease also is increasingly of clinical and public health concern in the United States, primarily in immigrants and travelers from cysticercosis-endemic regions (3–5).
Cysticercosis is acquired through fecal–oral transmission of tapeworm eggs shed in the feces of a human carrying intestinal tapeworms. Ingested eggs release oncospheres, which invade the intestinal mucosa and disseminate throughout the body to form larval cysts. NCC occurs when cysts develop in the central nervous system and is the primary source of illness and death (6). The tapeworm's complete life cycle occurs in regions with poor sanitary infrastructure, where foraging pigs have access to human feces. Most NCC cases in the United States probably were acquired in cysticercosis-endemic areas by immigrants or travelers who entered the United States already infected with cysts (3). However, immigrants and travelers also can harbor intestinal tapeworms, and domestic transmission of NCC does occur (7,8).
Few states require reporting of cysticercosis; thus, population-based epidemiologic data in the United States are limited. Even in jurisdictions that require reporting, the clinical nature of NCC diagnosis complicates surveillance efforts because no single laboratory test definitively establishes the diagnosis. Surveillance therefore relies on clinician or institutional reporting. In 1989, California became the first state to require reporting; 112 cysticercosis cases were reported during the first year, for a crude annual incidence of 1.5 cases per 100,000 Hispanics (9). A retrospective case-series from Oregon based on hospital discharge diagnoses during 1995–2000 estimated an annual incidence of 0.2 cases per 100,000 general population and 3.1 cases per 100,000 Hispanics (10). In 5 cases, no exposure to a cysticercosis-endemic area was documented, which suggests the possibility of local transmission.
Oregon adopted administrative rules for T. solium reporting in 2002 after the coroner's examination implicated hydrocephalus secondary to obstructing ventricular cysts in 2 unexplained deaths (10). However, no subsequent efforts were undertaken to stimulate passive reporting or to actively find unreported cases. As a result, only 7 NCC cases, all in Hispanics, were reported to public health officials during the first 5 years of reporting. Oregon has a rapidly growing Hispanic population, which currently represents 11% of the total population. Approximately half of all Oregon Hispanics report birth outside the United States (11). In the context of an increasing population at risk, the small number of passively reported cases suggests inadequate surveillance.
Identification and treatment of tapeworm carriers in the United States could prevent additional NCC cases. However, intestinal tapeworm infection produces few symptoms, and the prevalence is typically <1%–2%, even in regions where cysticercosis is endemic (12). During the 1980s, Los Angeles (LA) County, California, adopted a program of screening for tapeworm carriers with some success. By screening household members of NCC case-patients using light microscopy on fecal samples, the county identified an intestinal tapeworm carrier in 7% of its overall investigations and in 22% of investigations involving domestically acquired NCC (13). Improved screening methods have been developed in the interim, including an ELISA for Taenia sp. coproantigens in feces and an enzyme-linked immunoelectrotransfer blot (EITB) for serum antibodies against T. solium tapeworm (14,15). Serologic methods are desirable because they are specific to T. solium intestinal infection and highly sensitive (99%) and avoid the collection and processing of potentially infectious feces (15). Our objective was to evaluate the utility of public health surveillance for T. solium infection in Oregon. We implemented population-based active surveillance to determine the incidence of cysticercosis. We also piloted screening specifically for additional T. solium infection among affected households by using a combination of symptom screening, laboratory analysis of fecal and serum specimens, and radiographic imaging. full-text: T. solium Tapeworm Infection, Oregon | CDC EID
Suggested Citation for this Article
O'Neal S, Noh J, Wilkins P, Keene W, Lambert W, Anderson J, et al. Taenia solium tapeworm infection, Oregon, 2006–2009. Emerg Infect Dis [serial on the Internet]. 2011 Jun [date cited]. http://www.cdc.gov/EID/content/17/6/1030.htm
DOI: 10.3201/eid1706.101397
Comments to the Authors
Please use the form below to submit correspondence to the authors or contact them at the following address:
Seth O'Neal, 3181 SW Sam Jackson Park Rd, CSB 681, Portland, OR 97239, USA; email: oneals@ohsu.edu
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