John Noh

Schistosomiasis in Lake Malawi

BACKGROUND In 1992 two US Peace Corps volunteers (PCVs) developed central nervous system schistosomiasis due to infection with Schistosoma haematobium following recreational water exposure at Cape Maclear on Lake Malawi, an African lake considered by many to be free of schistosomiasis. To determine the transmission potential and risk for aquiring schistosomiasis in Lake Malawi, a cross-sectional survey of resident expatriates and visitors to Malawi was done during March and April, 1993. METHODS A volunteer cohort of expatriates and visitors representing a cross-section of Malawis foregn population answered detailed questions about freshwater contact and provided blood specimens to determine the seroprevalence of S haematobium and S mansoni by ELISA and immunoblot analyses. A survey for vector snails was conducted along Lake Malawis southwestern shore. FINDINGS The study population of 955 included 305 US citizens and 650 non-US foreign nationals. 303 of the study population had serological evidence of current or past schistosome infection. Seroprevalence was 32% (141/440) among expatriates whose freshwater exposure was limited to Lake Malawi; S haematobium antibodies were found in 135 of 141 (96%) seropositive specimens. Risk of seropositivity increased with the number of freshwater exposures at Lake Malawi resorts. Although many resort areas in the southwestern lake region posed a significant risk, Cape Maclear was the location most strongly associated with seropositivity (OR 2.9, 95% Cl 1.6-5.1). Schistosome-infected Bulinus globosus, the snail vector of S haematobium in Malawi, were found at Cape Maclear and other locations along the lakeshore. INTERPRETATION S haematobium infection is highly prevalent among expatriates and tourists in Malawi. Recreational water contact at popular resorts on Lake Malawi is the most likely source of infection. Transmission of schistosomiasis is occurring in Lake Malawi, a previously under-recognised site of transmission.

Characterization of the 8-Kilodalton Antigens of Taenia solium Metacestodes and Evaluation of Their Use in an Enzyme-Linked Immunosorbent Assay for Serodiagnosis

ABSTRACT The Western blot for cysticercosis, which uses lentil lectin purified glycoprotein (LLGP) antigens extracted from the metacestode of Taenia solium, has been the “gold standard” serodiagnostic assay since it was first described in 1989. We report that the diagnostic antigens at 14, 18, and 21 kDa, as well as some larger disulfide-bonded antigens, are actually all members of a very closely related family of proteins, the 8-kDa antigens. The genes for 18 unique, mature proteins have been identified. Nine of these were chemically synthesized and tested in an enzyme-linked immunosorbent assay with a battery of defined serum samples, including 32 cysticercosis-positive serum samples reactive with the 8-kDa antigens of LLGP on Western blotting, 34 serum samples from patients with other parasitic infections, and 15 normal human serum samples. One of the 8-kDa antigens, TsRS1, is 100% sensitive and 100% specific. TsRS1 will be one component of a cocktail of three to four synthetic or recombinant antigens, based on the diagnostic bands of the Western blot, which will be used for the serodiagnosis of cysticercosis.

Neurocysticercosis in Persons with Epilepsy in Medellín, Colombia

Summary: Purpose: A prospective series of 643 persons with epilepsy attending a reference neurologic center in Medellin, Colombia, was examined by computed tomography (CT scan) or serology or both with the enzyme‐linked immunoelectrotransfer blot assay (EITB) to assess the prevalence of Taenia solium cysticercosis.

Development and evaluation of a magnetic immunochromatographic test to detect Taenia solium, which causes taeniasis and neurocysticercosis in humans.

ABSTRACT Taeniasis/cysticercosis caused by Taenia solium is a frequent parasitic infection of the human brain in most of the world. Rapid and simple screening tools to identify taeniasis and cysticercosis cases are needed for control programs, mostly to identify tapeworm carriers which are the source of infection and need to be treated, or as tools for point-of-care case detection or confirmation. These screening assays should be affordable, reliable, rapid, and easy to perform. Immunochromatographic tests meet these criteria. To demonstrate proof of principle, we developed and evaluated two magnetic immunochromatographic tests (MICTs) for detection of human Taenia solium taeniasis antibodies (ES33-MICT) and neurocysticercosis antibodies (T24-MICT). These assays detected stage-specific antibodies by using two recombinant proteins, rES33 for detection of taeniasis antibodies and rT24H for detection of cysticercosis antibodies. The sensitivity and specificity of the ES33-MICT to detect taeniasis infections were 94.5% and 96%, respectively, and those of the T24-MICT to detect cases of human cysticercosis with two or more viable brain cysts were 93.9% and 98.9%, respectively. These data provide proof of principle that the ES33- and T24-MICTs provide rapid and suitable methods to identify individuals with taeniasis and cysticercosis.

Multiantigen Print Immunoassay for Comparison of Diagnostic Antigens for Taenia solium Cysticercosis and Taeniasis

ABSTRACT One of the best-characterized tests for the diagnosis of neurocysticercosis is the enzyme-linked immunoelectrotransfer blot assay, developed at the CDC, which uses lentil lectin-purified glycoproteins (LLGPs) extracted from Taenia solium cysticerci. The purification of the LLGP antigens has been difficult to standardize, and the polyacrylamide gel system used for the immunoblot assay is not easily transferable to other laboratories. In this study, we developed a multiantigen printing immunoassay (MAPIA) to compare the performance of multiple recombinant Taenia solium proteins with the potential for the detection of cysticercosis and taeniasis. We prepared MAPIA strips using six cysticercosis and two taeniasis diagnostic proteins and compared the performance of the proteins with sera collected from defined cysticercosis and taeniasis cases. Of the six cysticercosis antigens, rT24H performed well in detecting cases with two or more viable cysts in the brain (sensitivity and specificity, 97% and 99.4%, respectively); the use of a combination of cysticercosis antigens did not improve the sensitivity of the test and decreased the specificity. None of the antigens could differentiate the different clinical presentations of cysticercosis. Both of the taeniasis antigens (rES33 and rES38) had the same sensitivity of 99.4% and specificities of 93.9% and 94.5%, respectively. Some cross-reactivity against rES33 and rES38 was found, especially with sera from cases infected with Schistosoma mansoni. We conclude that MAPIA is a simple and effective tool that may be used to compare antibody responses to different cysticercosis and taeniasis antigens and, in this case, may be useful for the rapid detection of T. solium cases.

Persistence of passively transferred antibodies in porcine Taenia solium cysticercosiss

Abstract We evaluated the presence and persistence of anticysticercal antibodies in piglets born to Taenia solium infected sows. Infected sows from a disease-endemic area of Peru were transported to a nondisease-endemic area and impregnated. Serum samples were collected from sows and piglets on Day 2 through Week 35 after birth. Using an immunoblot specific for cysticercosis, Ig isotypes to 7 cyst antigens were measured and quantified. Serum samples from the piglets contained detectable antibodies from Week 1 through Week 35 (27 weeks after weaning). The primary Ig isotype present in both sows and piglets was IgG. Antibodies did not appear in piglet serum samples until after suckling, demonstrating that anti-cysticercal antibodies are transferred solely via colostrum. Our data have shown that maternally transferred antibodies to cyst antigens may persist through much of a pig’s life. Therefore, the presence of passively transferred antibodies must be considered in studies that examine the prevalence of cysticercosis in pigs. Furthermore, when designing control strategies for cysticercosis, careful evaluation and selection of sentinel pigs becomes a crucial component of sentinel selection.

Exposure to Multiple Parasites Is Associated with the Prevalence of Active Convulsive Epilepsy in Sub-Saharan Africa

Background Epilepsy is common in developing countries, and it is often associated with parasitic infections. We investigated the relationship between exposure to parasitic infections, particularly multiple infections and active convulsive epilepsy (ACE), in five sites across sub-Saharan Africa. Methods and Findings A case-control design that matched on age and location was used. Blood samples were collected from 986 prevalent cases and 1,313 age-matched community controls and tested for presence of antibodies to Onchocerca volvulus, Toxocara canis, Toxoplasma gondii, Plasmodium falciparum, Taenia solium and HIV. Exposure (seropositivity) to Onchocerca volvulus (OR = 1.98; 95%CI: 1.52–2.58, p<0.001), Toxocara canis (OR = 1.52; 95%CI: 1.23–1.87, p<0.001), Toxoplasma gondii (OR = 1.28; 95%CI: 1.04–1.56, p = 0.018) and higher antibody levels (top tertile) to Toxocara canis (OR = 1.70; 95%CI: 1.30–2.24, p<0.001) were associated with an increased prevalence of ACE. Exposure to multiple infections was common (73.8% of cases and 65.5% of controls had been exposed to two or more infections), and for T. gondii and O. volvulus co-infection, their combined effect on the prevalence of ACE, as determined by the relative excess risk due to interaction (RERI), was more than additive (T. gondii and O. volvulus, RERI = 1.19). The prevalence of T. solium antibodies was low (2.8% of cases and 2.2% of controls) and was not associated with ACE in the study areas. Conclusion This study investigates how the degree of exposure to parasites and multiple parasitic infections are associated with ACE and may explain conflicting results obtained when only seropositivity is considered. The findings from this study should be further validated.

Seroprevalence of antibodies against Taenia solium cysticerci among refugees resettled in United States

Cysticercosis is an infection caused by a pork tapeworm that creates cysts in different areas of the human body. Sometimes, these parasites can get into the infected patient’s brain and lead to epilepsy or other neurologic disorders. Cysticercosis is most common in developing countries that have poor sanitation and where pigs feed on human waste; however, cases in the United States are increasing. A recent study found that many refugees who settle in the United States, including those from Burma, Laos, Burundi, and Bhutan, have been infected with the tapeworm. The occurrence of cysticercosis among these groups has clinical and public health implications because US physicians might not be familiar with this disease and its symptoms. Cysticercosis should be suspected in refugees who have seizures, headache, or other unexplained neurologic symptoms. Physicians should also be aware that treatment for intestinal parasites, routinely given to refugees before they leave their homeland, can cause serious neurologic reactions in those already infected with the tapeworm.

Taenia solium Tapeworm Infection, Oregon, 2006-2009.

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.

Recombinant Protein- and Synthetic Peptide-Based Immunoblot Test for Diagnosis of Neurocysticercosis

ABSTRACT One of the most well-characterized tests for diagnosing neurocysticercosis (NCC) is the enzyme-linked immunoelectrotransfer blot (EITB) assay developed at the CDC, which uses lentil lectin-bound glycoproteins (LLGP) extracted from Taenia solium cysticerci. Although the test is very reliable, the purification process for the LLGP antigens has been difficult to transfer to other laboratories because of the need for expensive equipment and technical expertise. To develop a simpler assay, we previously purified and cloned the diagnostic glycoproteins in the LLGP fraction. In this study, we evaluated three representative recombinant or synthetic antigens from the LLGP fraction, individually and in different combinations, using an immunoblot assay (recombinant EITB). Using a panel of 249 confirmed NCC-positive and 401 negative blood serum samples, the sensitivity of the recombinant EITB assay was determined to be 99% and the specificity was 99% for diagnosing NCC. We also tested a panel of 239 confirmed NCC-positive serum samples in Lima, Peru, and found similar results. Overall, our data show that the performance characteristics of the recombinant EITB assay are comparable to those of the LLGP-EITB assay. This new recombinant- and synthetic antigen-based assay is sustainable and can be easily transferred to other laboratories in the United States and throughout the world.