Epidemiologic aspects of the relationship between infection with Leishmania chagasi and development of clinical visceral leishmaniasis (VL) were studied in all children < 11 years old in a defined, endemic, rural area of the state of Ceará in northeast Brazil. Antileishmanial antibodies were measured in the same subjects by ELISA on six occasions between May 1987 and August 1989. Seroconversion was documented during this period in 108 children, with a cumulative annual incidence of 4.6%. Twelve (11.1%) of these children developed VL. Age < 4 years, hematocrit < 33%, and living in the mountains predicted the development of clinically apparent VL after seroconversion. Despite a high percentage of dogs serologically positive in the region (38%), there was no increased risk of infection for children living in the same household with dogs. Since children in households with a prior case of VL had a threefold increased risk of infection, human-sandfly-human transmission might have been important.

The serodiagnosis of Strongyloides stercoralis infection by enzyme-linked immunosorbent assays based on crude antigen (CrAg-ELISA), while useful, has been limited by the reliance on crude parasite extracts. Newer techniques such as the luciferase immunoprecipitation system assay (LIPS), based on a 31-kDa recombinant antigen (termed NIE) from S. stercoralis and/or the recombinant antigen S. stercoralis immunoreactive antigen (SsIR), or the NIE-ELISA have shown promise in controlled settings. We compared each of these serologic assays in individuals from both regions of the world in which S. stercoralis is endemic and those in which it is not. A comprehensive stool evaluation (sedimentation concentration, Baermann concentration with charcoal cultures, agar plate, and Harada-Mori) and four different serologic techniques using CrAg-ELISA or recombinant NIE-ELISA as well as LIPS using NIE alone or in combination with a second recombinant antigen (NIE/SsIR-LIPS) were compared among individuals with parasitologically proven infection (n ‫؍‬ 251) and healthy controls from regions of the world in which the infection is nonendemic (n ‫؍‬ 11). Accuracy was calculated for each assay. The prevalence of S. stercoralis infection was 29.4% among Argentinean stool samples (n ‫؍‬ 228). Sedimentation concentration and Baermann were the most sensitive stool-based methods. NIE-LIPS showed the highest sensitivity (97.8%) and specificity (100%) of the serologic assays. The calculated negative predictive value was highest for both the NIE-LIPS and CrAg-ELISA (>97%) irrespective of disease prevalence. No cross-reactivity with soil-transmitted helminths was noted. NIE-LIPS compares favorably against the current CrAg-ELISA and stool evaluation, providing additional accuracy and ease of performance in the serodiagnosis of S. stercoralis infections irrespective of disease prevalence.

Infection with Strongyloides stercoralis is typically asymptomatic in immunocompetent hosts, despite chronic infection. In contrast, immunocompromised hosts such as solid organ transplant recipients are at risk for hyperinfection syndrome and/or disseminated disease, frequently resulting in fatal outcomes. Infection in these recipients may result from reactivation of latent infection or infection through transmission from an infected donor. We describe the Centers for Disease Control and Prevention's experience with seven clusters of donor-derived infection from 2009 to 2013. Six of the seven (86%) donors were born in Latin America; donor screening was not performed prior to organ transplantation in any of these investigations. Eleven of the 20 (55%) organ recipients were symptomatic, two of whom died from complications of strongyloidiasis. We also describe the New York Organ Donor Network (NYODN) experience with targeted donor screening from 2010 to 2013. Of the 233 consented potential donors tested, 10 tested positive for Strongyloides antibody; and 18 organs were transplanted. The majority (86%) of the donors were born in Central or South America. Fourteen recipients received prophylaxis after transplantation; no recipients developed strongyloidiasis. The NYODN experience provides evidence that when targeted donor screening is performed prior to transplantation, donor-derived infection can be averted in recipients.

Strongyloides stercoralis is a widely distributed parasite that infects 30 to 100 million people worldwide. In the United States strongyloidiasis is recognized as an important infection in immigrants and refugees. Public health and commercial reference laboratories need a simple and reliable method for diagnosis of strongyloidiasis to identify and treat cases and to prevent transmission. The recognized laboratory test of choice for diagnosis of strongyloidiasis is detection of disease specific antibodies, most commonly using a crude parasite extract for detection of IgG antibodies. Recently, a luciferase tagged recombinant protein of S. stercoralis, Ss-NIE-1, has been used in a luciferase immunoprecipitation system (LIPS) to detect IgG and IgG4 specific antibodies. To promote wider adoption of immunoassays for strongyloidiasis, we used the Ss-NIE-1 recombinant antigen without the luciferase tag and developed ELISA and fluorescent bead (Luminex) assays to detect S. stercoralis specific IgG4. We evaluated the assays using well-characterized sera from persons with or without presumed strongyloidiasis. The sensitivity and specificity of Ss-NIE-1 IgG4 ELISA were 95% and 93%, respectively. For the IgG4 Luminex assay, the sensitivity and specificity were 93% and 95%, respectively. Specific IgG4 antibody decreased after treatment in a manner that was similar to the decrease of specific IgG measured in the crude IgG ELISA. The sensitivities of the Ss-NIE-1 IgG4 ELISA and Luminex assays were comparable to the crude IgG ELISA but with improved specificities. However, the Ss-NIE-1 based assays are not dependent on native parasite materials and can be performed using widely available laboratory equipment. In conclusion, these newly developed Ss-NIE-1 based immunoassays can be readily adopted by public health and commercial reference laboratories for routine screening and clinical diagnosis of S. stercoralis infection in refugees and immigrants in the United States.

The detection of pathogen-specific antibodies remains a cornerstone of clinical diagnostics. Yet, many test exhibit undesirable performance or are completely lacking. Given this, we developed serum epitope repertoire analysis (SERA), a method to rapidly discover conserved, pathogen-specific antigens and their epitopes, and applied it to develop an assay for Chagas disease caused by the protozoan parasite Trypanosoma cruzi. Antibody binding peptide motifs were identified from 28 Chagas repertoires using a bacterial display random 12-mer peptide library and next-generation sequencing (NGS). Thirty-three motifs were selected and mapped to candidate Chagas antigens. In a blinded validation set (n = 72), 30/30 Chagas were positive, 30/30 non-Chagas were negative, and 1/12 Leishmania sp. was positive. After unblinding, a Leishmania cross-reactive epitope was identified and removed from the panel. The Chagas assay exhibited 100% sensitivity (30/30) and specificity (90/90) in a second blinded validation set including individuals with other parasitic infections. Amongst additional epitope repertoires with unknown Chagas serostatus, assay specificity was 99.8% (998/1000). Thus, the Chagas assay achieved a combined sensitivity and specificity equivalent or superior to diagnostic algorithms that rely on three separate tests to achieve high specificity. NGS-based serology via SERA provides an effective approach to discover antigenic epitopes and develop high performance multiplex serological assays.

The clinical spectrum of human disease caused by the roundworms Toxocara canis and Toxocara cati ranges from visceral and ocular larva migrans to covert toxocariasis. The parasite is not typically recovered in affected tissues, so detection of parasite-specific antibodies is usually necessary for establishing a diagnosis. The most reliable immunodiagnostic methods use the Toxocara excretory-secretory antigens (TES-Ag) in ELISA formats to detect Toxocara-specific antibodies. To eliminate the need for native parasite materials, we identified and purified immunodiagnostic antigens using 2D gel electrophoresis followed by electrospray ionization mass spectrometry. Three predominant immunoreactive proteins were found in the TES; all three had been previously described in the literature: Tc-CTL-1, Tc-TES-26, and Tc-MUC-3. We generated Escherichia coli expressed recombinant proteins for evaluation in Luminex based immunoassays. We were unable to produce a functional assay with the Tc-MUC-3 recombinant protein. Tc-CTL-1 and Tc-TES-26 were successfully coupled and tested using defined serum batteries. The use of both proteins together generated better results than if the proteins were used individually. The sensitivity and specificity of the assay for detecting visceral larval migrans using Tc-CTL-1 plus Tc-TES-26 was 99% and 94%, respectively; the sensitivity for detecting ocular larval migrans was 64%. The combined performance of the new assay was superior to the currently available EIA and could potentially be employed to replace current assays that rely on native TES-Ag.

These data indicate that toroviruses, alone or in combination with enteroaggregative E. coli, may play a pathogenic role in acute and possibly persistent diarrhea. Further studies are warranted to determine the etiologic role of toroviruses in gastroenteritis.

BackgroundForeign-born, HIV-infected persons are at risk for sub-clinical parasitic infections acquired in their countries of origin. The long-term consequences of co-infections can be severe, yet few data exist on parasitic infection prevalence in this population.Methodology/Principal FindingsThis cross-sectional study evaluated 128 foreign-born persons at one HIV clinic. We performed stool studies and serologic testing for strongyloidiasis, schistosomiasis, filarial infection, and Chagas disease based on the patient's country of birth. Eosinophilia and symptoms were examined as predictors of helminthic infection. Of the 128 participants, 86 (67%) were male, and the median age was 40 years; 70 were Mexican/Latin American, 40 African, and 18 from other countries or regions. Strongyloides stercoralis antibodies were detected in 33/128 (26%) individuals. Of the 52 persons from schistosomiasis-endemic countries, 15 (29%) had antibodies to schistosome antigens; 7 (47%) had antibodies to S. haematobium, 5 (33%) to S. mansoni, and 3 (20%) to both species. Stool ova and parasite studies detected helminths in 5/85 (6%) persons. None of the patients tested had evidence of Chagas disease (n = 77) or filarial infection (n = 52). Eosinophilia >400 cells/mm3 was associated with a positive schistosome antibody test (OR 4.5, 95% CI 1.1–19.0). The only symptom significantly associated with strongyloidiasis was weight loss (OR 3.1, 95% CI 1.4–7.2).Conclusions/SignificanceGiven the high prevalence of certain helminths and the potential lack of suggestive symptoms and signs, selected screening for strongyloidiasis and schistosomiasis or use of empiric antiparasitic therapy may be appropriate among foreign-born, HIV-infected patients. Identifying and treating helminth infections could prevent long-term complications.