Lessons learned from the implementation of integrated serosurveillance of communicable diseases in the Americas.

Objective: Systematize the experience and identify challenges and lessons learned in the implementation of an initiative for integrated serosurveillance of communicable diseases using a multiplex bead assay in countries of the Americas. Methods: Documents produced in the initiative were compiled and reviewed. These included concept notes, internal working papers, regional meetings reports, and survey protocols from the three participating countries (Mexico, Paraguay, and Brazil) and two additional countries (Guyana and Guatemala) where serology for several communicable diseases was included in neglected tropical diseases surveys. Information was extracted and summarized to describe the experience and the most relevant challenges and lessons learned. Results: Implementing integrated serosurveys requires interprogrammatic and interdisciplinary work teams for the design of survey protocols to respond to key programmatic questions aligned to the needs of the countries. Valid laboratory results are critical and rely on the standardized installment and roll-out of laboratory techniques. Field teams require adequate training and supervision to properly implement survey procedures. The analysis and interpretation of serosurveys results should be antigen-specific, contextualizing the responses for each disease, and triangulated with programmatic and epidemiological data for making decisions tailored to specific population socioeconomic and ecologic contexts. Conclusions: Integrated serosurveillance as a complementary tool for functional epidemiological surveillance systems is feasible to use and key components should be considered: political engagement, technical engagement, and integrated planning. Aspects such as designing the protocol, selecting target populations and diseases, laboratory capacities, anticipating the capacities to analyze and interpret complex data, and how to use it are key.

Development of a Bead-Based Multiplex Assay for Use in Multianalyte Screening and Surveillance of HIV, Viral Hepatitis, Syphilis, and Herpes.

Diagnostic assays that can simultaneously determine the presence of infection with multiple pathogens are key for diagnosis and surveillance. Current multiplex diagnostic assays are complex and often have limited availability. We developed a simple, multianalyte, pathogen detection assay for screening and serosurveillance using the Luminex Magpix platform that is high throughput and can be helpful in monitoring multiple diseases. The Luminex bead-based 10-plex immunoassay for the detection of HIV-1, HIV-2, Treponema pallidum, hepatitis B virus (HBV), hepatitis C virus (HCV), herpes simplex virus 1 (HSV-1), and HSV-2 infections was accomplished by coupling beads with specific antigens to detect IgG antibodies in plasma or serum samples. Each coupled antigen was systematically optimized, and the performance was evaluated using a panel of well-characterized specimens (n = 417) that contained antibodies to HIV-1, HIV-2, T. pallidum, HBV, HCV, HSV-1, and HSV-2. The multiplex assay had a sensitivity of 92.2% (95% Clopper-Pearson confidence interval [CI], 90.2 to 94.0%) and a specificity of 98.1% (95% CI, 97.6 to 98.7%). The sensitivities and specificities for disease-specific biomarker detection ranged from 68.7 to 100% and 95.6 to 100%, respectively. The results showed that the 10-plex immunoassay had an overall agreement of 96.7% (95% CI, 96.7 to 97.3%) with reference tests and a corresponding kappa value of 0.91 (95% CI, 0.90 to 0.93). Kappa values for the individual pathogens ranged from 0.69 to 1.00. The assay is robust and allows the simultaneous detection of antibodies to multiple antigens using a small sample volume in a high-throughput format. This assay has the potential to simplify disease surveillance by providing an alternative to expensive and highly specialized individual tests.

Parasitic Disease Surveillance, Mississippi, USA.

Surveillance for soil-transmitted helminths, strongyloidiasis, cryptosporidiosis, and giardiasis was conducted in Mississippi, USA. PCR performed on 224 fecal samples for all soil-transmitted helminths and on 370 samples for only Necator americanus and Strongyloides stercoralis identified 1 S. stercoralis infection. Seroprevalences were 8.8% for Toxocara, 27.4% for Cryptosporidium, 5.7% for Giardia, and 0.2% for Strongyloides parasites.

Vaccination coverage survey and seroprevalence among forcibly displaced Rohingya children, Cox's Bazar, Bangladesh, 2018: A cross-sectional study.

BACKGROUND: During August 2017-January 2018, more than 700,000 forcibly displaced Rohingyas crossed into Cox's Bazar, Bangladesh. In response to measles and diphtheria cases, first documented in September and November 2017, respectively, vaccination campaigns targeting children <15 years old were mobilized during September 2017-March 2018. However, in a rapidly evolving emergency situation, poor sanitation, malnutrition, overcrowding, and lack of access to safe water and healthcare can increase susceptibility to infectious diseases, particularly among children. We aimed to estimate population immunity to vaccine-preventable diseases (VPDs) after vaccination activities in the camps to identify any remaining immunity gaps among Rohingya children. METHODS AND FINDINGS: We conducted a cross-sectional serologic and vaccination coverage survey in Nayapara Registered Refugee Camp ("Nayapara") and makeshift settlements (MSs) April 28, 2018 to May 31, 2018, among 930 children aged 6 months to 14 years. MSs are informal, self-settled areas with a population of more than 850,000, the majority of whom arrived after August 2017, whereas Nayapara is a registered camp and has better infrastructure than MSs, including provision of routine immunization services. Households were identified using simple random sampling (SRS) in Nayapara and multistage cluster sampling in MSs (because household lists were unavailable). Dried blood spots (DBSs) were collected to estimate seroprotection against measles, rubella, diphtheria, and tetanus, using Luminex multiplex bead assay (MBA). Caregiver interviews assessed vaccination campaign participation using vaccination card or recall. In Nayapara, 273 children aged 1 to 6 years participated; 46% were female and 88% were registered refugees. In MSs, 358 children aged 1 to 6 years and 299 children aged 7 to 14 years participated; 48% of all children in MSs were female, and none were registered refugees. In Nayapara, estimated seroprotection among 1- to 6-year-olds was high for measles, rubella, diphtheria, and tetanus (91%-98%; 95% confidence interval [CI] 87%-99%); children >6 years were not assessed. In MSs, measles seroprotection was similarly high among 1- to 6-year-olds and 7- to 14-year-olds (91% [95% CI 86%-94%] and 99% [95% CI 96%-100%], respectively, p < 0.001). Rubella and diphtheria seroprotection in MSs were significantly lower among 1- to 6-year-olds (84% [95% CI 79%-88%] and 63% [95% CI 56%-70%]) compared to 7- to 14-year-olds (96% [95% CI 90%-98%] and 77% [95% CI 69%-84%]) (p < 0.001). Tetanus seroprevalence was similar among 1- to 6-year-olds and 7- to 14-year-olds (76% [95% CI 69%-81%] and 84% [95% CI 77%-89%], respectively; p = 0.07). Vaccination campaign coverage was consistent with seroprotection in both camps. However, nonresponse, the main limitation of the study, may have biased the seroprotection and campaign coverage results. CONCLUSIONS: In this study, we observed that despite multiple vaccination campaigns, immunity gaps exist among children in MSs, particularly for diphtheria, which requires serial vaccinations to achieve maximum protection. Therefore, an additional tetanus-diphtheria campaign may be warranted in MSs to address these remaining immunity gaps. Rapid scale-up and strengthening of routine immunization services to reach children and to deliver missed doses to older children is also critically needed to close immunity gaps and prevent future outbreaks.

Screening for malaria antigen and anti-malarial IgG antibody in forcibly-displaced Myanmar nationals: Cox's Bazar district, Bangladesh, 2018.

BACKGROUND: Several refugee settlements in Bangladesh have provided housing and medical care for the forcibly-displaced Myanmar nationals (FDMN, also known as Rohingya) population. The identification of malaria infection status in the refugee settlements is useful in treating infected persons and in developing malaria prevention recommendations. Assays for Plasmodium antigens and human IgG against Plasmodium parasites can be used as indicators to determine malaria infection status and exposure. METHODS: Dried blood spot (DBS) samples (N = 1239) from a household survey performed April-May 2018 in three settlements in Cox's Bazar district, Bangladesh were utilized for a sample population of children from ages 1-14 years of age. The samples were tested using a bead-based multiplex antigen assay for presence of the pan-Plasmodium antigen aldolase as well as Plasmodium falciparum histidine rich protein 2 (HRP2). A bead-based multiplex assay was also used to measure human IgG antibody response to P. falciparum, Plasmodium malariae, and Plasmodium vivax merozoite surface protein 1 antigen (MSP1) isoforms, and P. falciparum antigens LSA1, CSP, and GLURP-R0. RESULTS: There were no detectable Plasmodium antigens in any samples, suggesting no active malaria parasite infections in the tested children. IgG seroprevalence was highest to P. vivax (3.1%), but this was not significantly different from the percentages of children antibody responses to P. falciparum (2.1%) and P. malariae (1.8%). The likelihood of an anti-Plasmodium IgG response increased with age for all three malaria species. Evidence of exposure to any malaria species was highest for children residing 8-10 months in the settlements, and was lower for children arriving before and after this period of time. CONCLUSIONS: Absence of Plasmodium antigen in this population provides evidence that children in these three Bangladeshi refugee settlements did not have malaria at time of sampling. Higher rates of anti-malarial IgG carriage from children who were leaving Myanmar during the malaria high-transmission season indicate these migrant populations were likely at increased risk of malaria exposure during their transit.

Biannual versus annual mass azithromycin distribution and malaria seroepidemiology among preschool children in Niger: a sub-study of a cluster randomized trial.

BACKGROUND: Biannual mass azithromycin administration to preschool children reduces all-cause mortality, but the mechanism for the effect is not understood. Azithromycin has activity against malaria parasites, and malaria is a leading cause of child mortality in the Sahel. The effect of biannual versus annual azithromycin distribution for trachoma control on serological response to merozoite surface protein 1 (MSP-119), a surrogate for malaria incidence, was evaluated among children in Niger. METHODS: Markers of malaria exposure were measured in two arms of a factorial randomized controlled trial designed to evaluate targeted biannual azithromycin distribution to children under 12 years of age compared to annual azithromycin to the entire community for trachoma control (N = 12 communities per arm). Communities were treated for 36 months (6 versus 3 distributions). Dried blood spots were collected at 36 months among children ages 1-5 years, and MSP-119 antibody levels were assessed using a bead-based multiplex assay to measure malaria seroprevalence. RESULTS: Antibody results were available for 991 children. MSP-119 seropositivity was 62.7% in the biannual distribution arm compared to 68.7% in the annual arm (prevalence ratio 0.91, 95% CI 0.83 to 1.00). Mean semi-quantitative antibody levels were lower in the biannual distribution arm compared to the annual arm (mean difference - 0.39, 95% CI - 0.05 to - 0.72). CONCLUSIONS: Targeted biannual azithromycin distribution was associated with lower malaria seroprevalence compared to that in a population that received annual distribution. Trial Registration Clinicaltrials.gov NCT00792922.

Evaluation of Multiplex-Based Antibody Testing for Use in Large-Scale Surveillance for Yaws: a Comparative Study.

WHO has targeted yaws for global eradication by 2020. The program goals are to interrupt the transmission in countries where yaws is endemic and to certify countries as yaws free where yaws was endemic in the past. No new rapid plasmin reagin (RPR) seroreactivity in young children is required for certification of elimination at a country level. We sought to evaluate whether antibody responses to specific treponemal antigens measured in a high-throughput multiplex bead array (MBA) assay differentiate past versus current infection and whether a nontreponemal lipoidal antigen test can be incorporated into the MBA. Serum and dried blood spot specimens collected for yaws surveillance projects in Ghana, Vanuatu, and Papua New Guinea (PNG) were run on MBA to measure antibodies against recombinant p17 (rp17) and treponemal membrane protein A (TmpA) treponemal antigens. Results were compared to standard treponemal laboratory (TPPA or TPHA [TPP(H)A]) and quantitative RPR test data. Of 589 specimens, 241 were TPP(H)A(+)/RPR(+), 88 were TPP(H)A(+)/RPR(-), 6 were TPP(H)A(-)/RPR(+), and 254 were negative for both tests. Compared to TPP(H)A, reactive concordance of rp17 was 93.7%, while reactive concordance of TmpA was only 81.9%. TmpA-specific reactivity showed good correlation with RPR titers (R(2) = 0.41; P < 0.0001). IgG responses to the lipoidal antigen used in RPR testing (cardiolipin) were not detected in the MBA. Our results suggest that TmpA can be used as a treponemal antigen marker for recent or active infection and potentially replace RPR in a high-throughput multiplex tool for large-scale yaws surveillance.

Frequency of IFNγ-producing T cells correlates with seroreactivity and activated T cells during canine Trypanosoma cruzi infection.

Vaccines to prevent Trypanosoma cruzi infection in humans or animals are not available, and in many settings, dogs are an important source of domestic infection for the insect vector. Identification of infected canines is crucial for evaluating peridomestic transmission dynamics and parasite control strategies. As immune control of T. cruzi infection is dependent on humoral and cell-mediated immune responses, we aimed to define a serodiagnostic assay and T cell phenotypic markers for identifying infected dogs and studying the canine T. cruzi-specific immune response. Plasma samples and peripheral blood mononuclear cells (PBMCs) were obtained from forty-two dogs living in a T. cruzi-endemic region. Twenty dogs were known to be seropositive and nine seronegative by conventional serologic tests two years prior to our study. To determine canine seroreactivity, we tested sera or plasma samples in a multiplex bead array against eleven recombinant T. cruzi proteins. Ninety-four percent (17/18) of dogs positive by multiplex serology were initially positive by conventional serology. The frequency of IFNγ-producing cells in PBMCs responding to T. cruzi correlated to serological status, identifying 95% of multiplex seropositive dogs. Intracellular staining identified CD4+ and CD8+ T cell populations as the sources of T. cruzi lysate-induced IFNγ. Low expression of CCR7 and CD62L on CD4+ and CD8+ T cells suggested a predominance of effector/effector memory T cells in seropositive canines. These results are the first, to our knowledge, to correlate T. cruzi-specific antibody responses with T cell responses in naturally infected dogs and validate these methods for identifying dogs exposed to T. cruzi.

shinyMBA: a novel R shiny application for quality control of the multiplex bead assay for serosurveillance studies.

The multiplex bead assay (MBA) based on Luminex xMAP technology can be used as a tool to measure seroprevalence as part of population immunity evaluations to multiple antigens in large-scale serosurveys. However, multiplexing several antigens presents challenges for quality control (QC) assessments of the data because multiple parameters must be evaluated for each antigen. MBA QC parameters include monitoring bead counts and median fluorescence intensity (MFI) for each antigen in plate wells, and performance of assay controls included on each plate. Analyzing these large datasets to identify plates failing QC standards presents challenges for many laboratories. We developed a novel R Shiny application, shinyMBA, to expedite the MBA QC processes and reduce the risk of user error. The app allows users to rapidly merge multi-plate assay outputs to evaluate bead count, MFI, and performance of assay controls using statistical process control charts for all antigen targets simultaneously. The utility of the shinyMBA application and its various outputs are demonstrated using data from 32 synthetic xPONENT files with 3 multiplex antigens and two population serosurveillance studies that evaluated 1200 and 3871 samples, respectively, for 20 multiplexed antigens. The shinyMBA open-source code is available for download and modification at https://github.com/CDCgov/shinyMBA . Incorporation of shinyMBA into Luminex serosurveillance workflows can vastly improve the speed and accuracy of QC processes.

Anti-filarial antibodies are sensitive indicators of lymphatic filariasis transmission and enable identification of high-risk populations and hotspots.

OBJECTIVES: Circulating filarial antigen (Ag) is used by elimination programs to monitor lymphatic filariasis (LF) transmission; however, antifilarial antibodies (Ab) may be more sensitive than Ag for detecting LF. Our objectives were to describe Ab seroprevalence, identify risk factors for Ab seropositivity, investigate age-specific associations between Ag and Ab, and evaluate geographic clustering of seropositivity. METHODS: Community-based serosurveys of participants aged ≥5 years were conducted in 35 primary sampling units (PSUs). Ag-positivity was detected using Alere™ Filariasis Test Strips and Ab-seropositivity using multiplex bead assays. Seroprevalence was adjusted for study design. RESULTS: Of 3795 participants (range:5-90 years), adjusted prevalence for Ag, Bm14 Ab, Wb123 Ab, and Bm33 Ab were 3.7% (n=117), 20.3% (n=583), 32.2% (n=987), and 51.0% (n=1659), respectively. Male sex, older age, and residents of suspected hotspots had higher odds of seropositivity to all seromarkers. Seroprevalence was lower in 5-9-year-olds vs ≥10-year-olds (P<0.001). Clustering was significantly higher in households (intra-cluster correlation for Ag:0.45; Bm14 Ab:0.32; Bm33 Ab:0.31; Wb123 Ab:0.29) compared to PSUs or region. CONCLUSIONS: Abs enabled identification of risk factors for seropositivity and geographical clustering to inform targeted interventions for LF programmes. Further research is needed to define Ab thresholds for active versus past infection and elimination targets.

Treponemal Antibody Seroprevalence Using a Multiplex Bead Assay from Samples Collected during the 2018 Nigeria HIV/AIDS Indicator and Impact Survey: Searching for Yaws in Nigeria.

Yaws is a chronic, relapsing disease of skin, bone, and cartilage caused by Treponema pallidum subsp. pertenue. Yaws was last reported in Nigeria in 1996, although neighboring countries have recently reported cases. We investigated serological evidence for yaws among children aged 0-14 years in Nigeria by measuring antibodies to the treponemal antigens rp17 and TmpA in blood specimens from a 2018 nationally representative HIV survey using a multiplex bead assay. The presence of antibodies to both antigens ("double positive") likely reflects current or recent treponemal infection. Overall, 1.9% (610/31,549) of children had anti-TmpA antibodies, 1.5% (476/31,549) had anti-rp17 antibodies, and 0.1% (39/31,549) were double positive. Among households, 0.5% (84/18,021) had a double-positive child, with a clustering of double-positive children. Although numbers are low, identification of antibodies to both TmpA and rp17 may warrant investigation, including more granular epidemiologic and clinical data, to assess the potential for continuing yaws transmission in Nigerian children.

Tetanus and Diphtheria Seroprotection among Children Younger Than 15 Years in Nigeria, 2018: Who Are the Unprotected Children?

Serological surveys provide an objective biological measure of population immunity, and tetanus serological surveys can also assess vaccination coverage. We undertook a national assessment of immunity to tetanus and diphtheria among Nigerian children aged <15 years using stored specimens collected during the 2018 Nigeria HIV/AIDS Indicator and Impact Survey, a national cross-sectional household-based survey. We used a validated multiplex bead assay to test for tetanus and diphtheria toxoid-antibodies. In total, 31,456 specimens were tested. Overall, 70.9% and 84.3% of children aged <15 years had at least minimal seroprotection (≥0.01 IU/mL) against tetanus and diphtheria, respectively. Seroprotection was lowest in the north west and north east zones. Factors associated with increased tetanus seroprotection included living in the southern geopolitical zones, urban residence, and higher wealth quintiles (p < 0.001). Full seroprotection (≥0.1 IU/mL) was the same for tetanus (42.2%) and diphtheria (41.7%), while long-term seroprotection (≥1 IU/mL) was 15.1% for tetanus and 6.0% for diphtheria. Full- and long-term seroprotection were higher in boys compared to girls (p < 0.001). Achieving high infant vaccination coverage by targeting specific geographic areas and socio-economic groups and introducing tetanus and diphtheria booster doses in childhood and adolescence are needed to achieve lifelong protection against tetanus and diphtheria and prevent maternal and neonatal tetanus.

Diphtheria and tetanus seroepidemiology among children in Ukraine, 2017.

BACKGROUND: The drastic decline of Ukraine's immunization coverage since 2009 led to concerns about potential resurgence diphtheria and tetanus, along with other vaccine-preventable diseases. METHODS: To assess population immunity against diphtheria and tetanus, we tested specimens from the serosurvey conducted in 2017 among children born in 2006-2015, the birth cohorts targeted by the nationwide outbreak response immunization following a circulating vaccine-derived poliovirus type 1 outbreak in Zakarpattya province in 2015. We surveyed four regions of Ukraine, using cluster sampling in Zakarpattya, Sumy, and Odessa provinces and simple random sampling in Kyiv City. We tested serum specimens for IgG antibodies against diphtheria and tetanus, using microbead assays (MBA). We estimated seroprevalence and calculated 95% confidence intervals. We also obtained information on the immunization status of surveyed children. RESULTS: Seroprevalence of ≥0.1 IU/mL diphtheria antibodies was <80% in all survey sites (50.0%-79.2%). Seroprevalence of ≥0.1 IU/mL tetanus antibodies was ≥80% in Sumy, Kyiv City, and Odessa (80.2%-89.1%) and 61.6% in Zakarpattya. Across the sites, the proportion of children vaccinated age-appropriately with diphtheria-tetanus-containing vaccines (DTCV) was 28.5%-57.4% among children born in 2006-2010 and 34.1%-54.3% among children born in 2011-2015. The proportion of recipients of <3 DTCV doses increased from 7.1%-16.7% among children born in 2006-2010 to 19.8%-38.6% among children born in 2011-2015, as did the proportion of recipients of zero DTCV doses (2.6%-8.8% versus 8.0%-14.0%, respectively). CONCLUSIONS: Protection against diphtheria among children born in 2006-2015 was suboptimal (<80%), particularly in Zakarpattya. Protection against tetanus was adequate (≥80%) except in Zakarpattya. Diphtheria-tetanus immunization status was suboptimal across all sites. Catch-up vaccination of unvaccinated/under-vaccinated children and other efforts to increase immunization coverage would close these immunity gaps and prevent the resurgence of diphtheria and tetanus in Ukraine, particularly in Zakarpattya.

High variation in immune responses and parasite phenotypes in naturally acquired Trypanosoma cruzi infection in a captive non-human primate breeding colony in Texas, USA.

Trypanosoma cruzi, the causative agent of human Chagas disease, is endemic to the southern region of the United States where it routinely infects many host species. The indoor/outdoor housing configuration used in many non-human primate research and breeding facilities in the southern of the USA provides the opportunity for infection by T. cruzi and thus provides source material for in-depth investigation of host and parasite dynamics in a natural host species under highly controlled and restricted conditions. For cynomolgus macaques housed at such a facility, we used a combination of serial blood quantitative PCR (qPCR) and hemoculture to confirm infection in >92% of seropositive animals, although each method alone failed to detect infection in >20% of cases. Parasite isolates obtained from 43 of the 64 seropositive macaques were of 2 broad genetic types (discrete typing units, (DTU's) I and IV); both within and between these DTU groupings, isolates displayed a wide variation in growth characteristics and virulence, elicited host immune responses, and susceptibility to drug treatment in a mouse model. Likewise, the macaques displayed a diversity in T cell and antibody response profiles that rarely correlated with parasite DTU type, minimum length of infection, or age of the primate. This study reveals the complexity of infection dynamics, parasite phenotypes, and immune response patterns that can occur in a primate group, despite being housed in a uniform environment at a single location, and the limited time period over which the T. cruzi infections were established.

No Serological Evidence of Trachoma or Yaws Among Residents of Registered Camps and Makeshift Settlements in Cox's Bazar, Bangladesh.

Successful achievement of global targets for elimination of trachoma as a public health problem and eradication of yaws will require control efforts to reach marginalized populations, including refugees. Testing for serologic evidence of transmission of trachoma and yaws in residents of registered camps and a Makeshift Settlement in Cox's Bazar District, Bangladesh, was added to a serosurvey for vaccine-preventable diseases (VPDs) conducted April-May 2018. The survey was primarily designed to estimate remaining immunity gaps for VPDs, including diphtheria, measles, rubella, and polio. Blood specimens from 1- to 14-year-olds from selected households were collected and tested for antibody responses against antigens from Treponema pallidum and Chlamydia trachomatis using a multiplex bead assay to evaluate for serologic evidence of the neglected tropical diseases (NTDs) yaws and trachoma, respectively. The prevalence of antibodies against two C. trachomatis antigens in children ranged from 1.4% to 1.5% for Pgp3 and 2.8% to 7.0% for CT694. The prevalence of antibody responses against both of two treponemal antigens (recombinant protein17 and treponemal membrane protein A) tested was 0% to 0.15% in two camps. The data are suggestive of very low or no transmission of trachoma and yaws, currently or previously, in children resident in these communities. This study illustrates how integrated serologic testing can provide needed data to help NTD programs prioritize limited resources.

Seroprevalence of chronic hepatitis B virus infection and immunity to measles, rubella, tetanus and diphtheria among schoolchildren aged 6-7 years old in the Solomon Islands, 2016.

The Western Pacific Region (WPR) established a goal to decrease chronic hepatitis B virus (HBV) infection among children to <1% and to achieve ≥95% hepatitis B vaccine birth dose (HepB-BD) and ≥95% three-dose (HepB3) coverage by 2017. In 2016, we conducted a national serosurvey in the Solomon Islands among 6-7-year-old school children to assess progress towards the control goal and immunity to measles, rubella, tetanus and diphtheria. Eighty schools were selected systematically proportional to their 6-7-year-old population; all 6-7-year-olds were enrolled. We collected basic demographic information and vaccination history. Children were tested for HBV surface antigen (HBsAg) using a rapid test, and for immunity to measles, rubella, tetanus, and diphtheria using a multiplex bead assay. In total, 1,249 out of 1,492 children (84%) were enrolled, among whom 1,169 (94%) underwent HBsAg testing and 1,156 (93%) provided dried blood spots. Almost 80% (n = 982) of enrolled children had vaccination cards, among whom 59% (n = 584) received a timely HepB-BD (within 24 hours of birth), 95% (n = 932) received HepB3, and >90% received vaccines for diphtheria, tetanus, and measles (rubella vaccine was not available at the time). HBsAg prevalence was 3.1% (95% confidence interval (CI): 2.0%-4.9%), with 55% of identified cases from one province. Among 982 children with vaccination cards, HBsAg prevalence was higher among children who had not received a timely HepB-BD and at least two HepB doses compared to those who had (4% vs. 2%). Of 1,156 tested children, immunoprotection estimates were 99% (95% CI: 98%-99%) for measles, 99% (95% CI: 97%-100%) for rubella, 85% (95% CI: 83%-87%) for tetanus, and 51% (95% CI: 47%-55%) for diphtheria. Improving timely HepB-BD coverage and maintaining high HepB3 coverage could help Solomon Islands reach the regional HBV control goal. Low immunity to tetanus and diphtheria suggests the need to introduce booster doses to ensure long-term protection.

Parasitic Infection Surveillance in Mississippi Delta Children.

Some recent studies suggest ongoing transmission of parasitic diseases in the American South; however, surveys in Mississippi children are lacking. We enrolled 166 children (median age 8 years, range 4-13 years) from the Mississippi Delta region and carried out multi-parallel real-time polymerase chain reaction (PCR) for Necator americanus, Ascaris lumbricoides, and Strongyloides stercoralis on their stool samples. Dried blood spots were obtained for multiplex serology antibody detection. Of 166 children, all reported having flushable toilets, 11% had soil exposure, and 34% had a pet dog or cat. None had prior diagnosis or treatment of parasitic disease. Multi-parallel real-time PCRs were negative on the 89 stool DNA extracts available for testing. Dried blood spot testing of all 166 children determined the seroprevalence of IgG antibodies to Toxocara spp. (3.6%), Cryptosporidium (2.4%), S. stercoralis, Fasciola hepatica, and Giardia duodenalis (all 0%). In conclusion, parasitic infections and exposure were scarce in this population. Larger studies of at-risk populations are needed.

Changes in Trypanosoma cruzi-specific immune responses after treatment: surrogate markers of treatment efficacy.

BACKGROUND: As many as 20 million people are living with Trypanosoma cruzi infection in Latin American, yet few receive any treatment. The major limitation in developing and evaluating potential new drugs for their efficacy is the lack of reliable tests to assess parasite burden and elimination. METHODS: Adults volunteers with chronic T. cruzi infection were evaluated clinically and stratified according to the Kuschnir classification. Individuals with group 0 and group 1 clinical status were treated with benznidazole (5 mg/kg per day for 30 days). The changes in T. cruzi-specific T cell and antibody responses, as well as in clinical status, were measured periodically over the 3-5-year follow-up period and were compared with pretreatment conditions and with values in an untreated control group. RESULTS: The frequency of peripheral interferon (IFN)-gamma-producing T cells specific for T. cruzi declined as early as 12 months after benznidazole treatment and subsequently became undetectable in a substantial proportion of treated subjects. In addition, decreases in antibody responses to a pool of recombinant T. cruzi proteins also decreased in many of these same subjects. The shift to negative IFN-gamma T cell responses was highly associated with an early increase in IFN-gamma-producing T cells with phenotypic features of effector/effector memory cells in a subset of subjects. Benznidazole treatment also resulted in an increase in naive and early differentiated memory-like CD8(+) T cells in a majority of subjects. CONCLUSIONS: Benznidazole treatment during chronic Chagas disease has a substantial impact on parasite-specific immune response that is likely indicative of treatment efficacy and cure.

Pgp3 seroprevalence and associations with active trachoma and ocular Chlamydia trachomatis infection in Malawi: cross-sectional surveys in six evaluation units.

BACKGROUND: Following one to five years of antibiotic mass drug administration (MDA) for the elimination of trachoma as a public health problem, programmes must conduct impact surveys to inform decisions on whether MDA is still needed. These decisions are currently based on the prevalence of trachomatous inflammation-follicular (TF), which, after MDA, correlates poorly with prevalence of ocular Chlamydia trachomatis infection. METHODOLOGY/PRINCIPAL FINDINGS: Impact surveys in six evaluation units (EUs) of Malawi were used as a platform to explore associations between the prevalence of TF, ocular C. trachomatis infection and anti-Pgp3 antibodies one year after the third annual round of MDA. Participants were examined for trachoma using the World Health Organization simplified grading system. Ocular swabs and dried blood spots (DBS) were collected from children aged 1-9 years. Swabs were tested for C. trachomatis DNA using GeneXpert. DBS were assayed for anti-Pgp3 antibodies using ELISA. EU-level prevalence of TF in children aged 1-9 years ranged from 4.7% (95% CI 3.4-6.3) to 7.2% (95% CI 5.8-8.9). Prevalence of C. trachomatis infection in children ranged from 0.1% (95% CI 0.0-0.6) to 0.7% (95% CI 0.3-1.3) while Pgp3 seroprevalence ranged from 6.9% (95% CI 5.4-8.6) to 12.0% (95% CI 10.1-14.0) and increased with age. CONCLUSIONS/SIGNIFICANCE: Based on current global policy, the prevalence of TF indicates that a further year of antibiotic MDA is warranted in four of six EUs yet the very low levels of infection cast doubt on the universal applicability of TF-based cut-offs for antibiotic MDA. Pgp3 seroprevalence was similar to that reported following MDA in other settings that have reached the elimination target however the predictive value of any particular level of seropositivity with respect to risk of subsequent infection recrudescence is, as yet, unknown.

Community-level chlamydial serology for assessing trachoma elimination in trachoma-endemic Niger.

BACKGROUND: Program decision-making for trachoma elimination currently relies on conjunctival clinical signs. Antibody tests may provide additional information on the epidemiology of trachoma, particularly in regions where it is disappearing or elimination targets have been met. METHODS: A cluster-randomized trial of mass azithromycin distribution strategies for trachoma elimination was conducted over three years in a mesoendemic region of Niger. Dried blood spots were collected from a random sample of children aged 1-5 years in each of 24 study communities at 36 months after initiation of the intervention. A multiplex bead assay was used to test for antibodies to two Chlamydia trachomatis antigens, Pgp3 and CT694. We compared seropositivity to either antigen to clinical signs of active trachoma (trachomatous inflammation-follicular [TF] and trachomatous inflammation-intense [TI]) at the individual and cluster level, and to ocular chlamydia prevalence at the community level. RESULTS: Of 988 children with antibody data, TF prevalence was 7.8% (95% CI 6.1 to 9.5) and TI prevalence was 1.6% (95% CI 0.9 to 2.6). The overall prevalence of antibody positivity to Pgp3 was 27.2% (95% CI 24.5 to 30), and to CT694 was 23.7% (95% CI 21 to 26.2). Ocular chlamydia infection prevalence was 5.2% (95% CI 2.8 to 7.6). Seropositivity to Pgp3 and/or CT694 was significantly associated with TF at the individual and community level and with ocular chlamydia infection and TI at the community level. Older children were more likely to be seropositive than younger children. CONCLUSION: Seropositivity to Pgp3 and CT694 correlates with clinical signs and ocular chlamydia infection in a mesoendemic region of Niger. TRIAL REGISTRATION: ClinicalTrials.gov NCT00792922.