Last data update: Apr 22, 2024. (Total: 46599 publications since 2009)
Records 1-30 (of 67 Records) |
Query Trace: Martin DL [original query] |
---|
Serological responses to trachoma antigens prior to the start of mass drug administration: Results from population-based baseline surveys, North Darfur, Sudan
Sanders AM , Elshafie BE , Abdalla Z , Simmons C , Goodhew EB , Gonzalez TA , Nute AW , Mohammed A , Callahan EK , Martin DL , Nash SD . Am J Trop Med Hyg 2024 After years of programmatic inaccessibility, in 2019-2020 the Sudan Federal Ministry of Health Trachoma Control Program conducted population-based trachoma surveys in three localities (districts) in North Darfur state, Sudan. These baseline surveys were to determine the prevalence of trachomatous inflammation-follicular (TF) among children aged 1-9 years and to further use serological markers to understand the historical trachoma burden within this mass drug administration (MDA)-naive area. Trained and certified graders collected trachoma clinical data, and trained nurses collected dried blood spot (DBS) samples. The DBSs were assayed on a multiplex bead array for antibody responses to the Chlamydia trachomatis antigens Pgp3 and CT694. Across the three localities, 3,613 individuals aged 1-9 years and 3,542 individuals aged ≥15 years were examined for clinical signs, and 8,322 DBSs were collected. The prevalence of TF among children aged 1-9 years was endemic (≥5%) in two localities (El Seraif, 15.6%, and Saraf Omrah, 11.0%) and below the TF elimination threshold (<5%) in the third (Kotom, 1.4%). The Pgp3 seroprevalence among children aged 1-9 years was 34.1% in El Seraif, 35.0% in Saraf Omrah, and 11.0% in Kotom. Locality prevalence results were similar for Pgp3 and CT694. Seroprevalence increased with age in all three localities. Serological data collected within these surveys demonstrate that all three localities have had a long history of exposure to Chlamydia trachomatis and that two of the three localities require MDA to reach elimination as a public health problem threshold. |
Seroreversion to chlamydia trachomatis Pgp3 antigen among children in a hyperendemic region of Amhara, Ethiopia
Tedijanto C , Aragie S , Gwyn S , Wittberg DM , Zeru T , Tadesse Z , Chernet A , Thompson IJB , Nash SD , Lietman TM , Martin DL , Keenan JD , Arnold BF . J Infect Dis 2023 Monitoring trachoma transmission with antibody data requires characterization of decay in IgG to Chlamydia trachomatis antigens. In a three-year longitudinal cohort in a high transmission setting, we estimated a median IgG half-life of 3 years and a seroreversion rate of 2.5 (95% CI: 1.6, 3.5) per 100 person-years. |
Tropical data: Approach and methodology as applied to trachoma prevalence surveys
Harding-Esch EM , Burgert-Brucker CR , Jimenez C , Bakhtiari A , Willis R , Bejiga MD , Mpyet C , Ngondi J , Boyd S , Abdala M , Abdou A , Adamu Y , Alemayehu A , Alemayehu W , Al-Khatib T , Apadinuwe SC , Awaca N , Awoussi MS , Baayendag G , Badiane MD , Bailey RL , Batcho W , Bay Z , Bella A , Beido N , Bol YY , Bougouma C , Brady CJ , Bucumi V , Butcher R , Cakacaka R , Cama A , Camara M , Cassama E , Chaora SG , Chebbi AC , Chisambi AB , Chu B , Conteh A , Coulibaly SM , Courtright P , Dalmar A , Dat TM , Davids T , Djaker MEA , de Fátima Costa Lopes M , Dézoumbé D , Dodson S , Downs P , Eckman S , Elshafie BE , Elmezoghi M , Elvis AA , Emerson P , Epée EE , Faktaufon D , Fall M , Fassinou A , Fleming F , Flueckiger R , Gamael KK , Garae M , Garap J , Gass K , Gebru G , Gichangi MM , Giorgi E , Goépogui A , Gómez DVF , Gómez Forero DP , Gower EW , Harte A , Henry R , Honorio-Morales HA , Ilako DR , Issifou AAB , Jones E , Kabona G , Kabore M , Kadri B , Kalua K , Kanyi SK , Kebede S , Kebede F , Keenan JD , Kello AB , Khan AA , Khelifi H , Kilangalanga J , Kim SH , Ko R , Lewallen S , Lietman T , Logora MSY , Lopez YA , MacArthur C , Macleod C , Makangila F , Mariko B , Martin DL , Masika M , Massae P , Massangaie M , Matendechero HS , Mathewos T , McCullagh S , Meite A , Mendes EP , Abdi HM , Miller H , Minnih A , Mishra SK , Molefi T , Mosher A , M'Po N , Mugume F , Mukwiza R , Mwale C , Mwatha S , Mwingira U , Nash SD , Nassa C , Negussu N , Nieba C , Noah Noah JC , Nwosu CO , Olobio N , Opon R , Pavluck A , Phiri I , Rainima-Qaniuci M , Renneker KK , Saboyá-Díaz MI , Sakho F , Sanha S , Sarah V , Sarr B , Szwarcwald CL , Shah Salam A , Sharma S , Seife F , Serrano Chavez GM , Sissoko M , Sitoe HM , Sokana O , Tadesse F , Taleo F , Talero SL , Tarfani Y , Tefera A , Tekeraoi R , Tesfazion A , Traina A , Traoré L , Trujillo-Trujillo J , Tukahebwa EM , Vashist P , Wanyama EB , Warusavithana SDP , Watitu TK , West S , Win Y , Woods G , Yajima A , Yaya G , Zecarias A , Zewengiel S , Zoumanigui A , Hooper PJ , Millar T , Rotondo L , Solomon AW . Ophthalmic Epidemiol 2023 30 (6) 544-560 PURPOSE: Population-based prevalence surveys are essential for decision-making on interventions to achieve trachoma elimination as a public health problem. This paper outlines the methodologies of Tropical Data, which supports work to undertake those surveys. METHODS: Tropical Data is a consortium of partners that supports health ministries worldwide to conduct globally standardised prevalence surveys that conform to World Health Organization recommendations. Founding principles are health ministry ownership, partnership and collaboration, and quality assurance and quality control at every step of the survey process. Support covers survey planning, survey design, training, electronic data collection and fieldwork, and data management, analysis and dissemination. Methods are adapted to meet local context and needs. Customisations, operational research and integration of other diseases into routine trachoma surveys have also been supported. RESULTS: Between 29(th) February 2016 and 24(th) April 2023, 3373 trachoma surveys across 50 countries have been supported, resulting in 10,818,502 people being examined for trachoma. CONCLUSION: This health ministry-led, standardised approach, with support from the start to the end of the survey process, has helped all trachoma elimination stakeholders to know where interventions are needed, where interventions can be stopped, and when elimination as a public health problem has been achieved. Flexibility to meet specific country contexts, adaptation to changes in global guidance and adjustments in response to user feedback have facilitated innovation in evidence-based methodologies, and supported health ministries to strive for global disease control targets. |
High prevalence of trachomatous inflammation-follicular with no trachomatous trichiasis: can alternative indicators explain the epidemiology of trachoma in Côte d'Ivoire?
Atekem K , Harding-Esch EM , Martin DL , Downs P , Palmer SL , Kaboré A , Kelly M , Bovary A , Sarr A , Nguessan K , James F , Gwyn S , Wickens K , Bakhtiari A , Boyd S , Aba A , Senyonjo L , Courtright P , Meite A . Int Health 2023 15 ii3-ii11 Baseline trachoma surveys in Côte d'Ivoire (2019) identified seven evaluation units (EUs) with a trachomatous inflammation-follicular (TF) prevalence ≥10%, but a trachomatous trichiasis (TT) prevalence in individuals ≥15 y of age below the elimination threshold (0.2%). Two of these EUs, Bondoukou 1 and Bangolo 2, were selected for a follow-up survey to understand the epidemiology of trachoma using additional indicators of Chlamydia trachomatis infection (DNA from conjunctival swabs) and exposure (anti-Pgp3 and Ct694 antibodies from dried blood spots [DBSs]). A two-stage cluster sampling methodology was used to select villages and households. All individuals 1-9 y of age from each selected household were recruited, graded for trachoma and had a conjunctival swab and DBS collected. Conjunctival swabs and DBSs were tested using Cepheid GeneXpert and a multiplex bead assay, respectively. The age-adjusted TF and infection prevalence in 1- to 9-year-olds was <1% and <0.3% in both EUs. Age-adjusted seroprevalence was 5.3% (95% confidence interval [CI] 1.5 to 15.6) in Bondoukou 1 and 8.2% (95% CI 4.3 to 13.7) in Bangolo 2. The seroconversion rate for Pgp3 was low, at 1.23 seroconversions/100 children/year (95% CI 0.78 to 1.75) in Bondoukou 1 and 1.91 (95% CI 1.58 to 2.24) in Bangolo 2. Similar results were seen for CT694. These infection, antibody and clinical data provide strong evidence that trachoma is not a public health problem in either EU. |
Schistosomiasis seroprevalence among children aged 0-14 years in Nigeria, 2018
Straily A , Tamunonengiyeofori I , Wiegand RE , Iriemenam NC , Okoye MI , Dawurung AB , Ugboaja NB , Tongha M , Parameswaran N , Greby SM , Alagi M , Akpan NM , Nwachukwu WE , Mba N , Martin DL , Secor WE , Swaminathan M , Adetifa I , Ihekweazu C . Am J Trop Med Hyg 2023 110 (1) 90-97 The first nationally representative, population-based study of schistosomiasis seroprevalence in Nigeria was conducted using blood samples and risk-factor data collected during the 2018 Nigeria HIV/AIDS Indicator and Impact Survey (NAIIS). Schistosomiasis seroprevalence was estimated by analyzing samples for reactivity to schistosome soluble egg antigen (SEA) in a multiplex bead assay; NAIIS survey data were assessed to identify potential risk factors for seropositivity. The SEA antibody data were available for 31,459 children aged 0 to 14 years. Overall seroprevalence was 17.2% (95% CI: 16.3-18.1%). Seropositive children were identified in every age group, including children < 5 years, and seroprevalence increased with increasing age (P < 0.0001). Several factors were associated with increased odds of seropositivity, including being a boy (odds ratio [OR] = 1.34, 95% CI: 1.24-1.45), living in a rural area (OR = 2.2, 95% CI: 1.9-2.5), and animal ownership (OR = 1.67, 95% CI: 1.52-1.85). Access to improved sanitation and drinking water sources were associated with decreased odds of seropositivity (OR = 0.52, 95% CI: 0.47-0.58 and OR = 0.53, 95% CI: 0.47-0.60, respectively) regardless of whether the child lived in a rural (sanitation: adjusted odds ratio [aOR] = 0.7, 95% CI: 0.6-0.8; drinking water: aOR = 0.7, 95% CI: 0.6-0.8) or urban area (sanitation: aOR = 0.6, 95% CI: 0.5-0.7; drinking water: aOR = 0.5, 95% CI: 0.4-0.6), highlighting the importance of these factors for schistosomiasis prevention and control. These results identified additional risk populations (children < 5 years) and a new risk factor (animal ownership) and could be used to monitor the impact of control programs. |
Age-specific prevalence of anti-Pgp3 antibodies and severe conjunctival scarring in the Solomon Islands (preprint)
Butcher R , Sokana O , Jack K , Martin DL , Burton MJ , Solomon AW , Mabey DCW , Roberts CH . bioRxiv 2017 141135 Background Trachomatous trichiasis (TT) and ocular Chlamydia trachomatis (Ct) infection in the Solomon Islands are scarce, whereas trachomatous inflammation–follicular (TF) is prevalent.Methods We enrolled 1511 people aged ≥1 year from randomly selected households in 13 villages in which >10% of the population had TF prior to a single round of azithromycin MDA undertaken six months previously. Blood was collected from people of all ages to be screened for anti-Pgp3 antibodies. Photographs were collected from people of all ages for analysis of scarring severity.Results Conjunctival scars were visible in 13.1% of photographs. Mild (p<0.0001) but not severe (p=0.149) scars increased in prevalence with age. Anti-Pgp3 antibody seroprevalence was 18% in 1–9 year olds, increased sharply around the age of sexual debut, and reached 69% in those over 25 years. Anti-Pgp3 seropositivity did not increase significantly between the ages of 1–9 years, and was not associated with scarring in children (p=0.472) or TF in children (p=0.581).Conclusions Signs of trachoma are common in the Solomon Islands but occur frequently in individuals who have no serological evidence of prior ocular infection with Ct. WHO recommendations for directing MDA provision based on signs alone may not be suitable in this context. |
Predicting future ocular Chlamydia trachomatis infection prevalence using serological, clinical, molecular, and geospatial data (preprint)
Tedijanto C , Aragie S , Tadesse Z , Haile M , Zeru T , Nash SD , Wittberg DM , Gwyn S , Martin DL , Sturrock HJW , Lietman TM , Keenan JD , Arnold BF . medRxiv 2021 2021.07.19.21260623 Trachoma is an infectious disease characterized by repeated exposures to Chlamydia trachomatis (Ct) that may ultimately lead to blindness. Certain areas, particularly in Africa, pose persistent challenges to elimination of trachoma as a public health problem. Efficiently identifying communities with high infection burden could help target more intensive control efforts. We hypothesized that IgG seroprevalence in combination with geospatial layers, machine learning, and model-based geostatistics would be able to accurately predict future community-level ocular Ct infections detected by PCR. We used measurements from 40 communities in the hyperendemic Amhara region of Ethiopia. Median Ct infection prevalence among children 0-5 years old increased from 6% at enrollment to 29% by month 36. At baseline, correlation between seroprevalence and Ct infection was stronger among children 0-5 years old (ρ = 0.77) than children 6-9 years old (ρ = 0.48), and stronger than the correlation between clinical trachoma and Ct infection (0-5y ρ = 0.56; 6-9y ρ = 0.40). Seroprevalence was the strongest concurrent predictor of infection prevalence at month 36 among children 0-5 years old (cross-validated R2 = 0.75, 95% CI: 0.58-0.85), though predictive performance declined substantially with increasing temporal lag between predictor and outcome measurements. Geospatial variables, a spatial Gaussian process, and stacked ensemble machine learning did not meaningfully improve predictions. Serological markers among children 0-5 years old may be an objective, programmatic tool for identifying communities with high levels of active ocular Ct infections, but accurate, future prediction in the context of changing transmission remains an open challenge.SIGNIFICANCE STATEMENT Trachoma is targeted for elimination as a public health problem by 2030. District-level estimates of clinical disease among children 1-9 years old are currently used to guide control programs and assess elimination. However, clinical trachoma is a subjective indicator. Serological markers present an objective, scalable alternative that could be measured in integrated platforms. In a hyperendemic region, community-level seroprevalence aligned more closely with concurrent infection prevalence than clinical trachoma. The correlation between seroprevalence and infection prevalence was stronger among 0–5-year-olds compared to 6–9-year-olds and was consistent over a three-year period of increasing transmission. Serosurveillance among children 0-5 years old may be a promising monitoring strategy to identify communities with the highest burdens of ocular chlamydial infection.Competing Interest StatementThe authors have declared no competing interest.Clinical TrialNCT02754583Funding StatementWe would like to thank the WUHA study participants and field team without whom this research would not be possible. This work was supported by the National Institute of Allergy and Infectious Diseases (R03 AI147128 to BFA) and the National Eye Institute (U10 EY023939 to JDK). This work was also made possible in part by an Unrestricted Grant from Research to Prevent Blindness. We would also like to thank Abbott for its donation of the m2000 RealTime molecular diagnostics system and consumables.Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:Approval for the study was obtained from the University of California, San Francisco Institutional Review Board (14-14004).All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).YesI have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.YesDe-identified data and code to replicate this work is available on Github. https://github.com/ctedijanto/swift-spatial-prediction |
Effect of biannual azithromycin distribution on antibody responses to malaria, bacterial, and protozoan pathogens among children: A cluster-randomized, placebo-controlled trial in Niger (preprint)
Arzika AM , Maliki R , Goodhew EB , Rogier E , Priest JW , Lebas E , O'Brien KS , Le V , Oldenburg CE , Doan T , Porco TC , Keenan JD , Lietman TM , Martin DL , Arnold BF . medRxiv 2021 2021.04.23.21255957 Background The Macrolides Oraux pour Réduire les Décès avec un Oeil sur la Résistance (MORDOR) trial in Niger, Malawi, and Tanzania found that biannual mass distribution of azithromycin to children younger than 5 years led to a 13.5% reduction in all-cause mortality. Additional endpoints in the trial have attempted to elucidate the mechanisms for mortality reduction. In this pre-specified secondary analysis, we assessed the effect of azithromycin compared with placebo on IgG- based measures of infectious disease exposure with a multiplex bead assay that included antigens to malaria parasites (Plasmodium falciparum, P. vivax, P. malariae, P. ovale), bacterial pathogens (Campylobacter spp., enterotoxigenic Escherichia coli, Vibrio cholerae, Salmonella enterica, Streptococcus pyogenes) and protozoans (Cryptosporidium parvum, Giardia duodenales).Methods and Findings Thirty communities in rural Niger were randomized 1:1 to biannual distributions of azithromycin or placebo among children ages 1-59 months. The analysis included 5,642 blood specimens collected from 3,814 children ages 1-59 months, measured at 6, 12, 24, and 36 months of follow-up in a repeated cross-sectional design. Campylobacter spp. seroprevalence averaged over all study visits was lower in azithromycin communities compared to placebo (91% vs 94%, difference = –3%, 95% CI: –5%, –1%; P=0.03), which corresponded to a 29% lower seroconversion rate (1.30 versus 1.84 seroconversions per year, hazard ratio = 0.71, 95% CI: 0.56, 0.89; P=0.004). Antibody-based measures of infection with P. falciparum and group A streptococcus were consistently lower in azithromycin communities, but were not statistically different from placebo, and there were no other differences across pathogens. Strengths of the study included masking of participants, investigators, and analysts, high treatment coverage, large sample size, and objective outcomes. Principal limitations included the timing of blood collection with respect to treatment (approximately 6 months later, which could have missed transient effects in the weeks immediately following treatment), and the durability of IgG response following clearance of infection. Both limitations would lead the trial to under-estimate effects on antibody-based measures of infection.Conclusions The reduction in Campylobacter spp. despite these limitations suggests an effect on carriage, findings which align with an independent metagenomic analysis of rectal swabs collected in the same villages and with previously reported reductions in dysentery-associated mortality. Given significant sequelae of Campylobacter infection among preschool aged children, our results support at least one possible mechanism through which biannual mass distribution of azithromycin likely reduced mortality in this study population.Competing Interest StatementThis work was supported by the Bill & Melinda Gates Foundation (award no. OPP1032340 to TML) and was supported in part by an unrestricted grant from Research to Prevent Blindness and by the National Institute of Allergy and Infectious Diseases (award no. K01-AI119180 to BFA). The Gates Foundation approved the study design, but had no role in data collection, data analysis, data interpretation, or writing of the report. The authors declare no competing interests. The findings and conclusions in this article are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. Use of trade names is for identification only and does not imply endorsement by the Public Health Service or by the U.S. Department of Health and Human Services. Clinical TrialNCT02048007Funding StatementThis work was supported by the Bill & Melinda Gates Foundation (award no. OPP1032340 to TML) and was supported in part by an unrestricted grant from Research to Prevent Blindness and by the National Institute of Allergy and Infectious Diseases (award no. K01-AI119180 to BFA). The Gates Foundation approved the study design, but had no role in data collection, data nalysis, data interpretation, or writing of the report.Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:The trial protocol was reviewed and approved by the Committee on Human Research at the University of California, San Francisco, and the Niger Ministry of Health's Ethical Committee. Parents or guardians of enrolled children provided oral consent before each azithromycin or placebo treatment and at each specimen collection visit. Parents or guardians were instructed to report any adverse event within 7 days of treatment by contacting their village representative, who then reported events to the site coordinator and UCSF. An independent Data and Safety Monitoring Committee provided additional oversight. CDC researchers had access to de-identified samples for analysis (no personally identifying information).All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.YesData and computational notebooks used to conduct the analyses are available through the Open Science Framework (https://osf.io/954bt) and Dryad (xx DOI forthcoming xx). Analyses used R statistical software, version 4.0.2. https://osf.io/954bt |
Enteropathogen antibody dynamics and force of infection among children in low-resource settings (preprint)
Arnold BF , Martin DL , Juma J , Mkocha H , Ochieng JB , Cooley GM , Omore R , Goodhew EB , Morris JF , Costantini V , Vinje J , Lammie PJ , Priest JW . bioRxiv 2019 522920 Little is known about enteropathogen seroepidemiology among children in low-resource settings. We measured serological IgG responses to eight enteropathogens (Giardia intestinalis, Cryptosporidium parvum, Entamoeba histolytica, Salmonella enterica, enterotoxigenic Escherichia coli, Vibrio cholerae, Campylobacter jejuni, norovirus) in cohorts from Haiti, Kenya, and Tanzania. We studied antibody dynamics and force of infection across pathogens and cohorts. Enteropathogens shared common seroepidemiologic features that enabled between-pathogen comparisons of transmission. Overall, exposure was intense: for most pathogens the window of primary infection was <3 years old; for highest transmission pathogens primary infection occurred within the first year. Longitudinal profiles revealed significant IgG boosting and waning above seropositivity cutoffs, underscoring the value of longitudinal designs to estimate force of infection. Seroprevalence and force of infection were rank-preserving across pathogens, illustrating the measures provide similar information about transmission heterogeneity. Our findings suggest multiplex antibody assays are a promising approach to measure population-level enteropathogen transmission in serologic surveillance. |
Seroreversion to Chlamydia trachomatis Pgp3 antigen among young children in a hyperendemic region of Amhara, Ethiopia (preprint)
Tedijanto C , Aragie S , Gwyn S , Wittberg DM , Zeru T , Tadesse Z , Chernet A , Thompson I , Nash SD , Lietman TM , Martin DL , Keenan JD , Arnold BF . medRxiv 2023 07 Monitoring trachoma transmission with antibody data requires characterization of decay in IgG to Chlamydia trachomatis antigens. In a three-year longitudinal cohort in a high transmission setting, we estimated a median IgG half-life of 3 years and a seroreversion rate of 2.5 (95% CI: 1.6, 3.8) per 100 person-years. Copyright The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. This article is a US Government work. It is not subject to copyright under 17 USC 105 and is also made available for use under a CC0 license. |
Monitoring transmission intensity of trachoma with serology: a multi-country study (preprint)
Tedijanto C , Solomon AW , Martin DL , Nash SD , Keenan JD , Lietman TM , Lammie PJ , Aiemjoy K , Amza A , Aragie S , Arzika AM , Callahan EK , Carolan S , Dawed AA , Goodhew EB , Gwyn S , Hammou J , Kadri B , Kalua K , Maliki R , Nassirou B , Seife F , Tadesse Z , West SK , Wittberg DM , Zeru T , Arnold BF . medRxiv 2023 16 Trachoma, caused by ocular Chlamydia trachomatis infection, is targeted for global elimination as a public health problem by 2030. To provide evidence for use of antibodies to monitor C. trachomatis transmission, we collated IgG responses to Pgp3 antigen, PCR positivity, and clinical observations from 19,811 children aged 1-9 years in 14 populations. We demonstrate that age-seroprevalence curves consistently shift along a gradient of transmission intensity: rising steeply in populations with high levels of infection and active trachoma and becoming flat in populations near elimination. Seroprevalence (range: 0-54%) and seroconversion rates (range: 0-15 per 100 person-years) correlate with PCR prevalence (r: 0.88, 95% CI: 0.77, 0.93). A seroprevalence threshold of 13.5% (seroconversion rate 2.75 per 100 person-years) identifies clusters with any infection at high sensitivity (>90%) and moderate specificity (69-75%). Antibody responses in young children provide a robust, generalizable approach to monitor population progress toward and beyond trachoma elimination. Copyright The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. This article is a US Government work. It is not subject to copyright under 17 USC 105 and is also made available for use under a CC0 license. |
Changes in trachoma indicators in Kiribati with two rounds of azithromycin mass drug administration, measured in serial population-based surveys
Goodhew EB , Taoaba R , Harding-Esch EM , Gwyn SE , Bakhtiari A , Butcher R , Cama A , Guagliardo SAJ , Jimenez C , Mpyet CD , Tun K , Wickens K , Solomon AW , Martin DL , Tekeraoi R . PLoS Negl Trop Dis 2023 17 (7) e0011441 Baseline mapping in the two major population centers of Kiribati showed that trachoma was a public health problem in need of programmatic interventions. After conducting two annual rounds of antibiotic mass drug administration (MDA), Kiribati undertook trachoma impact surveys in 2019, using standardized two-stage cluster surveys in the evaluation units of Kiritimati Island and Tarawa. In Kiritimati, 516 households were visited and in Tarawa, 772 households were visited. Nearly all households had a drinking water source and access to an improved latrine. The prevalence of trachomatous trichiasis remained above the elimination threshold (0.2% in ≥15-year-olds) and was virtually unchanged from baseline. The prevalence of trachomatous inflammation-follicular (TF) in 1-9-year-olds decreased by approximately 40% from baseline in both evaluation units but remained above the 5% TF prevalence threshold for stopping MDA. TF prevalence at impact survey was 11.5% in Kiritimati and 17.9% in Tarawa. Infection prevalence in 1-9-year-olds by PCR was 0.96% in Kiritimati and 3.3% in Tarawa. Using a multiplex bead assay to measure antibodies to the C. trachomatis antigen Pgp3, seroprevalence in 1-9-year-olds was 30.2% in Kiritimati and 31.4% in Tarawa. The seroconversion rate, in seroconversion events/100 children/year, was 9.0 in Kiritimati and 9.2 in Tarawa. Seroprevalence and seroconversion rates were both assessed by four different assays, with strong agreement between tests. These results show that, despite decreases in indicators associated with infection at impact survey, trachoma remains a public health problem in Kiribati, and provide additional information about changes in serological indicators after MDA. |
Monitoring transmission intensity of trachoma with serology
Tedijanto C , Solomon AW , Martin DL , Nash SD , Keenan JD , Lietman TM , Lammie PJ , Aiemjoy K , Amza A , Aragie S , Arzika AM , Callahan EK , Carolan S , Dawed AA , Goodhew EB , Gwyn S , Hammou J , Kadri B , Kalua K , Maliki R , Nassirou B , Seife F , Tadesse Z , West SK , Wittberg DM , Zeru Tadege T , Arnold BF . Nat Commun 2023 14 (1) 3269 Trachoma, caused by ocular Chlamydia trachomatis infection, is targeted for global elimination as a public health problem by 2030. To provide evidence for use of antibodies to monitor C. trachomatis transmission, we collated IgG responses to Pgp3 antigen, PCR positivity, and clinical observations from 19,811 children aged 1-9 years in 14 populations. We demonstrate that age-seroprevalence curves consistently shift along a gradient of transmission intensity: rising steeply in populations with high levels of infection and active trachoma and becoming flat in populations near elimination. Seroprevalence (range: 0-54%) and seroconversion rates (range: 0-15 per 100 person-years) correlate with PCR prevalence (r: 0.87, 95% CI: 0.57, 0.97). A seroprevalence threshold of 13.5% (seroconversion rate 2.75 per 100 person-years) identifies clusters with any PCR-identified infection at high sensitivity ( >90%) and moderate specificity (69-75%). Antibody responses in young children provide a robust, generalizable approach to monitor population progress toward and beyond trachoma elimination. |
Lessons learned from the implementation of integrated serosurveillance of communicable diseases in the Americas
Saboyá-Díaz MI , Castellanos LG , Morice A , Ade MP , Rey-Benito G , Cooley GM , Scobie HM , Wiegand RE , Coughlin MM , Martin DL . Rev Panam Salud Publica 2023 47 e53 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. |
Comparison of one single-antigen assay and three multi-antigen SARS-CoV-2 IgG assays in Nigeria
Iriemenam NC , Ige FA , Greby SM , Okunoye OO , Uwandu M , Aniedobe M , Nwaiwu SO , Mba N , Okoli M , William NE , Ehoche A , Mpamugo A , Mitchell A , Stafford KA , Thomas AN , Olaleye T , Akinmulero OO , Agala NP , Abubakar AG , Owens A , Gwyn SE , Rogier E , Udhayakumar V , Steinhardt LC , Martin DL , Okoye MI , Audu R . J Clin Virol Plus 2023 3 (1) 100139 OBJECTIVES: Determining an accurate estimate of SARS-CoV-2 seroprevalence has been challenging in African countries where malaria and other pathogens are endemic. We compared the performance of one single-antigen assay and three multi-antigen SARS-CoV-2 IgG assays in a Nigerian population endemic for malaria. METHODS: De-identified plasma specimens from SARS-CoV-2 RT-PCR positive, dried blood spot (DBS) SARS-CoV-2 RT-PCR positive, and pre-pandemic negatives were used to evaluate the performance of the four SARS-CoV-2 assays (Tetracore, SARS2MBA, RightSign, xMAP). RESULTS: Results showed higher sensitivity with the multi-antigen (81% (Tetracore), 96% (SARS2MBA), 85% (xMAP)) versus the single-antigen (RightSign (64%)) SARS-CoV-2 assay. The overall specificities were 98% (Tetracore), 100% (SARS2MBA and RightSign), and 99% (xMAP). When stratified based on <15 days to ≥15 days post-RT-PCR confirmation, the sensitivities increased from 75% to 88.2% for Tetracore; from 93% to 100% for the SARS2MBA; from 58% to 73% for RightSign; and from 83% to 88% for xMAP. With DBS, there was no positive increase after 15-28 days for the three assays (Tetracore, SARS2MBA, and xMAP). CONCLUSION: Multi-antigen assays performed well in Nigeria, even with samples with known malaria reactivity, and might provide more accurate measures of COVID-19 seroprevalence and vaccine efficacy. |
Diagnostics to support the eradication of yaws-Development of two target product profiles.
Fongwen N , Handley BL , Martin DL , Beiras C , Dyson L , Frimpong M , Mitja O , Asiedu K , Marks M . PLoS Negl Trop Dis 2022 16 (9) e0010554 BACKGROUND: Yaws is targeted for eradication by 2030, using a strategy based on mass drug administration (MDA) with azithromycin. New diagnostics are needed to aid eradication. Serology is currently the mainstay for yaws diagnosis; however, inaccuracies associated with current serological tests makes it difficult to fully assess the need for and impact of eradication campaigns using these tools. Under the recommendation of the WHO Diagnostic Technical Advisory Group (DTAG) for Neglected Tropical Diseases(NTDs), a working group was assembled and tasked with agreeing on priority use cases for developing target product profiles (TPPs) for new diagnostics tools. METHODOLOGY AND PRINCIPAL FINDINGS: The working group convened three times and established two use cases: identifying a single case of yaws and detecting azithromycin resistance. One subgroup assessed the current diagnostic landscape for yaws and a second subgroup determined the test requirements for both use cases. Draft TPPs were sent out for input from stakeholders and experts. Both TPPs considered the following parameters: product use, design, performance, configuration, cost, access and equity. To identify a single case of yaws, the test should be able to detect an analyte which confirms an active infection with at least 95% sensitivity and 99.9% specificity. The high specificity was deemed important to avoid a high false positive rate which could result in unnecessary continuation or initiation of MDA campaigns. If used in settings where the number of suspected cases is low, further testing could be considered to compensate for imperfect sensitivity and to improve specificity. The test to detect azithromycin resistance should be able to detect known genetic resistance mutations with a minimum sensitivity and specificity of 95%, with the caveat that all patients with suspected treatment failure should be treated as having resistant yaws and offered alternative treatment. CONCLUSIONS: The TPPs developed will provide test developers with guidance to ensure that novel diagnostic tests meet identified public health needs. |
Effect of biannual mass azithromycin distributions to preschool-aged children on trachoma prevalence in Niger: A cluster randomized clinical trial
Arzika AM , Mindo-Panusis D , Abdou A , Kadri B , Nassirou B , Maliki R , Alsoudi AF , Zhang T , Cotter SY , Lebas E , O'Brien KS , Callahan EK , Bailey RL , West SK , Goodhew EB , Martin DL , Arnold BF , Porco TC , Lietman TM , Keenan JD . JAMA Netw Open 2022 5 (8) e2228244 IMPORTANCE: Because transmission of ocular strains of Chlamydia trachomatis is greatest among preschool-aged children, limiting azithromycin distributions to this age group may conserve resources and result in less antimicrobial resistance, which is a potential advantage in areas with hypoendemic trachoma and limited resources. OBJECTIVE: To determine the efficacy of mass azithromycin distributions to preschool-aged children as a strategy for trachoma elimination in areas with hypoendemic disease. DESIGN, SETTING, AND PARTICIPANTS: In this cluster randomized clinical trial performed from November 23, 2014, until July 31, 2017, thirty rural communities in Niger were randomized at a 1:1 ratio to biannual mass distributions of either azithromycin or placebo to children aged 1 to 59 months. Participants and study personnel were masked to treatment allocation. Data analyses for trachoma outcomes were performed from October 19, 2021, through June 10, 2022. INTERVENTIONS: Every 6 months, a single dose of either oral azithromycin (20 mg/kg using height-based approximation for children who could stand or weight calculation for small children) or oral placebo was provided to all children aged 1 to 59 months. MAIN OUTCOMES AND MEASURES: Trachoma was a prespecified outcome of the trial, assessed as the community-level prevalence of trachomatous inflammation-follicular and trachomatous inflammation-intense through masked grading of conjunctival photographs from a random sample of 40 children per community each year during the 2-year study period. A secondary outcome was the seroprevalence of antibodies to C trachomatis antigens. RESULTS: At baseline, 4726 children in 30 communities were included; 1695 children were enrolled in 15 azithromycin communities and 3031 children were enrolled in 15 placebo communities (mean [SD] proportions of boys, 51.8% [4.7%] vs 52.0% [4.2%]; mean [SD] age, 30.8 [2.8] vs 30.6 [2.6] months). The mean coverage of study drug for the 4 treatments was 79% (95% CI, 75%-83%) in the azithromycin group and 82% (95% CI, 79%-85%) in the placebo group. The mean prevalence of trachomatous inflammation-follicular at baseline was 1.9% (95% CI, 0.5%-3.5%) in the azithromycin group and 0.9% (95% CI, 0-1.9%) in the placebo group. At 24 months, trachomatous inflammation-follicular prevalence was 0.2% (95% CI, 0-0.5%) in the azithromycin group and 0.8% (95% CI, 0.2%-1.6%) in the placebo group (incidence rate ratio adjusted for baseline: 0.18 [95% CI, 0.01-1.20]; permutation P = .07). CONCLUSIONS AND RELEVANCE: The findings of this trial do not show that biannual mass azithromycin distributions to preschool-aged children were more effective than placebo, although the underlying prevalence of trachoma was low. The sustained absence of trachoma even in the placebo group suggests that trachoma may have been eliminated as a public health problem in this part of Niger. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02048007. |
Performance of SARS-CoV-2 Antigens in a Multiplex Bead Assay for Integrated Serological Surveillance of Neglected Tropical and Other Diseases.
Gwyn S , Abubakar A , Akinmulero O , Bergeron E , Blessing UN , Chaitram J , Coughlin MM , Dawurung AB , Dickson FN , Esiekpe M , Evbuomwan E , Greby SM , Iriemenam NC , Kainulainen MH , Naanpoen TA , Napoloen L , Odoh I , Okoye M , Olaleye T , Schuh AJ , Owen SM , Samuel A , Martin DL . Am J Trop Med Hyg 2022 107 (2) 260-7 Serosurveillance can provide estimates of population-level exposure to infectious pathogens and has been used extensively during the COVID-19 pandemic. Simultaneous, serological testing for multiple pathogens can be done using bead-based immunoassays to add value to disease-specific serosurveys. We conducted a validation of four SARS-CoV-2 antigens-full-length spike protein, two receptor binding domain proteins, and the nucleocapsid protein-on our existing multiplex bead assay (MBA) for enteric diseases, malaria, and vaccine preventable diseases. After determining the optimal conditions for coupling the antigens to microsphere beads, the sensitivity and specificity of the assay were determined on two instruments (Luminex-200 and MAGPIX) when testing singly (monoplex) versus combined (multiplex). Sensitivity was assessed using plasma from 87 real-time reverse transcription polymerase chain reaction (rRT-PCR) positive persons collected in March-May of 2020 and ranged from 94.3% to 96.6% for the different testing conditions. Specificity was assessed using 98 plasma specimens collected prior to December 2019 and plasma from 19 rRT-PCR negative persons and ranged from 97.4% to 100%. The positive percent agreement was 93.8% to 97.9% using 48 specimens collected > 21 days post-symptom onset, while the negative percent agreement was ≥ 99% for all antigens. Test performance was similar using monoplex or multiplex testing. Integrating SARS-CoV-2 serology with other diseases of public health interest could add significant value to public health programs that have suffered severe programmatic setbacks during the COVID-19 pandemic. |
Predicting future community-level ocular Chlamydia trachomatis infection prevalence using serological, clinical, molecular, and geospatial data
Tedijanto C , Aragie S , Tadesse Z , Haile M , Zeru T , Nash SD , Wittberg DM , Gwyn S , Martin DL , Sturrock HJW , Lietman TM , Keenan JD , Arnold BF . PLoS Negl Trop Dis 2022 16 (3) e0010273 Trachoma is an infectious disease characterized by repeated exposures to Chlamydia trachomatis (Ct) that may ultimately lead to blindness. Efficient identification of communities with high infection burden could help target more intensive control efforts. We hypothesized that IgG seroprevalence in combination with geospatial layers, machine learning, and model-based geostatistics would be able to accurately predict future community-level ocular Ct infections detected by PCR. We used measurements from 40 communities in the hyperendemic Amhara region of Ethiopia to assess this hypothesis. Median Ct infection prevalence among children 0-5 years old increased from 6% at enrollment, in the context of recent mass drug administration (MDA), to 29% by month 36, following three years without MDA. At baseline, correlation between seroprevalence and Ct infection was stronger among children 0-5 years old (ρ = 0.77) than children 6-9 years old (ρ = 0.48), and stronger than the correlation between active trachoma and Ct infection (0-5y ρ = 0.56; 6-9y ρ = 0.40). Seroprevalence was the strongest concurrent predictor of infection prevalence at month 36 among children 0-5 years old (cross-validated R2 = 0.75, 95% CI: 0.58-0.85), though predictive performance declined substantially with increasing temporal lag between predictor and outcome measurements. Geospatial variables, a spatial Gaussian process, and stacked ensemble machine learning did not meaningfully improve predictions. Serological markers among children 0-5 years old may be an objective tool for identifying communities with high levels of ocular Ct infections, but accurate, future prediction in the context of changing transmission remains an open challenge. |
Post-validation survey in two districts of Morocco after the elimination of trachoma as a public health problem
Hammou J , Guagliardo SAJ , Obtel M , Razine R , Haroun AE , Youbi M , Bellefquih AM , White M , Gwyn S , Martin DL . Am J Trop Med Hyg 2022 106 (5) 1370-8 Trachoma is the leading infectious cause of blindness. In 2016, Morocco was validated by WHO as having eliminated trachoma as a public health problem. We evaluated two previously endemic districts in Morocco for trachomatous inflammation-follicular (TF), trachomatous trichiasis (TT), and antibodies against Chlamydia trachomatis, the causative agent of trachoma. Community-based cross-sectional surveys in the districts of Boumalene Dades and Agdez included 4,445 participants for whom both questionnaire and serology data were available; 58% were aged 1-9 years. Participants had eyes examined for TF and blood collected for analysis of antibodies to the C. trachomatis antigen Pgp3 by both a multiplex bead assay (MBA) and lateral flow assay (LFA). Seroconversion rates (SCR) per 100 people per year were used to estimate changes in the force of infection using Bayesian serocatalytic models. In Agdez, TF prevalence in 1-9-year-olds was 0.3%, seroprevalence ranged from 9.4% to 11.4%, and SCR estimates ranged from 2.4 to 3.0. In Boumalene Dades, TF prevalence in 1-9-year-olds was 0.07%, and modeling data from the different assays indicated a decrease in transmission between 20 and 24 years ago. The TF data support an absence of active trachoma in the two districts examined. However, seroprevalence and SCR in younger people were higher in Agdez than Boumalene Dades, showing that there can be differences in serology metrics in areas with similar TF prevalence. Data will be included in multicountry analyses to better understand potential thresholds for serological surveillance in trachoma. |
Characterising spatial patterns of neglected tropical disease transmission using integrated sero-surveillance in Northern Ghana
Fornace KM , Senyonjo L , Martin DL , Gwyn S , Schmidt E , Agyemang D , Marfo B , Addy J , Mensah E , Solomon AW , Bailey R , Drakeley CJ , Pullan RL . PLoS Negl Trop Dis 2022 16 (3) e0010227 BACKGROUND: As prevalence decreases in pre-elimination settings, identifying the spatial distribution of remaining infections to target control measures becomes increasingly challenging. By measuring multiple antibody responses indicative of past exposure to different pathogens, integrated serological surveys enable simultaneous characterisation of residual transmission of multiple pathogens. METHODOLOGY/PRINCIPAL FINDINGS: Here, we combine integrated serological surveys with geostatistical modelling and remote sensing-derived environmental data to estimate the spatial distribution of exposure to multiple diseases in children in Northern Ghana. The study utilised the trachoma surveillance survey platform (cross-sectional two-stage cluster-sampled surveys) to collect information on additional identified diseases at different stages of elimination with minimal additional cost. Geostatistical modelling of serological data allowed identification of areas with high probabilities of recent exposure to diseases of interest, including areas previously unknown to control programmes. We additionally demonstrate how serological surveys can be used to identify areas with exposure to multiple diseases and to prioritise areas with high uncertainty for future surveys. Modelled estimates of cluster-level prevalence were strongly correlated with more operationally feasible metrics of antibody responses. CONCLUSIONS/SIGNIFICANCE: This study demonstrates the potential of integrated serological surveillance to characterise spatial distributions of exposure to multiple pathogens in low transmission and elimination settings when the probability of detecting infections is low. |
Effect of biannual azithromycin distribution on antibody responses to malaria, bacterial, and protozoan pathogens in Niger
Arzika AM , Maliki R , Goodhew EB , Rogier E , Priest JW , Lebas E , O'Brien KS , Le V , Oldenburg CE , Doan T , Porco TC , Keenan JD , Lietman TM , Martin DL , Arnold BF . Nat Commun 2022 13 (1) 976 The MORDOR trial in Niger, Malawi, and Tanzania found that biannual mass distribution of azithromycin to children younger than 5 years led to a 13.5% reduction in all-cause mortality (NCT02048007). To help elucidate the mechanism for mortality reduction, we report IgG responses to 11 malaria, bacterial, and protozoan pathogens using a multiplex bead assay in pre-specified substudy of 30 communities in the rural Niger placebo-controlled trial over a three-year period (n = 5642 blood specimens, n = 3814 children ages 1-59 months). Mass azithromycin reduces Campylobacter spp. force of infection by 29% (hazard ratio = 0.71, 95% CI: 0.56, 0.89; P = 0.004) but serological measures show no significant differences between groups for other pathogens against a backdrop of high transmission. Results align with a recent microbiome study in the communities. Given significant sequelae of Campylobacter infection among preschool aged children, our results support an important mechanism through which biannual mass distribution of azithromycin likely reduces mortality in Niger. |
Water, sanitation, and hygiene for control of trachoma in Ethiopia (WUHA): a two-arm, parallel-group, cluster-randomised trial
Aragie S , Wittberg DM , Tadesse W , Dagnew A , Hailu D , Chernet A , Melo JS , Aiemjoy K , Haile M , Zeru T , Tadesse Z , Gwyn S , Martin DL , Arnold BF , Freeman MC , Nash SD , Callahan EK , Porco TC , Lietman TM , Keenan JD . Lancet Glob Health 2022 10 (1) e87-e95 BACKGROUND: WHO promotes the SAFE strategy for the elimination of trachoma as a public health programme, which promotes surgery for trichiasis (ie, the S component), antibiotics to clear the ocular strains of chlamydia that cause trachoma (the A component), facial cleanliness to prevent transmission of secretions (the F component), and environmental improvements to provide water for washing and sanitation facilities (the E component). However, little evidence is available from randomised trials to support the efficacy of interventions targeting the F and E components of the strategy. We aimed to determine whether an integrated water, sanitation, and hygiene (WASH) intervention prevents the transmission of trachoma. METHODS: The WASH Upgrades for Health in Amhara (WUHA) was a two-arm, parallel-group, cluster-randomised trial in 40 rural communities in Wag Hemra Zone (Amhara Region, Ethiopia) that had been treated with 7 years of annual mass azithromycin distributions. The randomisation unit was the school catchment area. All households within a 1·5 km radius of a potential water point within the catchment area (as determined by the investigators) were eligible for inclusion. Clusters were randomly assigned (at a 1:1 ratio) to receive a WASH intervention either immediately (intervention) or delayed until the conclusion of the trial (control), in the absence of concurrent antibiotic distributions. Given the nature of the intervention, participants and field workers could not be masked, but laboratory personnel were masked to treatment allocation. The WASH intervention consisted of both hygiene infrastructure improvements (namely, construction of a community water point) and hygiene promotion by government, school, and community leaders, which were implemented at the household, school, and community levels. Hygiene promotion focused on two simple messages: to use soap and water to wash your or your child's face, and to always use a latrine for defecation. The primary outcome was the cluster-level prevalence of ocular chlamydia, measured annually using conjunctival swabs in a random sample of children aged 0-5 years from each cluster at 12, 24, and 36 month timepoints. Analyses were done in an intention-to-treat manner. This trial is ongoing and is registered at ClinicalTrials.gov, NCT02754583. FINDINGS: Between Nov 9, 2015, and March 5, 2019, 40 of 44 clusters assessed for eligibility were enrolled and randomly allocated to the trial groups (20 clusters each, with 7636 people from 1751 households in the intervention group and 9821 people from 2211 households in the control group at baseline). At baseline, ocular chlamydia prevalence among children aged 0-5 years was 11% (95% CI 6 to 16) in the WASH group and 11% (5 to 18) in the control group. At month 36, ocular chlamydia prevalence had increased in both groups, to 32% (24 to 41) in the WASH group and 31% (21 to 41) in the control group (risk difference across three annual monitoring visits, after adjustment for prevalence at baseline: 3·7 percentage points; 95% CI -4·9 to 12·4; p=0·40). No adverse events were reported in either group. INTERPRETATION: An integrated WASH intervention addressing the F and E components of the SAFE strategy did not prevent an increase in prevalence of ocular chlamydia following cessation of antibiotics in an area with hyperendemic trachoma. The impact of WASH in the presence of annual mass azithromycin distributions is currently being studied in a follow-up trial of the 40 study clusters. Continued antibiotic distributions will probably be important in areas with persistent trachoma. FUNDING: National Institutes of Health-National Eye Institute. TRANSLATION: For the Amharic translation of the abstract see Supplementary Materials section. |
Surveillance for peri-elimination trachoma recrudescence: Exploratory studies in Ghana
Senyonjo L , Addy J , Martin DL , Agyemang D , Yeboah-Manu D , Gwyn S , Marfo B , Asante-Poku A , Aboe A , Solomon AW , Bailey RL . PLoS Negl Trop Dis 2021 15 (9) e0009744 INTRODUCTION: To date, eleven countries have been validated as having eliminated trachoma as a public health problem, including Ghana in 2018. Surveillance for recrudescence is needed both pre- and post-validation but evidence-based guidance on appropriate strategies is lacking. We explored two potential surveillance strategies in Ghana. METHODOLOGY/PRINCIPAL FINDINGS: Amongst randomly-selected communities enrolled in pre-validation on-going surveillance between 2011 and 2015, eight were identified as having had trachomatous-inflammation follicular (TF) prevalence ≥5% in children aged 1-9 years between 2012 and 2014. These eight were re-visited in 2015 and 2016 and neighbouring communities were also added ("TF trigger" investigations). Resident children aged 1-9 years were then examined for trachoma and had a conjunctival swab to test for Chlamydia trachomatis (Ct) and a dried blood spot (DBS) taken to test for anti-Pgp3 antibodies. These investigations identified at least one community with evidence of probable recent Ct ocular transmission. However, the approach likely lacks sufficient spatio-temporal power to be reliable. A post-validation surveillance strategy was also evaluated, this reviewed the ocular Ct infection and anti-Pgp3 seroprevalence data from the TF trigger investigations and from the pre-validation surveillance surveys in 2015 and 2016. Three communities identified as having ocular Ct infection >0% and anti-Pgp3 seroprevalence ≥15.0% were identified, and along with three linked communities, were followed-up as part of the surveillance strategy. An additional three communities with a seroprevalence ≥25.0% but no Ct infection were also followed up ("antibody and infection trigger" investigations). DBS were taken from all residents aged ≥1 year and ocular swabs from all children aged 1-9 years. There was evidence of transmission in the group of communities visited in one district (Zabzugu-Tatale). There was no or little evidence of continued transmission in other districts, suggesting previous infection identified was transient or potentially not true ocular Ct infection. CONCLUSIONS/SIGNIFICANCE: There is evidence of heterogeneity in Ct transmission dynamics in northern Ghana, even 10 years after wide-scale MDA has stopped. There is added value in monitoring Ct infection and anti-Ct antibodies, using these indicators to interrogate past or present surveillance strategies. This can result in a deeper understanding of transmission dynamics and inform new post-validation surveillance strategies. Opportunities should be explored for integrating PCR and serological-based markers into surveys conducted in trachoma elimination settings. |
Precision of Serologic Testing from Dried Blood Spots Using a Multiplex Bead Assay
Gwyn S , Aragie S , Wittberg DM , Melo JS , Dagnew A , Hailu D , Tadesse Z , Haile M , Zeru T , Nash SD , Arnold BF , Martin DL , Keenan JD . Am J Trop Med Hyg 2021 105 (3) 822-827 Multiplex bead assays (MBAs) for serologic testing have become more prevalent in public health surveys, but few studies have assessed their test performance. As part of a trachoma study conducted in a rural part of Ethiopia in 2016, dried blood spots (DBS) were collected from a random sample of 393 children aged 0 to 9 years, with at least two separate 6-mm DBS collected on a filter card. Samples eluted from DBS were processed using an MBA on the Luminex platform for antibodies against 13 antigens of nine infectious organisms: Chlamydia trachomatis, Vibrio cholera, enterotoxigenic Escherichia coli, Cryptosporidium parvum, Entamoeba histolytica, Camplyobacter jejuni, Salmonella typhimurium Group B, Salmonella enteritidis Group D, and Giardia lamblia. Two separate DBS from each child were processed. The first DBS was run a single time, with the MBA set to read 100 beads per well. The second DBS was run twice, first at 100 beads per well and then at 50 beads per well. Results were expressed as the median fluorescence intensity minus background (MFI-BG), and classified as seropositive or seronegative according to external standards. Agreement between the three runs was high, with intraclass correlation coefficients of > 0.85 for the two Salmonella antibody responses and > 0.95 for the other 11 antibody responses. Agreement was also high for the dichotomous seropositivity indicators, with Cohen's kappa statistics exceeding 0.87 for each antibody assay. These results suggest that serologic testing on the Luminex platform had strong test performance characteristics for analyzing antibodies using DBS. |
Determining seropositivity-A review of approaches to define population seroprevalence when using multiplex bead assays to assess burden of tropical diseases
Chan Y , Fornace K , Wu L , Arnold BF , Priest JW , Martin DL , Chang MA , Cook J , Stresman G , Drakeley C . PLoS Negl Trop Dis 2021 15 (6) e0009457 BACKGROUND: Serological surveys with multiplex bead assays can be used to assess seroprevalence to multiple pathogens simultaneously. However, multiple methods have been used to generate cut-off values for seropositivity and these may lead to inconsistent interpretation of results. A literature review was conducted to describe the methods used to determine cut-off values for data generated by multiplex bead assays. METHODOLOGY/PRINCIPAL FINDINGS: A search was conducted in PubMed that that included articles published from January 2010 to January 2020, and 291 relevant articles were identified that included the terms "serology", "cut-offs", and "multiplex bead assays". After application of exclusion of articles not relevant to neglected tropical diseases (NTD), vaccine preventable diseases (VPD), or malaria, 55 articles were examined based on their relevance to NTD or VPD. The most frequently applied approaches to determine seropositivity included the use of presumed unexposed populations, mixture models, receiver operating curves (ROC), and international standards. Other methods included the use of quantiles, pre-exposed endemic cohorts, and visual inflection points. CONCLUSIONS/SIGNIFICANCE: For disease control programmes, seropositivity is a practical and easily interpretable health metric but determining appropriate cut-offs for positivity can be challenging. Considerations for optimal cut-off approaches should include factors such as methods recommended by previous research, transmission dynamics, and the immunological backgrounds of the population. In the absence of international standards for estimating seropositivity in a population, the use of consistent methods that align with individual disease epidemiological data will improve comparability between settings and enable the assessment of changes over time. |
High Pgp3 Chlamydia trachomatis seropositivity, pelvic inflammatory disease and infertility among women, National Health and Nutrition Examination Survey, United States, 2013-2016
Anyalechi GE , Hong J , Danavall DC , Martin DL , Gwyn SE , Horner PJ , Raphael BH , Kirkcaldy RD , Kersh EN , Bernstein KT . Clin Infect Dis 2021 73 (8) 1507-1516 BACKGROUND: Chlamydia trachomatis causes pelvic inflammatory disease (PID) and tubal infertility. Pgp3 antibody (Pgp3Ab) detects prior chlamydial infections. We evaluated for an association of high chlamydial seropositivity with sequelae using a Pgp3Ab multiplex bead array (Pgp3AbMBA). METHODS: We performed chlamydia Pgp3AbMBA on sera from women 18-39 years old participating in the 2013-2016 National Health and Nutrition Examination Survey (NHANES) with urine chlamydia nucleic acid amplification test results. High chlamydial seropositivity was defined as a median fluorescence intensity (MFI ≥ 50,000; low-positive was MFI > 551-<50,000. Weighted US population high-positive, low-positive, and negative Pgp3Ab chlamydia seroprevalence and 95% confidence intervals (95% CI) were compared for women with chlamydial infection, self-reported PID, and infertility. RESULTS: Of 2,339 women aged 18-39 years, 1,725 (73.7%) had sera and 1,425 were sexually experienced. Overall, 104 women had high positive Pgp3Ab (5.4% [95% CI 4.0-7.0] of US women); 407 had low positive Pgp3Ab (25.1% [95% CI 21.5-29.0]), and 914 had negative Pgp3Ab (69.5% [95% CI 65.5-73.4]).Among women with high Pgp3Ab, infertility prevalence was 2.0 (95% CI 1.1-3.7) times higher than among Pgp3Ab-negative women (19.6% [95% CI 10.5-31.7] versus 9.9% [95% CI 7.7-12.4]). For women with low Pgp3Ab, PID prevalence was 7.9% (95% CI 4.6-12.6) compared to 2.3% (95% CI 1.4-3.6) in negative Pgp3Ab. CONCLUSIONS: High chlamydial Pgp3Ab seropositivity was associated with infertility although small sample size limited evaluation of an association of high seropositivity with PID. In infertile women, Pgp3Ab may be a marker of prior chlamydial infection. |
No Serological Evidence of Trachoma or Yaws Among Residents of Registered Camps and Makeshift Settlements in Cox's Bazar, Bangladesh
Cooley GM , Feldstein LR , Bennett SD , Estivariz CF , Weil L , Bohara R , Vandenent M , Mainul Hasan A , Akhtar MS , Uzzaman MS , Billah MM , Conklin L , Ehlman DC , Asiedu K , Solomon AW , Alamgir A , Flora MS , Martin DL . Am J Trop Med Hyg 2021 104 (6) 2031-2037 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. |
Comparison of platforms for testing antibodies to Chlamydia trachomatis antigens in the Democratic Republic of the Congo and Togo
Gwyn S , Awoussi MS , Bakhtiari A , Bronzan RN , Crowley K , Harding-Esch EM , Kassankogno Y , Kilangalanga JN , Makangila F , Mupoyi S , Ngondi J , Ngoyi B , Palmer S , Randall JM , Seim A , Solomon AW , Stewart R , Togbey K , Uvon PA , Martin DL . Sci Rep 2021 11 (1) 7225 Trachoma, caused by repeated ocular infection with Chlamydia trachomatis (Ct), is targeted for elimination as a public health problem. Serological testing for antibodies is promising for surveillance; determining useful thresholds will require collection of serological data from settings with different prevalence of the indicator trachomatous inflammation-follicular (TF). Dried blood spots were collected during trachoma mapping in two districts each of Togo and Democratic Republic of the Congo. Anti-Ct antibodies were detected by multiplex bead assay (MBA) and three different lateral flow assays (LFA) and seroprevalence and seroconversion rate (SCR) were determined. By most tests, the district with > 5% TF (the elimination threshold) had five-sixfold higher seroprevalence and tenfold higher SCR than districts with < 5% TF. The agreement between LFA and MBA was improved using a black latex developing reagent. These data show optimization of antibody tests against Ct to better differentiate districts above or below trachoma elimination thresholds. |
Integrated survey methodologies for neglected tropical diseases
Harding-Esch EM , Brady MA , Angeles CAC , Fleming FM , Martin DL , McPherson S , Hurtado HM , Nesemann JM , Nwobi BC , Scholte RGC , Taleo F , Talero SL , Solomon AW , Saboyá-Díaz MI . Trans R Soc Trop Med Hyg 2020 115 (2) 124-126 The 2021-2030 Neglected Tropical Diseases road map calls for intensified cross-cutting approaches. By moving away from vertical programming, the integration of platforms and intervention delivery aims to improve efficiency, cost-effectiveness and programme coverage. Drawing on the direct experiences of the authors, this article outlines key elements for successful integrated surveys, the challenges encountered, as well as future opportunities and threats to such surveys. There are multiple advantages. Careful planning should ensure that integration does not result in a process that is less efficient, more expensive or that generates data driving less reliable decisions than conducting multiple disease-specific surveys. |
- Page last reviewed:Feb 1, 2024
- Page last updated:Apr 22, 2024
- Content source:
- Powered by CDC PHGKB Infrastructure