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

Integrated serological surveillance of communicable diseases in the Paraguayan Chaco, 2019

Objective

To establish baseline seroprevalence of soil-borne, waterborne, and foodborne diseases and to monitor diseases that are eliminated or on the path to elimination in the Paraguayan Chaco.

Methods

A total of 1 100 school-age children (6-15 years) were tested in urban and rural schools selected for a cross-cutting population-based survey using a two-stage probabilistic sample design in the three departments of the Paraguayan Chaco. Blood samples were taken on filter paper to measure IgG antibodies using a multiplex bead assay. Data collection was carried out through interviews with parents and caregivers. Access to basic sanitation and improved water was assessed. Differences in pathogen seropositivity and seroprotection were estimated by urban and rural areas.

Results

Seroprotection against measles was 62.9% and against rubella was 78.2%. Minimal diphtheria and tetanus seroprotection (≥0.01 IU/ml) was 92.9% and 98.3%, respectively. Seroprotective levels against these four vaccine-preventable diseases significantly decreased with increasing age (p < 0.05). The following pathogens and respective antigens showed significantly higher seroprevalence (p < 0.05) in rural areas compared with urban areas: Cryptosporidium parvum Cp17: 80.4% vs 64.6%, and Cp23: 60.6% vs 44.8%; Giardia lamblia VSP3: 26.9% vs 16.6%; Strongyloides stercoralis NIE: 11.5% vs 4.1%; and Taenia solium T24H: 7.1% vs 1.6%. Seroprevalence for these pathogens was also higher in Indigenous population when compared to non-Indigenous. Basic sanitation conditions showed significant differences (p < 0.05) between rural and urban areas: adobe and soil dwelling floor (65.3% vs 30.2%), use of pit latrine (90.3% vs 44.2%), availability of drainage or septic tank (8.7% vs 55.2%), access to safe water (19.7% vs 44.9%), and water treatment (6.8% vs 32.3%).

Conclusions

We identified high exposure to soil-borne, waterborne, and foodborne diseases in rural areas and Indigenous population in the Paraguayan Chaco. Low seroprotection against measles and rubella alerts about the risk of immunity gaps to maintain elimination targets.

Challenges and Approaches to Establishing Multi-Pathogen Serosurveillance: Findings from the 2023 Serosurveillance Summit

Multiplex-based serological surveillance is a valuable but underutilized tool to understand gaps in population-level exposure, susceptibility, and immunity to infectious diseases. Assays for which blood samples can be tested for antibodies against several pathogens simultaneously, such as multiplex bead immunoassays, can more efficiently integrate public health surveillance in low- and middle-income countries. On March 7-8, 2023 a group of experts representing research institutions, multilateral organizations, private industry, and country partners met to discuss experiences, identify challenges and solutions, and create a community of practice for integrated, multi-pathogen serosurveillance using multiplex bead assay technologies. Participants were divided into six working groups: 1) supply chain; 2) laboratory assays; 3) seroepidemiology; 4) data analytics; 5) sustainable implementation; and 6) use case scenarios. These working groups discussed experiences, challenges, solutions, and research needs to facilitate integrated, multi-pathogen serosurveillance for public health. Several solutions were proposed to address challenges that cut across working groups.

Monitoring of Leishmania transmission in the postelimination phase: The potential of serological surveys

OBJECTIVES

Monitoring of Leishmania transmission is considered a strategic priority for sustaining elimination of visceral leishmaniasis as a public health problem in the Indian subcontinent. The objective of this study was to evaluate whether serological surveys can distinguish between communities with and without Leishmania transmission, and to assess which serological marker performs best.

METHODS

Seven villages were selected from Bihar and Uttar Pradesh state, India, and categorized as either currently endemic (CE), previously endemic (PE) or nonendemic (NE). Blood samples were analyzed with the rK39 RDT, direct agglutination test (DAT), and rK39 ELISA.

RESULTS

Contrary to the rK39 RDT and DAT, the rK39 ELISA showed a significant difference between all three categories of endemicity, with a seroprevalence of 5.21% in CE villages, 1.55% in PE villages, and 0.13% in NE villages. Even when only looking at the seroprevalence among children aged <10 years, the rK39 ELISA was still able to differentiate between villages with and without ongoing transmission.

CONCLUSION

Our findings suggest the rK39 ELISA to be the most promising marker for monitoring of Leishmania transmission. Further validation is required, and practical, context-adapted recommendations need to be formulated in order to guide policymakers toward meaningful and sustainable surveillance strategies in the post-elimination phase.

Integrated Serosurveillance for Onchocerciasis, Lymphatic Filariasis, and Schistosomiasis in North Darfur, Sudan

Sudan is endemic for multiple neglected tropical diseases, including trachoma, onchocerciasis (OV), lymphatic filariasis (LF), and schistosomiasis (SCH). In 2019, dried blood spot samples were collected for a baseline trachoma serosurvey in three localities (El Seraif, Kotom, and Saraf Omrah) in North Darfur State. None were classified previously as OV- or LF-endemic, although low levels of SCH had been identified in all three. Approximately 30 households from 25 communities in each locality were selected by multistage cluster random sampling. Collections of DBSs were analyzed by multiplex bead assay for antibodies to multiple pathogens. This paper presents data on OV (Ov16), LF (Wb123, Bm14, Bm33), and SCH (soluble egg antigen [SEA], Sm25) antibodies among 8,322 individuals from 2,119 households. The survey-adjusted seroprevalence estimates for Ov16 were <0.3% in all localities. Lymphatic filariasis-antigen seroprevalences were discordant. Seroprevalence estimates ranged from 4.6-6.0% (Wb123), 0.99-1.4% (Bm14), and 29.2-33.3% (Bm33). Schistosomiasis seroprevalence estimates among school-aged children ranged from 2.7-8.0% (SEA) and 10.9-15.6% (Sm25). Ov16 seropositivity was low and supported the localities' classification as nonendemic. The results suggested LF exposure, but discordance between antigens, challenges defining seropositivity thresholds, and the absence of programmatic guidance based on antibody serology alone for Wuchereria bancrofti indicate a need for remapping surveys to confirm transmission. Schistosomiasis antibody levels were high enough to warrant further mapping to guide treatment decisions. The lack of gold standards limited interpretation of results, particularly for LF, but in resource-challenged areas, integrated serological surveillance offers the possibility of efficient monitoring of exposure to multiple diseases.

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.