BACKGROUND:The END Fund's Field Entomology Mentorship Program addresses a critical gap in trained entomologists supporting onchocerciasis elimination in Africa. Unlike conventional training, this hands-on mentorship equips early to mid-career entomologists with technical expertise in critical onchocerciasis blackfly surveillance activities. METHODS:The 3-y program follows a phased approach, gradually increasing mentees' independence while ensuring strong mentorship. RESULTS:In its inaugural year, six mentees engaged in field activities across multiple countries, contributing to the development of elimination strategies, onchocerciasis surveillance and research projects. Mentees highlight the program's transformative impact, fostering leadership, collaboration and strategic problem-solving. Their experiences with their mentors have strengthened national program capacity and the program is building a network of skilled experts dedicated to disease elimination. CONCLUSIONS:As the program evolves, mentees will take on more independent roles, ensuring sustainable expertise at the country level. This initiative underscores the importance of investing in local entomological capacity to accelerate onchocerciasis elimination efforts across Africa and other endemic countries.

Background The current global aim for onchocerciasis is to eliminate transmission of infection by administering ivermectin once a year or biannually. However, when ivermectin treatment is given annually for 9-10 y, some individuals still carry low microfilariae (mf) levels, which may allow continued transmission. Methods At four different times (0, 8, 90, 365 days) after treatment with ivermectin, 1608 newly emerged Simulium sanctipauli (Pra form) flies were fed on 35 volunteers, with initial dermal microfilarial loads ranging from 0 to >30 Onchocerca volvulus mf/mg skin. Ten days after feeding, the number and load of mf in these flies were assessed by dissection. Results Notably, even at the lowest skin-snip mf densities-including those showing zero infection-flies can still ingest O. volvulus mf and become infected; 29% of the 1608 fed flies picked up mf. The lowest skin mf levels were recorded on Day 90 after treatment, at which time vector mf uptake increased by 21% with every unit increase in skin mf density (P < .000). Conclusions Very low dermal mf levels can still support parasite transmission. Consequently, widespread low O. volvulus infection in human populations with highly productive vector-breeding sites could significantly affect efforts to eliminate transmission.

Background Having a Simulium vector distribution map is important for all entomological and epidemiological aspects for the elimination of onchocerciasis. Developing these maps using topographic maps has some limitations such as identifying the exact locations of rapids, especially with low-scale maps. This leads to breeding sites being missed during prospecting. Recent efforts to map breeding sites involve the development of technologies such as satellite images, remote sensing modelling and drones. The limitations of these technologies include cost, security concerns and tree cover preventing the observation of rapids from the sky. Although community support has traditionally been used to guide entomological teams during prospecting for breeding sites, community knowledge has not been an integral part in planning breeding site surveys.Methods This article proposes a concept of using community knowledge and health system structure for planning and implementation of breeding sites surveys. The approach uses questionnaires to gather information on fast-flowing stretches of rivers within communities. Using this information, a breeding site survey plan is developed at the national level and reviewed and implemented at the district and subdistrict levels using discussions, photos and videos of fast flowing rivers, as well as topographic maps. A working timetable is then developed that indicates areas to visit each day, maximizing time in the field and other logistics.Conclusions Using health system structures and community members not only provides a rapid approach for entomological surveys but also strengthens entomological fieldwork and fosters community engagement in vector surveillance.

This article reviews the major events that entomology has played, and still plays, in the history of onchocerciasis ('river blindness') from life-cycle discovery to the current global goal of elimination of parasite transmission in all endemic areas. The identified events include the various attempts to implement successful vector control, the important introduction of the microfilaricide ivermectin and the new improvements in laboratory-based techniques to identify infected blackflies and refine onchocerciasis epidemiology and programme monitoring. These scientific events are paralleled with the development of a series of increasingly ambitious public health targets, first to reduce blindness due to this infection, then to reduce the prevalence of all the clinical symptoms (ocular and dermatological disease) and, finally, in more recent times, to interrupt actual transmission of the parasite. Five major areas of onchocerciasis-related entomology (i.e. the effects of fly biting; vector competence and migration; epidemiology; vector control; and management of elimination programmes) illustrate the importance of entomology to achieving success in eliminating the transmission of Onchocerca volvulus; success that has already been achieved in four countries in Latin America and now in one country in Africa (Niger, 2024), the continent where the vast majority of remaining endemicity is found.

Background River blindness, caused by Onchocerca volvulus and transmitted by Simulium damnosum s.l., requires robust and ethical vector surveillance for its elimination. The human landing catch (HLC) remains the gold standard for collecting blackflies but presents ethical and operational challenges. This review evaluates alternative blackfly collection methods in relation to their effectiveness, consistency, operational feasibility and alignment with a target product profile (TPP) framework for field programmatic use.Methods Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews guidelines, PubMed, Web of Science, WHO IRIS, Scopus and Google Scholar were searched through June 2024 using terms related to blackfly traps, vector collection and onchocerciasis. Peer-reviewed and selected grey literature in English and French was included. Data were thematically synthesised and grouped by trap type, assessing performance against defined TPP criteria.Results Fifteen studies met inclusion criteria. The Esperanza window trap (EWT) and host decoy trap (HDT) achieved high catches in some settings, occasionally matching or surpassing HLC performance, though results varied by ecology. Modified HLC methods reduced exposure while maintaining yields but still required human participation.Conclusions No single alternative method consistently matched HLC across settings; however, optimized EWT and HDT designs show promise for ethical, effective onchocerciasis surveillance.

BACKGROUND:Former Onchocerciasis Control Programme countries like Senegal have made important progress towards eliminating onchocerciasis. Senegal has engaged in post-mass drug administration (MDA) activities, mainly entomological surveillance, but the country initially struggled to collect the recommended number of blackflies in all the country's transmission zones. Here, we implemented a simple approach in the entomological surveillance protocol to increase the number of Simulium damnosum collected. METHODS:The study was conducted over two consecutive years, 2022 and 2023, in the main S. damnosum capture points located along the Gambie and Falémé river basins. We reviewed environmental data, analysed and interpreted previous blackflies capture data and processed field visits to identify optimal periods of blackfly capture in each capture point. RESULTS:After the implementation of our approach, the number of blackflies captured increased by approximately 42% in 2023 compared with 2022 captures. The numbers of blackflies captured increased from 71 999 and 23 666, respectively, in Gambia and Falémé in 2022, to 101 276 and 34 780 in 2023. CONCLUSION:Our results reveal that simple and effective microplanning of blackfly capture periods can support onchocerciasis post-MDA surveillance activities by increasing the number of blackflies captured.

As countries progress from control of onchocerciasis as a public health problem to elimination of parasite transmission, more evidence on vector-related activities and transmission assessments is needed to inform WHO guidelines and country strategies to achieve the targets of the 2030 NTD Roadmap. For vector-borne diseases, entomology plays a critical role in the elimination and verification of transmission based on vector infectivity. The vector-control based Onchocerciasis Control Programme in West Africa (OCP, 1974–2002), had accumulated relevant experience and data. The African Programme for Onchocerciasis Control (APOC, 1995–2015) extended onchocerciasis control, based primarily on mass ivermectin administration, to all African endemic countries, and supported many implementation research projects. OCP and APOC documents, previously available only in hard-copy from OCP or APOC, are now accessible in the WHO Institutional Repository for Information Sharing (WHO IRIS). Most documents cover numerous topics and include large amounts of unpublished data. Here, we provide an overview of the OCP and APOC documents in IRIS. We reviewed and summarized the documents in WHO IRIS as a resource to guide current elimination efforts. We also provided examples for potential uses of the information for mapping, diagnostics, entomology and social science research to the preparation of elimination dossiers. The APOC Collection included 8150 documents. Of these, 3895 were in English and 4194 in French. Topics covered in the documents include CDTi, cytotaxonomy, diagnosis, drug effectiveness, environmental modification, epidemiology, health economics, impact assessment, insecticide resistance, larviciding, mapping, programme implementation, slash and burn, transmission assessment and vector control. The APOC Collection in WHO IRIS makes the wealth of OCP and APOC experience and data available to the onchocerciasis control/elimination and research community.

Background Onchocerciasis (river blindness), caused by the filarial nematode Onchocerca volvulus and transmitted by Simulium blackflies, remains a public health challenge in sub-Saharan Africa. Following the transition from vector control to large-scale ivermectin distribution, microfilariae (mf) prevalence has declined substantially across Ghana. The World Health Organization targets onchocerciasis elimination, defined as sustained mf prevalence below 1%. This requires identifying areas of persistent or resurgent transmission to guide targeted mapping surveys and interventions. Methods A Bayesian spatiotemporal, multilevel, generalized additive model with a zero-inflated beta-binomial outcome was fitted to mf prevalence data from 1353 surveys across 671 villages and environmental and socio-economic predictors. Temporal prevalence trends for ecozones within operational transmission zones (OTZ) were modelled using a 2D spatial smooth to account for residual spatial autocorrelation. Temporal autocorrelation in prevalence was accounted for using a random effect for village nested within ecozone. Results Runoff probability and surface wetness were positively associated with prevalence, consistent with Simulium breeding in fast-flowing water. Despite high initial mf prevalence, by 2015 the median prevalence across all OTZs in Ghana was estimated to be between 0.43 and 1.97%. The probability that prevalence was <1% in 2015 ranged from 0.15 to 0.87. Assuming testing rates and mass drug administration have remained consistent (twice a year and >80% coverage), linear extrapolation predicted that the three OTZs have some probability of exceeding the elimination threshold by 2030, while two were predicted to have near-zero prevalence. The Tano-Ankobra OTZ, which includes both savanna and forest agro-ecological zones, was a persistent hotspot. Conclusions This first comprehensive spatio-temporal analysis of onchocerciasis in Ghana reflects the well-documented challenge of onchocerciasis control in forested riverine environments. Persistent transmission foci in eastern and southern Ghana, particularly in forest zones with sustained vector habitat, warrant targeted investigation and intensified intervention to meet WHO elimination thresholds. ### Competing Interest Statement The authors have declared no competing interest. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study used only openly available human data from Special Project for Elimination of Neglected Tropical Diseases (ESPEN) database portal https://espen.afro.who.int/countries/ghana I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I 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, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data are available online at the ESPEN portal. UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Disease (TDR), P21-0048, B80297 La Trobe University, https://ror.org/01rxfrp27, Graduate Research Scholarship, Full-fee Research Scholarship

Background Large areas in Malawi have not been treated for onchocerciasis. To understand whether to provide treatment in these areas of unknown onchocerciasis endemicity, the Malawi Onchocerciasis Control Program conducted identification and mapping of breeding sites as a prerequisite for onchocerciasis elimination mapping (OEM).Methods The team employed a community knowledge approach using questionnaires and discussions, alongside the standard method of using topographical maps, to plan and implement river prospections for Simulium vector breeding sites.Results A total of 188 sites were prospected from 180 rivers, with 122 sites (67.8%) identified from community information and 58 (32.2%) from topographic maps. Of the 188 sites visited, 30 were positive for Simulium damnosum larvae/pupae and 91 were considered potential breeding sites and need to be visited in a different season for confirmation. A breeding site map for OEM areas was developed. Prospection using this approach lasted for 24 days (approximately eight rivers/day) compared with a previous prospection with the same team that used 12 days to prospect 25 rivers (approximately two rivers/day).Conclusion This demonstrates the potential of using the health system structure and community knowledge for breeding site surveys, shortening the prospection time while effectively identifying fast-flowing rivers and breeding sites.

The current guidelines for stopping treatment and verifying elimination of onchocerciasis recommend entomological and epidemiological surveys to be performed during the peak transmission season, which is generally assumed to occur during the rainy season, although this may not necessarily hold true in all transmission zones (TZs). This review has synthesized data, from a literature search, on the effects of seasonality on transmission in West and Central Africa. Seasonality affects vector population dynamics by altering terrestrial and aquatic ecology. In TZs with perennial rivers, peak transmission and peak vector density may either coincide or occur at different periods. These peaks could occur in either the rainy or the dry season in both forest and savanna zones, and the periods may change between years. Therefore, countries should establish updated local biting patterns at a TZ prior to vector collection. Also, while using peak biting density as a convenient indicator for when to commence vector collection (because of the need for a sufficient sample size), the survey period should include months in both seasons to increase the chances of collecting during peak transmission. Seasonality significantly impacts onchocerciasis transmission elimination; and it also offers critical avenues for effective intervention and transmission evaluation.

Onchocerciasis is a parasitic infection caused by the filarial nematode Onchocerca volvulus and is transmitted through the bites of blackflies of the genus Simulium that breed in rivers and streams. The current WHO definition of transmission zones is limited, leaving country programmes to address challenges such as delineating transmission zones correctly, addressing blackfly migration, managing parasite and host movement and handling cross-border transmission issues. A more data-driven approach to the practical definition of transmission zones in African countries would be advantageous. A review of the documents in the WHO Institutional Repository for Information Sharing (WHO IRIS) and using standard search engines (e.g. PubMed, Google Scholar) has identified previously less recognised factors that could enhance the definition and use of transmission areas in onchocerciasis areas. These guiding observations integrate historical operational, entomological, epidemiological and ecological information with genomic aspects.

Background As countries progress from control of onchocerciasis as a public health problem to elimination of parasite transmission, more evidence on vector-related activities and transmission assessments is needed to inform WHO guidelines and country strategies to achieve the targets of the 2030 Neglected Tropical Disease Roadmap. For vector-borne diseases, entomology plays a critical role in the elimination and verification of transmission based on vector infectivity. The vector control-based Onchocerciasis Control Programme (OCP) in West Africa, 1974-2002, had accumulated relevant experience and data. The African Programme for Onchocerciasis Control (APOC; 1995-2015) extended onchocerciasis control, based primarily on mass ivermectin administration, to all African endemic countries and supported many implementation research projects. OCP and APOC documents, previously available only in hard copy from OCP or APOC, are now accessible in the WHO Institutional Repository for Information Sharing (WHO IRIS). Most documents cover numerous topics and include large amounts of unpublished data. Here, we provide an overview of the OCP and APOC documents in IRIS.Methods We reviewed and summarised the documents in WHO IRIS as a resource to guide current elimination efforts. We also provided examples for potential uses of the information for mapping, diagnostics, entomology and social science research to the preparation of elimination dossiers.Results The APOC Collection included 8150 documents. Of these, 3895 were in English and 4194 in French. Topics covered in the documents include community-directed treatment with ivermectin, cytotaxonomy, diagnosis, drug effectiveness, environmental modification, epidemiology, health economics, impact assessment, insecticide resistance, larviciding, mapping, programme implementation, slash and burn, transmission assessment and vector control.Conclusion The APOC Collection in WHO IRIS makes the wealth of OCP and APOC experience and data available to the onchocerciasis control/elimination and research community.

Current guidelines for onchocerciasis elimination rely heavily upon assessment of the presence of Onchocerca volvulus in the vector Simulium damnosum (sensu lato). This entomological study was conducted over four years in several regions of Burkina Faso to determine the progress made towards interrupting onchocerciasis transmission. Larvae and adult blackflies were collected in eight river basins (Comoé, Léraba, Dienkoa, Mouhoun, Bougouriba, Bambassou, Nakambé, Nazinon and Sissili). Larvae were analyzed by cytotaxonomy, and the adult blackflies analyzed for the presence of infective larvae of O. volvulus by PCR. Blackfly infectivity rates were first determined by year for each basin, then compared to the thresholds established by the WHO. The results indicate that the blackflies collected belong to the savannah group species Simulium damnosum (sensu stricto) and Simulium sirbanum. Hybrids of the two species were also identified. Overall, the prevalence of flies carrying infective larvae was below the threshold of 0.05% established by the WHO, indicating important progress towards the interruption of onchocerciasis transmission in Burkina Faso, although hotspots with infectivity rates well above the WHO's thresholds remain. Onchocerca volvulus continues to be transmitted in six of the nine basins evaluated, all of which border neighboring countries. These data indicate that it will be necessary to maintain entomological surveillance in these hotspot areas until transmission is interrupted throughout the region.

Supplementary Table 6 shows the basic characteristics of EOCRC, LOCRC and healthy controls in UK Biobank.

Supplementary Table 4 shows the list of environmental risk factors and their associations with early-onset colorectal advanced adenomas (EOCRA).

Supplementary Table 5 shows the list of genes and variants and their associations with early-onset colorectal cancer.

Supplementary Materials and Methods shows the literature search strategy, selection criteria, evidence credibility grading criteria, and PRISMA 2020 Checklist.

Supplementary Table 2 shows the quality rating of the included studies.

Supplementary Table 1 shows basic characteristic of the included studies.