Reaching the last mile: main challenges relating to and recommendations to accelerate onchocerciasis elimination in Africa

The use of quantitative clinical pharmacology approaches to support moxidectin dosing recommendations in lactation

Moxidectin is approved by the US Food and Drug Administration (US FDA) for the treatment of onchocerciasis (river-blindness) due to Onchocerca volvulus in patients aged 12 years and older. In onchocerciasis-endemic areas, mass drug administration (MDA) programs with ivermectin, with or without vector control, aim to control the disease, reduce morbidity, interrupt transmission, and more recently, achieve elimination. Moxidectin has the potential to be used in MDA programs. In countries where onchocerciasis is endemic, infants are often breastfed up to the age of 2 years, suggesting that some women are likely to be lactating during such periodic MDA programs. Quantitative analyses of non-clinical and clinical data using non-compartmental analysis and population based pharmacokinetic (popPK) modeling as well as physiologically based pharmacokinetic modeling (PBPK) were performed to determine the amount of moxidectin excreted in breast milk and subsequent exposures in the infant. The results of the analyses were similar. Concentrations of moxidectin in breast milk followed a similar pattern to those in plasma, with maximum concentrations occurring approximately 4 hours after dosing followed by a rapid decline in both breast milk and plasma. As early as two days after dosing, concentrations of moxidectin in breast milk were below the threshold for acceptable daily intake levels established by the European Medicines Agency (EMA) and FDA for secondary exposures from veterinary use, and below the WHO recommended relative infant dose (RID) safety threshold. The analyses were conducted to support prescribers and policy makers on dosing recommendations for moxidectin in lactation.

Community Involvement in Onchocerciasis Post-elimination Surveillance in Bududa District, Eastern Uganda: A cross-sectional study

BACKGROUND

Globally, there are an estimated 20.9 million cases of onchocerciasis, with Africa bearing the greatest burden. The World Health Organization (WHO) has targeted the disease for elimination by 2030. As of August 2023, there were 15 foci in 37/48 (76%) districts and one city in Uganda that had reached the elimination phase. However, there is a paucity of data on community involvement in post-elimination surveillance (PES) activities. The communities in the post-elimination phase are expected to maintain surveillance, provide health education, refer cases for treatment, and participate in surveillance. However, it is not clear whether this is being done. In this study, we assessed the feasibility of community involvement in post-elimination surveillance activities in Bududa District, Eastern Uganda, to draw key generalisable lessons for similar settings.

METHODS

This was a cross-sectional study employing rigorous mixed methods of data collection. We used a semi-structured questionnaire to collect quantitative data on randomly sampled study participants in two sub-countries in the district. Community involvement in post-elimination surveillance (PES) was our dependent variable, measured using Yes or No questions, and our independent variables were measured on different scales. Computations of proportions and associations were done using Stata 15 software. Conversely, qualitative data were collected via focus group discussions (FGDs) for community participants and key informant interviews (KIIs) for local leaders. For the qualitative component, we had 2 FGDs, each consisting of 8 gender-balanced participants per group and 8 KIIs. Qualitative data analyses were done using a robust thematic framework approach, ensuring the reliability and validity of our findings.

RESULTS

A total of 422 participants with a mean age of 51.4 years (SD = 15.8) participated in the study. Community involvement in post-elimination surveillance was low (14%). Factors associated with involvements were district support [Adjusted odd ratio AOR 14, 95 CI = (2.5, 81.7)], seeing black flies in the environment in a week preceding the survey [AOR 8, 95% CI = (1.5, 42.5)], in one month [AOR 3.8, 95% CI = (1.1, 13.2)], and being a community volunteer in the Ivermectin treatment program [AOR 4.3, 95% CI = (1.03, 17.9)]. Lack of funding, poor motivation, poor program sustainability planning, and a lack of drugs at health facilities were key challenges affecting community involvement in post-elimination surveillance.

CONCLUSION

Community involvement in onchocerciasis post-elimination surveillance activities in Bududa District in Eastern Uganda was low but could be improved by increased district support, funding, community motivation and sensitisation.

Gastrointestinal parasitic infections: Prevalence and risk factors in West Ismailia, Arab Republic of Egypt

BACKGROUND

This study aimed to determine the prevalence of gastrointestinal parasites (GIP) in the rural community of West Ismailia and its associated risk factors. Human infection by GIP is natural and expected. There are few records concerning parasitic infection in the rural areas of the Ismailia Governorate.

METHODS

From 520 individuals, sociodemographic and risk factors information were retrieved. Fecal samples were collected, concentrated, and tested for GIP infection using a microscopic examination.

RESULTS

The West Ismailia study population had a 40.4% prevalence of GIP infection, including single and concomitant parasite infections. The most common cause of GIP infection was protists (38%). Entamoeba sp., Blastocystis sp., and G. duodenalis were the most common parasites. Poly-parasitism was prevalent within the West Ismailia region. Age, abdominal symptoms, perianal itching, ownership of numerous animal species, exposure to turbid water, previous parasitic infection (PPI), and non-treatment reception of PPI were all considered significant factors associated with GIP infection. Specific individuals from the same family have been observed to have identical GIP.

CONCLUSION

GIP infection remains underestimated in rural areas. Periodic screening and treatment for GIP infection in children and public education on GIP hazards and prevention, focusing on personal hygiene, are recommended. Family members of affected individuals should be screened and treated for GIP.

Onchocerciasis in the Cameroon-Chad border area after more than 20 years of annual mass ivermectin distribution

BACKGROUND

The main vectors of onchocerciasis in Africa are Simulium damnosum sensu lato, which transmit the causative agent Onchocerca volvulus. The force of transmission is driven by the vector density, hence influencing the disease prevalence and intensity. Onchocerciasis is currently targeted for elimination using mass drug administration (MDA) of ivermectin, a potent microfilaricide. MDA in Cameroon began in 1987 in the Vina Valley, an endemic cross-border area with Chad, known for high vector densities and precontrol endemicity. Evaluations in 2008-2010 in this area showed ongoing transmission, while border areas in Chad were close to interrupting transmission. This study aimed to evaluate transmission in this area after several rounds of MDA since the last evaluation surveys.

METHODS

Black flies were collected by human landing catches at seven border sites in Cameroon, twice a week, from August 2021 to March 2022. A fraction of the flies was dissected for parity assessment and identification of Onchocerca larval stages. The transmission indices were estimated. Black fly larvae were also collected from the breeding sites at the fly catching sites and identified to species level by cytotaxonomy.

RESULTS

A total of 14,303 female flies were collected, and 6918 were dissected. Of these, 4421 (64.0%) were parous. The total biting rates were high, reaching up to 16,407 bites/person/study period, and transmission potential (third-stage larvae (L3) from head/all L3) were 367/702, 146/506, 51/55, 20/32, 0/3, 0/0, and 0/0 infective larvae/person, respectively, for Mbere-Tchad, Babidan, Hajam/V5, Gor, Djeing, Touboro, and Koinderi. Infectivity rates (L3 from head) were 16.00, 12.75, 5.15, and 4.07 infective females (L3H)/1000 parous flies for Haijam, Mbere-Tchad, Babidan, and Gor, respectively. These values exceed the World Health Organization (WHO) thresholds of ≤ 20 annual transmission potential (ATP) or < 1 infective female/1000 parous females. The major vectors identified were Simulium damnosum sensu stricto, S. squamosum, and for the first time in the area, S. yahense.

CONCLUSIONS

More than 20 years of MDA has not eliminated onchocerciasis in the study area; hence, this area is a potential source of reintroduction of onchocerciasis in Chad and would require alternative treatment strategies. Many factors such as MDA efficiency, effectiveness of ivermectin, and cytospecies composition may be contributing to transmission persistence.

Differential susceptibility of Onchocerca ochengi adult male worms to flubendazole in gerbils and hamsters

Onchocerciasis is a devastating skin and eye disease that afflicts about 21 million people, most of whom live in sub-Saharan Africa. Its control with the microfilaricidal drug ivermectin is limited, thus necessitating the development of preclinical animal models to aid in the discovery of a macrofilaricide. Previously, we found that Onchocerca ochengi (the closest relative of the human O. volvulus) worm masses survive better in hamsters than in gerbils. The aim of this study was to compare the survival of O. ochengi adult male worms and their susceptibility to flubendazole (FBZ, a macrofilaricide) in gerbils and hamsters. The animals were intraperitoneally implanted with O. ochengi male worms, treated with FBZ, and sacrificed 35 days post-implantation. Unlike gerbils which had some worms moving freely in the peritoneum and some in newly formed nodules (neo-nodules), all the worms in the hamsters were found in neo-nodules. FBZ significantly decreased worm burden, motility, and viability in gerbils whereas it had no significant effect in hamsters. These results highlight a major difference in how O. ochengi adult male worms are sustained and affected by FBZ in gerbils compared to hamsters. Understanding the difference between these two models is important in the development of effective macrofilaricides for onchocerciasis.

Progress towards elimination of onchocerciasis in the Region du Sud-Ouest of Burkina Faso which was previously subject to a recrudescence event after vector control

BACKGROUND

The Sud-Ouest region of Burkina Faso (especially the Bougouriba valley) has been historically problematic with respect to onchocerciasis control, with a recrudescence of infections after vector control carried out the WHO Onchocerciasis Control Programme was halted in 1989. After 1996, mass drug administration of ivermectin was instigated to control the recrudescence so that it would no longer constitute a public health problem. However, in 2010 WHO changed its recommended policy from control to elimination, and in 2013 biannual Community-Directed Treatment with Ivermectin (CDTI) was instigated. Epidemiological surveys were carried-out in 2011 and 2018 to determine whether CDTI was producing a decline in infection levels and progress towards elimination.

METHODOLOGY/PRINCIPAL FINDINGS

A cross-sectional study was conducted across 20 villages in four health districts in 2011 and 29 villages in 2018. Individuals aged five years and above were examined by skin-snip, and the prevalence and microfilarial load was determined for each village. In 2011, 75% of villages had some infections and 20% had prevalences >5%, with a mean prevalence across all villages of 2.63% (range 0.0-9.7%), and community microfilarial load ranging from 0 to 0.25 microfilariae per biopsy. In 2018, nine villages (= 31% of total) had some infections, with prevalences ranging from 0.41% to 3.54%, and a mean prevalence across all villages of 0.37%. Community microfilarial load ranged from 0 to 0.1. Amongst those people found to be microfilarial positive, 87% had a history of migration.

CONCLUSIONS/SIGNIFICANCE

The endemicity of onchocerciasis infection in the Sud-Ouest region has declined to low levels and seems to be progressing towards elimination. Our findings indicated that biannual CDTI is having good effect, but it should continue for a number of years to ensure elimination of transmission. However, progress towards elimination has a troublesome history in this region, and it would be advisable to select more sentinel villages to have confidence in any future epidemiological and entomological surveys, especially Stop-MDA surveys. With positive individuals migrating between countries, cross-border collaboration needs more attention to ensure effective treatment for onchocerciasis elimination.

Awareness of and participation in mass drug administration programs used for onchocerciasis control in the Atwima Nwabiagya North District, Ghana

BACKGROUND

Studies on Mass drug administration (MDA) in Ghana targeting various diseases, have mostly focused on factors that affect coverage and compliance to MDA with limited focus on evidence regarding awareness and community perception of the program. Therefore, this study sought to provide empirical evidence on the knowledge of onchocerciasis, and awareness of and participation in the MDA among community members.

METHODS

A community-based cross-sectional survey was conducted from August to October 2019 in communities within the Atwima Nwabiagya North District, Ghana. Data was collected from 2,008 respondents. Bivariate and multivariate logistic regression analyses were performed to measure the associations between socio-demographics, having heard of onchocerciasis and its prevention, and levels of awareness of the MDA program.

RESULTS

A total of 1268 respondents (63.2%) were aware of the MDA program. The majority ofMost respondents (74.4%) were of the view that the information given about the program was not enough and 45.4% of the respondents had no idea about the relevance of the MDA program. Respondents who had ever heard about onchocerciasis prevention and persons who had previously participated in the MDA program were more likely to be aware of the MDA program during implementation (AOR = 2.32; 95% CI 1.79-3.01 and AOR = 9.31; 95% CI 7.06-12.26, respectively).

CONCLUSIONS

We observed a significant association between being aware of MDA campaigns and knowledge of onchocerciasis and its preventive methods, and participation in previous MDA campaigns. We recommend intensification and improvement of prevention campaigns regarding the onchocerciasis MDA program as key to ensuring increased MDA program participation.

Persistence of onchocerciasis and associated dermatologic and ophthalmic pathologies after 27 years of ivermectin mass drug administration in the middle belt of Ghana

OBJECTIVES

There is a pressing need to regularly evaluate the progress of onchocerciasis elimination programmes to timely identify and mitigate potential risks hindering the reaching of the 2030 targets proposed by the World Health Organization (WHO) in its roadmap on neglected tropical diseases (NTDs). We determined the prevalence of onchocerciasis and associated dermatological and ophthalmological manifestations in six endemic communities in the Bono Region of Ghana after 27 years of ivermectin mass treatment.

METHODS

In a cross-sectional study, 564 participants aged ≥5 years were enrolled (49.1% females), with a median age of 26 (range: 5-89) years. In 54% and 47%, skin-snip microscopy and Ov16 rapid diagnostic tests were performed, respectively. Skin disease was determined using the WHO Skin NTD App. Visual function assessments included tests of visual acuity.

RESULTS

The overall microfilarial prevalence was 12.5% (38/305) and Ov16 seroprevalence was 24.2% (64/265). Severe itching was recorded in 24.3%, acute papular onchodermatitis in 52.8%, chronic papular onchodermatitis in 12.5%, lichenified onchodermatitis in 0.7%, skin atrophy in 11.3%, depigmentation in 1.7% and palpable nodules in 5.3%. Of the 301 persons in which visual acuity was examined, 17% were visually impaired and 5.3% were blind and 47.3% presented with cataract. Chronic papular onchodermatitis, lichenified onchodermatitis, depigmentation and visual impairment were significantly associated with the presence of skin microfilariae and Ov16 seropositivity.

CONCLUSIONS

The persistence of Onchocerca volvulus infection and onchocerciasis-associated dermatological and ophthalmological pathologies after prolonged treatment is of concern. There is a need to include morbidity management in onchocerciasis elimination programmes and understand better patterns of treatment coverage, adherence and actual intake of ivermectin.

The Truman Show for Human Helminthic Parasites: A Review of Recent Advances in In Vitro Cultivation Platforms

Throughout history, parasites and parasitic diseases have been humankind's constant companions, as evidenced by the findings of tapeworm eggs in ancient, mummified remains. Helminths are responsible for causing severe, long-term, and debilitating infectious diseases worldwide, especially affecting economically challenged nations due to prevailing deficits in access to sanitation, proper hygiene practices, and healthcare infrastructure. Socio-ecological drivers, such as poverty, migration, and climate change, continue to contribute to parasites and their disease vectors being spread beyond known endemic zones. The study of parasitic diseases has had a fair amount of success leading to the development of new chemotherapeutic agents and the implementation of parasite eradication programs. However, further progress in this direction has been hampered by the challenges of culturing some of these parasites in in vitro systems for efficient availability, basic life cycle, infection studies, and effectiveness of novel treatment strategies. The complexity of the existing models varies widely, depending on the parasite and its life cycle, ranging from basic culture methods to advanced 3D systems. This review aims to highlight the research conducted so far in culturing and maintaining parasites in an in vitro setting, thereby contributing to a better understanding of pathogenicity and generating new insights into their lifecycles in the hopes of leading to effective treatments and prevention strategies. This work is the first comprehensive outline of existing in vitro models for highly transmissible helminth diseases causing severe morbidity and mortality in humans globally.

Gastrointestinal parasites in Africa: A review

Data on human gastrointestinal parasites (GIP) infections in the african sub-regions and countries are mainly lacking in terms of prevalence and population stratification by afflicted age group, symptomatology, multi-parasitism, and diagnostic methods. This study aims to describe the GIP reported in african countries and discuss the extent of the burden in the african context. Only 68.42% (39/57) of african countries reported human cases of GIP with helminths (45%, CI: 40-50%, I²: 99.79%) as the predominant parasitic group infecting the african population. On a regional scale, Central Africa had the highest pooled prevalence for GIP (43%, CI: 32-54%, I²: 99.74%), while the Central African Republic led all countries with a pooled prevalence of 90% (CI: 89-92%, I²: 99.96%). The vulnerable population (patients who are minorities, children, old, poor, underfunded, or have particular medical conditions) was the most affected (50%, CI: 37-62%, I²: 99.33%), with the predominance of GIP in the 6 to <20 years age group (48%, CI: 43-54%, I²: 99.68%). Reports on multi-parasitism (44%, CI: 40-48%, I²: 99.73%) were almost double the reports of single infections (43%, CI: 27-59%, I²: 99.77%) with combined molecular and non-molecular techniques demonstrating the best performance for GIP identification. The current review spans more than 40 years of GIP reports from the african continent. Geographical characteristics, environmental factors, habits of its inhabitants, and their health status play a crucial role in GIP modulation and behaviour in its captive hosts. Strategies for regular and enhanced surveillance, policy formation, and high-level community awareness are necessary to identify the true incidence in Africa and the transmission of the pathogens via water and food.

Evaluating the impact of alternative intervention strategies in accelerating onchocerciasis elimination in an area of persistent transmission in the West Region of Cameroon

BACKGROUND

Alternative strategies are recommended to accelerate onchocerciasis elimination in problematic areas including areas where annual ivermectin (IVM) distributions are unable to interrupt transmission. The aim of this study was to accelerate progress towards elimination in the Massangam health district, West Region of Cameroon where impact evaluations demonstrated ongoing transmission of onchocerciasis infection and high microfilaria (mf) prevalence despite more than 20 years of annual IVM distribution.

METHODOLOGY/PRINCIPAL FINDINGS

Parasitological, entomological, and breeding site surveys were conducted in 2015 delineating a focus of high transmission and identified three communities with high mf prevalence. Individuals in these communities were screened for mf yearly for a period of two years and those positive treated each year with doxycycline 100mg daily for five weeks. In addition, surrounding communities were given biannual IVM. Temephos-based applications were performed once a week for 10 consecutive weeks on Simulium damnosum s.l. breeding sites. Parasitological and entomological assessments were conducted after two years of implementation and findings compared with 2015 baseline. Alternative strategies accelerated progress towards elimination through a significant mf reduction (χ2: 40.1; p<0.001) from 35.7% (95%CI: 29.0-42.8) to 12.3% (95%CI, 9.0-16.4). Reductions were furthermore recorded over a longer period, with a reduction of prevalence of 29.0% under AIS in 2017-2019 compared to 14.6% with IVM in 2011-2015; and by 23.2% following the two years of alternative strategies compared to 20.3% reduction over 15 years of treatment with IVM (1996-2011). Entomological assessment demonstrates that transmission is still ongoing despite the reduction in mf which is expected in an environment with complex breeding sites and open transmission zones, i.e., where migration of flies or humans to and from neighbouring areas is common.

CONCLUSION/SIGNIFICANCE

This study provides evidence that alternative strategies are feasible and effective and should be considered in areas where transmission is sustained throughout long term uninterrupted MDA with IVM. However, there is need to consider wider transmission zones, and further explore optimal timing of larviciding with treatment to impact transmission.

Policy stakeholder perspectives on barriers and facilitators to launching a community-wide mass drug administration program for soil-transmitted helminths

BACKGROUND

Recent evidence suggests that soil-transmitted helminth (STH) transmission interruption may be feasible through community-wide mass drug administration (cMDA) that deworms community members of all ages. A change from school-based deworming to cMDA will require reconfiguring of STH programs in endemic countries. We conducted formative qualitative research in Benin, India, and Malawi to identify barriers and facilitators to successfully launching a cMDA program from the policy-stakeholder perspective.

METHODS

We conducted 40 key informant interviews with policy stakeholders identified as critical change agents at national, state/district, and sub-district levels. Participants included World Health Organization country office staff, implementing partners, and national and sub-national government officials. We used the Consolidated Framework for Implementation Research to guide data collection, coding, and analysis. Heat maps were used to organize coded data and differentiate perceived facilitators and barriers to launching cMDA by stakeholder.

RESULTS

Key facilitators to launching a cMDA program included availability of high-quality, tailored sensitization materials, and human and material resources that could be leveraged from previous MDA campaigns. Key barriers included the potential to overburden existing health workers, uncertainty of external funding to sustain a cMDA program, and concerns about weak intragovernmental coordination to implement cMDA. Cross-cutting themes included the need for rigorous trial evidence on STH transmission interruption to gain confidence in cMDA, and implementation evidence to effectively operationalize cMDA. Importantly, if policy stakeholders anticipate a cMDA program cannot be sustained due to cost and human resource barriers in the long term they may be less likely to support the launch of a program in the short term.

CONCLUSIONS

Overall, policy stakeholders were optimistic about implementing cMDA primarily because they believe that the tools necessary to successfully implement cMDA are already available. Policy stakeholders in this study were cautiously optimistic about launching cMDA to achieve STH transmission interruption and believe that it is feasible to implement. However, launching cMDA as an alternative policy to school-based deworming will require addressing key resource and evidence barriers. Trial registration This study was registered in the U.S. National Library of Medicine Clinical Trials registry (NCT03014167).

Rational design of a novel multi-epitope peptide-based vaccine against Onchocerca volvulus using transmembrane proteins

Almost a decade ago, it was recognized that the global elimination of onchocerciasis by 2030 will not be feasible without, at least, an effective prophylactic and/or therapeutic vaccine to complement chemotherapy and vector control strategies. Recent advances in computational immunology (immunoinformatics) have seen the design of novel multi-epitope onchocerciasis vaccine candidates which are however yet to be evaluated in clinical settings. Still, continued research to increase the pool of vaccine candidates, and therefore the chance of success in a clinical trial remains imperative. Here, we designed a multi-epitope vaccine candidate by assembling peptides from 14 O. volvulus (Ov) proteins using an immunoinformatics approach. An initial 126 Ov proteins, retrieved from the Wormbase database, and at least 90% similar to orthologs in related nematode species of economic importance, were screened for localization, presence of transmembrane domain, and antigenicity using different web servers. From the 14 proteins retained after the screening, 26 MHC-1 and MHC-II (T-cell) epitopes, and linear B-lymphocytes epitopes were predicted and merged using suitable linkers. The Mycobacterium tuberculosis Resuscitation-promoting factor E (RPFE_MYCTU), which is an agonist of TLR4, was then added to the N-terminal of the vaccine candidate as a built-in adjuvant. Immune simulation analyses predicted strong B-cell and IFN-γ based immune responses which are necessary for protection against O. volvulus infection. Protein-protein docking and molecular dynamic simulation predicted stable interactions between the 3D structure of the vaccine candidate and human TLR4. These results show that the designed vaccine candidate has the potential to stimulate both humoral and cellular immune responses and should therefore be subject to further laboratory investigation.

A call for loiasis to be added to the WHO list of neglected tropical diseases

Loiasis, also called African eye worm, is not currently on WHO's list of priority neglected tropical diseases, even though the risk that individuals with high Loa loa microfilarial densities will develop potentially fatal encephalopathy when they take ivermectin has complicated efforts to use mass drug administration for onchocerciasis (river blindness) and lymphatic filariasis control in co-endemic areas. At least 10 million residents of central and west Africa are thought to have loiasis, which causes painful and itchy subcutaneous oedema, arthralgia, and discomfort when adult helminths that are 3-7 cm in length are present under the conjunctiva of the eye. High levels of microfilaraemia are associated with renal, cardiac, neurological, and other sequelae, and an increased risk of death. The public health burden of loiasis could be greatly reduced with expanded use of diagnostic tests, anthelmintic treatment, and control of the Chrysops spp (tabanid flies) vectors that transmit the parasite. Loiasis should be added to the next revision of the WHO neglected tropical disease priority list, not merely because its inclusion will support the elimination of other skin and subcutaneous neglected tropical diseases, but also because of the complications caused by loiasis itself.

WHO Vision 2020: Have We Done It?

BACKGROUND

Eye health has widespread implications across many aspects of life, ranging from the individual to the societal level. Vision 2020: The Right to Sight is an initiative that was conceptualised in 1997 and launched in 1999. It was led by the World Health Organization (WHO) and the International Agency for the Prevention of Blindness (IAPB) in response to the increasing prevalence of blindness. Approximately 80% of the causes of blindness were avoidable. Hence, the initiative set out to eliminate the major causes of avoidable blindness. These included cataract, uncorrected refractive error, trachoma, onchocerciasis, and childhood blindness.

METHODS

An electronic literature search was performed using PubMed, MEDLINE and Embase databases to assess the impacts of the Vision 2020 initiative.

RESULTS AND CONCLUSION

The Vision 2020 initiative was ambitious and was essential in catapulting the issue of avoidable blindness in the spotlight and putting it on the global health agenda. The causes of avoidable blindness remain and have not been eliminated. However, there have been noticeable changes in the distribution of the causes of avoidable blindness since the conception of Vision 2020, and this is mainly due to demographic shifts globally. We highlight some of the remaining challenges to acheiving avoidable blindness including, population size, gender disparities in access to eyecare services, and the professional workforce.

Ivermectin treatment response in two rural villages with a high prevalence of onchocerciasis and epilepsy, Mahenge Tanzania

Background

Despite 20 years of ivermectin mass distribution in the Mahenge area, Tanzania, the prevalence of onchocerciasis and epilepsy has remained high in rural villages.

Objectives

We investigated the efficacy of ivermectin in reducing Onchocerca volvulus microfilariae and predictors for parasitic load following ivermectin treatment in persons with (PWE) and without epilepsy (PWOE).

Methods

Between April and September 2019, 50 PWE and 160 randomly selected PWOE from Msogezi and Mdindo villages participated in a follow-up study. Skin snips were obtained pre (baseline) and three months post-ivermectin treatment.

Results

The overall prevalence of O. volvulus positive skin snips at baseline was 49% (103/210), with no significant difference between PWE (58.0%) and PWOE (46.3%); p=0.197. The overall mean microfilarial density was significantly higher at baseline 1.45(95%CI:0.98-2.04)) than three-month post-ivermectin treatment (0.23(95%CI:0.11-0.37), p<0.001. Three months after ivermectin, the microfilarial density had decreased by ≥80% in 54 (81.8%, 95%CI: 72.3-91.4) of the 66 individuals with positive skin snips at baseline. High microfilarial density at baseline was the only significant predictor associated with higher microfilarial density in the post-ivermectin skin snips.

Conclusion

Our study reports a decrease in microfilarial density following ivermectin treatment in most individuals. Optimizing ivermectin coverage will address the ongoing onchocerciasis transmission in Mahenge.

Evaluation of mass treatment with ivermectin program reach and survey coverage for onchocerciasis elimination in selected endemic areas of Ethiopia

Currently, national governments of onchocerciasis endemic African countries are working towards the elimination of the disease using mass drug administration (MDA) with ivermectin as a primary strategy. Attainment of this goal requires implementation of prolonged high MDA coverage in all endemic areas, and vigilant monitoring and evaluation of the program. This study was thus conducted with the purpose of i) providing estimate of ivermectin coverage, ii) validating the MDA coverage reported through community drug distributors (CDDs), iii) determining the factors associated with MDA coverage, and iv) estimating the difference between MDA program reach and survey coverage rates following MDA campaign carried out in May 2017 in Asosa and Yeki districts in Ethiopia. A community-based cross-sectional study was conducted among 2,824 study participants in Asosa and Yeki districts. A total of 50 kebeles (smallest administrative units) were randomly selected from the two districts. A systematic sampling was employed to select study households from the 50 kebeles. Then, a household member was randomly selected for the interview. Univariate and multivariate logistic regression analysis were used to determine the odds ratio and to observe the associations between the MDA survey coverage and the variables used. Eighty-seven percent (2458/2824) of the respondents from both districts responded that they were offered ivermectin during the May 2017 MDA campaign. At the district level, 1182 individuals from Yeki and 1276 from Asosa, received the drug, that indicate 88.5% and 85.8% MDA program reach in Yeki and Assosa districts, respectively. Whereas, a total of 366 individuals were not offered ivermectin in both study districts. Of these, 47(12.8%), 143(39.1%), and 176(48.1%) did not receive the drug because of program implementation-related reasons, ineligibility criteria, and personal issues, respectively. Of the 1488 and 1336 respondents in Asosa and Yeki, 1272 and 1182 participants took the drug, resulting in survey coverage rate of 85.5% (95% CI: 83.6–87.2%) and 88.5% (95% CI: 86.7–90.1%), respectively. Multivariable logistic regression analysis revealed significantly low survey coverage rate in females (AOR = 0.5, 95%CI: 0.3–0.6; p<0.001) and in those whose age ranges between 15–24 years (AOR = 0.5, 95%CI: 0.3–0.8; p = 0.007) and 25–34 years (AOR = 0.5, 95%CI: 0.3–0.9; p = 0.021) in Asosa. The researchers believe that the current study generated operational evidence on MDA program reach and coverage rates in two study districts in Ethiopia. The survey coverages were lower than the recommended 90% minimum threshold for success. Only Yeki district reached the 90% threshold survey coverage. Both districts had reported higher coverages than the survey estimates (even outside the 95% CI), thus, were not validated. The majority (60.9%) of the reasons for not receiving the drug were related to program implementation and recipients`personal issues. Efforts must therefore be directed to enhance MDA coverage in future rounds via proper MDA planning and implementation, such as allocating adequate time to the MDA activities, health education, and mobilizing of all segments of the population, including adolescents and the youth. The researchers also recommend such studies to be extended to other MDA programs for other neglected tropical diseases (NTDs).

Habitat preference of blackflies in Omo Gibe river basin (southwest Ethiopia): Implications for onchocerciasis elimination and control

Ecological control of blackflies (Simulium damnosum) can be an alternative or additional tool to enhance onchocerciasis elimination efforts. However, limited research is conducted on the ecology of blackflies in Ethiopia. In this study, we determined the habitat preference of blackfly larvae and their relationship with aquatic macroinvertebrate predators in the Omo Gibe river basin of southwest Ethiopia. Environmental and biological data were collected from 150 sampling sites during both dry and wet seasons in 2019. Generalized Linear Models (GLMs) were used to identify factors affecting the occurrence and abundance of S. damnosum larvae. Canonical Correspondence Analysis (CCA) was used to investigate the relationship between environmental and biological variables and the abundance of S. damnosum larvae. The findings of this study indicated the abundance of S. damnosum larvae increased with increasing turbidity, alkalinity and altitude, but decreased with increasing concentrations of five-day Biological Oxygen Demand (BOD5), orthophosphate and magnesium ion. Both the presence and abundance of S. damnosum larvae decreased with the increasing abundance of stonefly larvae (Perlidae). Simulium damnosum larvae were found less likely in the presence of mayfly larvae (Baetidae) and were less abundant where Chironomidae are abundant. In conclusion, the findings of this study showed that the habitat preference of S. damnosum larvae is determined by environmental factors and that the presence and abundance of the larvae are affected by macroinvertebrate predators. It is essential to establish buffer zones as a part of watershed management to retain pollutants and prevent them from entering directly into water courses to improve water quality and the assemblages of macroinvertebrate predators and enhance biocontrol of blackflies.

Drug development for the treatment of onchocerciasis: Population pharmacokinetic and adverse events modeling of emodepside

BACKGROUND

To accelerate the progress towards onchocerciasis elimination, a macrofilaricidal drug that kills the adult parasite is urgently needed. Emodepside has shown macrofilaricidal activity against a variety of nematodes and is currently under clinical development for the treatment of onchocerciasis. The aims of this study were i) to characterize the population pharmacokinetic properties of emodepside, ii) to link its exposure to adverse events in healthy volunteers, and iii) to propose an optimized dosing regimen for a planned phase II study in onchocerciasis patients.

METHODOLOGY / PRINCIPAL FINDINGS

Plasma concentration-time profiles and adverse event data were obtained from 142 subjects enrolled in three phase I studies, including a single-dose, and a multiple-dose, dose-escalation study as well as a relative bioavailability study. Nonlinear mixed-effects modeling was used to evaluate the population pharmacokinetic properties of emodepside. Logistic regression modeling was used to link exposure to drug-related treatment-emergent adverse events (TEAEs). Emodepside pharmacokinetics were well described by a transit-absorption model, followed by a 3-compartment disposition model. Body weight was included as an allometric function and both food and formulation had a significant impact on absorption rate and relative bioavailability. All drug-related TEAEs were transient, and mild or moderate in severity. An increase in peak plasma concentration was associated with an increase in the odds of experiencing a drug-related TEAE of interest.

CONCLUSIONS/SIGNIFICANCE

Pharmacokinetic modeling and simulation was used to derive an optimized, body weight-based dosing regimen, which allows for achievement of extended emodepside exposures above target concentrations while maintaining acceptable tolerability margins.

Ecological assessment of Black Fly (Simuliumdamnosum, Sensulato) breeding sites in two tributaries of Ogun river, Ogun state, Nigeria

Onchocerciasis is a disease transmitted by blackfly vector of the genus Simuliumdamnosum complex having public and socio-economic consequences. The abundance of blackfly is directly linked to fluvial ecosystems in both tropical and non-tropical countries of the world. This study assessed the ecology of blackfly breeding sites in two tributaries of River Ogun located in Olokemeji and Lisa villages, Ogun State. A total of eighteen water samples were collected for physicochemical analysis during high rainfall (May, June and July), low rainfall (August, September and October) and dry season (November and December) with mean rainfall values of 163.17, 88.03 and 8.95 mm, respectively, in both tributaries. Physicochemical parameters such as temperature (^oC), electrical conductivity (EC), pH, total solids (TS), dissolved oxygen (DO), biochemical oxygen demand (BOD), total suspended solids (TSS), hardness (H), sulphate (SO₄), phosphate (PO₄), alkalinity, acidity, nitrate (NO₃) and total dissolved solids (TDS) were analysed using standard laboratory methods. Digestive enzymes were analysed using 1 g of frozen gut of Simulium larvae grounded with 20 ml of 0.067 g of potassium hydrogen and 20 ml of 0.1 M sodium reagent. A total of 766 and 482 samples of Simulium larvae were collected from Olokemeji and Lisa tributaries using Eppendorf tubes. The zooplanktons collected from Olokemeji and Lisa tributary were 904 and 802, while phytoplanktons collected from Olokemeji and Lisa tributary were 635 and 582 during the study period. Data obtained were analysed using both descriptive analysis and T-test. The results obtained for the physicochemical parameters were 28.7 °C, 137.5 µS/cm, 6.3, 248.1 mg/L, 58 mg/L, 108.8 mg/L, 90.8 mg/L, 2.24 mg/L, 2.24 mg/L, 30.76 mg/L, 42.35 mg/L, 1.99 mg/L, 2.07 mg/L and 2.55 mg/L for Temperature, EC, pH, TS, DO, BOD, TSS, H, SO₄, PO₄, alkalinity, acidity, NO₃ and TDS, respectively. There were significant (p < 0.05) differences between the means of EC, pH, TS, TDS, TSS and hardness of Lisa tributary, and water samples were also viewed under an electron microscope for zooplanktons and phytoplanktons. The values of species diversity which were greater than 0.5 indicated that the species were abundant and evenly distributed. There were significant (p < 0.05) differences between the tributaries in all the digestive enzymes except amylase content. The regression analysis between TSS, nitrate, sulphate, phosphate, acidity, hardness, TS, pH and Simulium larvae abundance showed a positive correlation, R² with values of 0.828, 0.994, 0.948, 0.933, 0.986, 0.997, 0.889 and 0.981, respectively. The R² values between Simulium larvae abundance with phytoplanktons and rainfall have values of 0.868 at p < 0.01 and 0.911 at p < 0.05.

Navigating the way to onchocerciasis elimination: the feasibility and affordability of Onchocerciasis Elimination Mapping

BACKGROUND

Onchocerciasis is targeted for elimination of transmission by 2030 in at least 21 countries. To achieve this, recent and accurate data on the extent and intensity of onchocerciasis transmission are required. This will include mapping areas previously unassessed, or remapping of areas that were last visited as part surveys aiming to prevent blindness, not assess transmission in totality. There is near universal acceptance of the need to carry out these mapping reassessments, to achieve equitable and lasting elimination of onchocerciasis transmission. However, there is no consensus on how to conduct onchocerciasis elimination mapping (OEM), and little published data to inform policymakers and programme managers, including on cost.

METHODS

Here, we summarise the methods and cost implications of conducting pilot OEM surveys in Ghana and Nigeria in 2018. We have included a breakdown of costs incurred overall, per person and per implementation unit in each country, as well as detailed analysis of the cost categories and the main cost drivers.

RESULTS

The procurement and logistics of diagnostics accounted for more than one-third of the total cost, a significant cost driver.

CONCLUSIONS

This information will be valuable to policymakers and donors as they seek to prioritise onchocerciasis elimination and plan to complete OEM.

Health-related quality of life and associated factors among Onchocerciasis patients in southeast Nigeria: A cross-sectional comparative study

INTRODUCTION

Onchocerciasis, a neglected tropical disease of public health importance, causes chronic morbidity and severe disability that may impact on health-related quality of life (HRQoL) of the infected people. This study assessed the HRQoL and associated factors among onchocerciasis patients in southeast Nigeria.

METHODS

This was a community-based cross-sectional comparative study. Using a multistage sampling technique, 340 onchocerciasis patients were selected and matched for age and gender with the healthy population in the same neighbourhood. The respondents were interviewed using the short-form-36 (SF-36) questionnaire to determine their HRQoL. WHO Disability Assessment Schedule 2.0 tool (WHODAS 2.0) was used to assess disability in persons with onchocerciasis. Means were compared with independent student t-test while Chi-square test was used to compare proportions. Also, correlation analysis and logistic regression were used in the analyses.

RESULTS

A significantly lower proportion of people living with onchocerciasis had a good quality of life when compared with the healthy subjects (69.4% vs 93.5%, p<0.001). Also, an inverse relationship was seen between disability and quality of life in the onchocerciasis group (r = -0.647, p<0.001). Predictors of poor quality of life among respondents with onchocerciasis were: respondents aged ≥48 years (AOR = 2.5, 95% CI: 1.4-5.0), those with some disability associated with onchocerciasis (AOR = 3.33, 95%CI: 1.4-5.0) and respondents who perceived themselves as a burden to people (AOR = 10, 95%CI: 2.5-20).

CONCLUSION

Onchocerciasis impacted negatively on HRQoL of persons with onchocerciasis when compared with the healthy population. The quality of life of persons affected with onchocerciasis reduces with increasing disability. There is the need to increase community awareness on onchocerciasis to ensure early diagnosis and prompt treatment as this will reduce disability among those affected with the disease thus enhancing their HRQoL.

Implementation Challenges of Community Directed Treatment with Ivermectin Program for Control of Onchocerciasis in Ulanga, Tanzania

Background:

Community drug distributors (CDDs) have a crucial role in distributing ivermectin for onchocerciasis control and prevention. Their roles, experiences and challenges faced in the implementation of community-directed treatment with ivermectin (CDTI) programme could potentially affect coverage, consequently leading to persistent transmission. Therefore, this study aimed to explore the experience and the roles which CDDs plays in implementation of community directed treatment with ivermectin program for onchocerciasis control in Ulanga, Tanzania.

Methods:

A cross-sectional study design was used to collect qualitative data in 2018 in Ulanga district, Tanzania. Five community drug distributors were purposively selected for in-depth interviews. Thematic framework approach for qualitative data analysis was used to generate codes, categories and themes.

Results:

Out of the five community drug distributors interviewed, two had experience of 15 to 20 years on implementation of the community directed treatment with ivermectin programme while the remaining community drug distributors had experience of less than 10 years. The main challenges faced by CDDs in the implementation of the CDTI programme include; the geographical location of the hamlets (hard to reach hamlets), long distances between houses, low compliance of community members to medication due to fear of side effects experienced before and mistrust of methods of dose calculation, short time of drug distribution and absence of people from their households as the exercise was conducted when community members were involved in agricultural activities.

Conclusions:

The challenges faced in the implementation of the CDTI programme could negatively affect the distribution and coverage of ivermectin treatment in the Ulanga district. It's now an opportune time to address the challenges that CDDs are facing in the implementation of the CDTI programme to ensure effective control of onchocerciasis in the district.

Mass drug administration targeting Onchocerca volvulus in Owabi catchment area in Ashanti Region, Ghana: Determinants of drug coverage and drug uptake

Introduction

Achieving high Mass Drug Administration (MDA) coverage and drug uptake are pivotal in the efforts to eradicate onchocerciasis. The present study investigated the extent and predictors of ivermectin MDA coverage and uptake from the individual and healthcare providers' perspectives. The extent of ivermectin distribution and uptake, and the predictors of distribution and uptake were investigated in endemic communities in the Ashanti Region of Ghana.

Methods

A cross-sectional survey was conducted from August to October 2019 in communities within the Atwima Nwabiagya North District. A total of 2008 respondents were interviewed. Data was collected with REDCap mobile App which had an electronic version of the structured questionnaire. Descriptive data was presented in frequency tables, and bivariate and multivariate logistics regression analysis were performed to measure the associations between exposure variables and outcome variables which were received and uptake of MDA drugs.

Results

A total of 1284 (63.9%) respondents did not receive ivermectin during the 2019 MDA programme and more than half of them were not aware of the drug distribution (53.3%). The most common reasons for not ingesting the drug were fear of side effects (47.7%) and not trusting the drug distributors (20.0%). Respondents in the age group 48–57 years (AOR = 1.37; 95%CI: 1.01–2.67), Persons in the high wealth index (AOR = 1.40; 95%CI: 1.11–1.77), Being aware of the MDA programme (AOR = 6.67: 95%CI: 4.76–9.35), MDA being beneficial (AOR = 2.12; 95%CI: 1.54–2.92) participating in previous MDA (AOR = 5.44; 95%CI: 4.25–6.98) and having stayed in the communities for 10 years and above significantly increased the odds of receiving MDA drugs. Previous uptake of MDA drugs (AOR = 10.58; 95%CI: 5.78–19.38) and perception of the MDA drug as beneficial (AOR = 5.25; 95%CI: 2.55–10.82) increased the likelihood of ingesting drugs when received.

Conclusion

The main health system challenge was limited awareness creation regarding MDA. This seems to affect the optimal utilization of the ivermectin MDA intervention. MDA programmes against onchocerciasis eradication should be designed taking into account specific contextual factors to improve implementation outcomes.

Prevalence, Years Lived With Disability, and Time Trends for 16 Causes of Blindness and Vision Impairment: Findings Highlight Retinopathy of Prematurity

BACKGROUND

Cause-specific prevalence data of vision loss and blindness is fundamental for making public health policies and is essential for prioritizing scientific advances and industry research.

METHODS

Cause-specific vision loss data from the Global Health Data Exchange was used. The burden of vision loss was measured by prevalence and years lived with disability (YLDs).

FINDINGS

In 2019, uncorrected refractory error and cataract were the most common causes for vision loss and blindness globally. Women have higher rates of cataract, age-related macular degeneration (AMD), and diabetic retinopathy (DR) than men. In the past 30 years, the prevalence of moderate/severe vision loss and blindness due to neonatal disorders has increased by 13.73 and 33.53%, respectively. Retinopathy of prematurity (ROP) is the major cause of neonatal disorders related vision loss. In 2019, ROP caused 101.6 thousand [95% uncertainty intervals (UI) 77.5-128.2] cases of vision impairment, including 49.1 thousand (95% UI 28.1-75.1) moderate vision loss, 27.5 thousand (95% UI 19.3-36.60) severe vision loss and, 25.0 thousand (95% UI 14.6-35.8) blindness. The prevalence of new-onset ROP in Africa and East Asia was significantly higher than other regions. Variation of preterm birth prevalence can explain 49.8% geometry variation of ROP-related vision loss burden among 204 countries and territories. After adjusting for preterm prevalence, government health spending per total health spending (%), rather than total health spending per person, was associated with a reduced burden of ROP-related vision loss in 2019 (-0.19 YLDs for 10% increment). By 2050, prevalence of moderate, severe vision loss and blindness due to ROP is expected to reach 43.6 (95% UI 35.1-52.0), 23.2 (95% UI 19.4-27.1), 31.9 (95% UI 29.7-34.1) per 100,000 population.

CONCLUSION

The global burden of vision loss and blindness highlights the prevalent of ROP, a major and avoidable cause for childhood vision loss. Advanced screening techniques and treatments have shown to be effective in preventing ROP-related vision loss and are urgently needed in regions with high ROP-related blindness rates, including Africa and East Asia.

A mixed-methods exploration into the resilience of community drug distributors conducting mass drug administration for preventive chemotherapy of lymphatic filariasis and onchocerciasis in Côte d'Ivoire and Uganda

Volunteer community drug distributors (CDDs) have been vital to progress made in the elimination of onchocerciasis and lymphatic filariasis; two neglected tropical diseases amenable to preventive chemotherapy (PC-NTDs). However, formative work in Côte d'Ivoire and Uganda revealed that CDDs can encounter considerable challenges during mass drug administration (MDA). CDDs must be resilient to overcome these challenges, yet little is known about their resilience. This mixed-methods study explored the resilience of CDDs in Côte d'Ivoire and Uganda. The characteristics and experiences of 248 CDDs involved in the 2018 MDAs in Côte d'Ivoire (N = 132) and Uganda (N = 116) were assessed using a micronarrative survey. Thematic analysis of CDDs' micronarratives was used to identify challenges they encountered during MDA. Resilience was assessed using the Connor-Davidson Resilience Scale 25 (CD-RISC-25). Variables from the micronarrative survey found to be individually associated with mean CD-RISC-25 score (P<0.05) through bivariate analyses were included in a multiple linear regression model. Post-hoc, country-specific analyses were then conducted. Thematic analysis showed that CDDs encountered a wide range of challenges during MDA. The aggregate model revealed that CDDs who had positive relationships or received support from their communities scored higher on the CD-RISC-25 on average (P<0.001 for both), indicating higher resilience. These trends were also observed in the country-specific analyses. Mean CD-RISC-25 scores were unaffected by variations in district, age, gender, and length of involvement with the NTD program. Community support during MDA and positive community-CDD relationships appear to be associated with CDDs' personal capacity to overcome adversity. Involving communities and community leadership in the selection and support of CDDs has the potential to benefit their well-being. This study establishes the CD-RISC-25 as a useful tool for assessing the resilience of CDDs. Further research is needed to understand, promote, and support the resilience of this valuable health workforce, upon which NTD programs depend.

Bacteriome Diversity of Blackflies' Gut and Association with Onchocerca volvulus, the Causative Agent of Onchocerciasis in Mbam Valley (Center Region, Cameroon)

Vector control using larvicides is the main alternative strategy to address limits of preventive chemotherapy using ivermectin for the control of onchocerciasis. However, it remains substantially limited by implementation difficulties, ecological concerns and the resistance of vector populations. Therefore, efficient and environmentally safe alternative control strategies are still needed. This study explores the composition of the blackfly bacteriome and its variability in the presence of Onchocerca volvulus infection, in order to determine their potential as a novel vector control-based approach to fight onchocerciasis. An entomological survey of a collection of samples was performed in the Bafia health district, a historical endemic focus for onchocerciasis in Cameroon. A total of 1270 blackflies were dissected and the infection rate was 10.1%, indicative of ongoing transmission of onchocerciasis in the surveyed communities. Sequencing process of blackflies’ gut DNA for bacteria screening revealed 14 phyla and 123 genera, highlighting the diversity of gut blackflies bacterial communities. Eight bacteria formed the core of blackfly bacteriome and Wolbachia was the predominant genus with 73.4% of relative abundance of blackflies’ gut bacterial communities. Acidomonas and Roseanomas genera were significantly abundant among infected blackflies (p = 0.01), whereas other genera such as Brevibacterium and Fructobacillus were associated with the absence of infection (p = 0.0009). Differences in gut bacterial distribution of blackflies according to their infection status by the parasite suggest a causal relationship between the bacteriome composition and the onset of blackflies’ infection by O. volvulus or vice versa. Blackfly native bacteria are then potentially involved in infection by O. volvulus, either by facilitating or preventing the parasite infestation of the vector. These bacteria represent an interesting potential as a biological tool/target for a novel approach of vector control to fight onchocerciasis.

Eliminating onchocerciasis within the Meme River Basin of Cameroon: A social-ecological approach to understanding everyday realities and health systems

BACKGROUND

Onchocerciasis affects some of the world's most marginalized people, perpetuating poverty and inequalities. Mass Drug Administration (MDA) with Ivermectin has taken place within the Meme River basin region in Cameroon for over 15 years. Despite this, onchocerciasis is still prevalent in the region due to existing and emerging contextual challenges. Using a social-ecological approach we explore the everyday realities of communities, highlighting the challenges and potential solutions that could support Neglected Tropical Disease (NTD) programmes when transitioning from control to elimination of onchocerciasis in this highly endemic area and other similar communities.

METHODOLOGY/PRINCIPAL FINDING

In-depth interviews (71) with community members and Community Drug Distributors (CDDs) were conducted to understand current knowledge, attitudes, and behaviours in relation to transmission, prevention and treatment of onchocerciasis. Through application of the social-ecological model, four key themes were identified: 1. Contextual factors on health promotion interventions (Onchocerciasis history and understanding of the disease, prevention and mitigation strategies and MDA experience); 2. Social determinants (poverty and livelihoods, economic and social impacts on CDD volunteers and stigma); 3. Environmental determinants (exposure, housing, occupation and poverty); and 4. health seeking pathways and decision making for treatment (access, cost and preferable treatment routes). We discuss these core and cross cutting themes (gender differences and community participation/ownership) in relation to intersectoral collaboration, gender equity and health systems support, making recommendations for NTD programmes within the context of integrated and interdisciplinary approaches. These include the need for; intersectional and gender analysis at the local level, addressing environmental dimensions of onchocerciasis through integrated and regular health promotion, vector control strategies and access to safe water sources; reflection and action that embeds responses to social and economic barriers to MDA; integrated case detection and management that is responsive to onchocerciasis symptoms and related stigma and a fair and just support network for CDDs.

CONCLUSION/SIGNIFICANCE

NTD programmes need to respond to diverse community circumstances and behaviours. Communities are not a homogeneous risk group and treating them in this way will delay elimination. A deeper understanding of individual needs and their capacity to seek prevention and treatment must be considered if onchocerciasis is to be eliminated and the remaining impacts managed.

Onchocerciasis (river blindness) - more than a century of research and control

This review summarises more than a century of research on onchocerciasis, also known as river blindness, and its control. River blindness is an infection caused by the tissue filaria Onchocerca volvulus affecting the skin, subcutaneous tissue and eyes and leading to blindness in a minority of infected persons. The parasite is transmitted by its intermediate hosts Simulium spp. which breed in rivers. Featured are history and milestones in onchocerciasis research and control, state-of-the-art data on the parasite, its endobacteria Wolbachia, on the vectors, previous and current prevalence of the infection, its diagnostics, the interaction between the parasite and its host, immune responses and the pathology of onchocerciasis. Detailed information is documented on the time course of control programmes in the afflicted countries in Africa and the Americas, a long road from previous programmes to current successes in control of the transmission of this infectious disease. By development, adjustment and optimization of the control measures, transmission by the vector has been interrupted in foci of countries in the Americas, in Uganda, in Sudan and elsewhere, followed by onchocerciasis eliminations. The current state and future perspectives for control, elimination and eradication within the next 20-30 years are described and discussed. This review contributes to a deeper comprehension of this disease by a tissue-dwelling filaria and it will be helpful in efforts to control and eliminate other filarial infections.

The impact of mass drug administration expansion to low onchocerciasis prevalence settings in case of connected villages

Background

The existence of locations with low but stable onchocerciasis prevalence is not well understood. An often suggested yet poorly investigated explanation is that the infection spills over from neighbouring locations with higher infection densities.

Methodology

We adapted the stochastic individual based model ONCHOSIM to enable the simulation of multiple villages, with separate blackfly (intermediate host) and human populations, which are connected through the regular movement of the villagers and/or the flies. With this model we explore the impact of the type, direction and degree of connectedness, and of the impact of localized or full-area mass drug administration (MDA) over a range of connected village settings.

Principal findings

In settings with annual fly biting rates (ABR) below the threshold needed for stable local transmission, persistence of onchocerciasis prevalence can well be explained by regular human traffic and/or fly movement from locations with higher ABR. Elimination of onchocerciasis will then theoretically be reached by only implementing MDA in the higher prevalence area, although lingering infection in the low prevalence location can trigger resurgence of transmission in the total region when MDA is stopped too soon. Expanding MDA implementation to the lower ABR location can therefore shorten the duration of MDA needed. For example, when prevalence spill-over is due to human traffic, and both locations have about equal populations, then the MDA duration can be shortened by up to three years. If the lower ABR location has twice as many inhabitants, the reduction can even be up to six years, but if spill-over is due to fly movement, the expected reduction is less than a year.

Conclusions/Significance

Although MDA implementation might not always be necessary in locations with stable low onchocerciasis prevalence, in many circumstances it is recommended to accelerate achieving elimination in the wider area.

When infected by onchocerciasis worm parasites, people can eventually develop blindness or severe skin morbidity. Over the past decades, in most places with high onchocerciasis prevalence, annual mass drug administration has become freely available for all inhabitants, regardless of their infection status. This policy has been highly successful in decreasing morbidity. For the next aim, to eliminate onchocerciasis, this intervention is now being expanded to lower prevalence locations. We have adapted an existing simulation model of the spread of onchocerciasis to allow us to model settings where multiple villages are connected, through movement of either humans or blackflies, the intermediate host. By this connection, worms could spill over from a high prevalence village to neighbouring villages with lower prevalence. For such situations, we have examined the impact of implementing treatment only in the high prevalence village, or also in one or two lower prevalence villages. We conclude that for elimination of onchocerciasis transmission, treatment in the lower prevalence villages may not actually be needed, but the total duration of mass drug administration in the entire area can be significantly decreased by expanding treatment to these villages.

Compliance to a Five-Year Biannual Ivermectin Treatment for Onchocerciasis Elimination and Its Determinants among Adults in the Bench Maji Zone, Southwest Ethiopia: A Community-Based Cross-Sectional Study

Background

Community-directed treatment with ivermectin twice a year is a major action to control onchocerciasis in endemic countries. Even though the community-directed treatment with ivermectin was proven effective in treating the disease, the level of compliance to the treatment and its contributing factors was not well addressed in our study area. Therefore, the current study was aimed at determining the magnitude of compliance with the five-year (2013-2017 years) biannual ivermectin treatment and its associated factors among adults living in the Bench Maji Zone, Ethiopia.

Methods

A community-based cross-sectional study was done on 572 randomly selected people aged greater than or equal to 15 years. Data were collected by a face-to-face interview. Descriptive statistics were used to summarize descriptive data. Binary logistic regression was done to assess statistical associations. Adjusted odds ratio and its 95% CI were, respectively, used to measure the strength of statistical association and its significance.

Result

Five hundred fifty-three (553) people had participated in the study making the response rate 96.7%. The overall magnitude of compliance to the five-year biannual ivermectin treatment was 361 (65.3%). The results of the multivariable logistic regression showed that age, positive attitude towards community drug distributers' performance, positive attitude towards height measurement for the treatment dose determination, and involvement in community-directed treatment with ivermectin were independently associated with compliance to ivermectin treatment at P value < 0.05.

Conclusions

Even though the Ethiopian government has set a goal to eliminate onchocerciasis through community-directed treatment with the ivermectin, which is proven effective in treating the disease, the magnitude of compliance with the treatment among adults aged ≥15 years in the Semen Bench District is still unacceptably low. The Bench Maji Zonal Health Department and other stakeholders working on onchocerciasis prevention, control, and elimination should give due emphasis to behavioral change communication through community-based education and other social media to promote community's awareness on community-directed treatment with ivermectin giving due focus to adults aged 45 years and above.

Where are all the anthelmintics? Challenges and opportunities on the path to new anthelmintics

Control of helminth parasites is a key challenge for human and veterinary medicine. In the absence of effective vaccines and adequate sanitation, prophylaxis and treatment commonly rely upon anthelmintics. There are concerns about the development of drug resistance, side-effects, lack of efficacy and cost-effectiveness that drive the need for new classes of anthelmintics. Despite this need, only three new drug classes have reached the animal market since 2000 and no new classes of anthelmintic have been approved for human use. So where are all the anthelmintics? What are the barriers to anthelmintic discovery, and what emerging opportunities can be used to address this? This was a discussion group focus at the 2019 8th Consortium for Anthelmintic Resistance and Susceptibility (CARS) in Wisconsin, USA. Here we report the findings of the group in the broader context of the human and veterinary anthelmintic discovery pipeline, highlighting challenges unique to antiparasitic drug discovery. We comment on why the development of novel anthelmintics has been so rare. Further, we discuss potential opportunities for drug development moving into the 21st Century.

Loop-Mediated Isothermal Amplification as Point-of-Care Diagnosis for Neglected Parasitic Infections

The World Health Organisation (WHO) has placed twenty diseases into a group known as neglected tropical diseases (NTDs), twelve of them being parasitic diseases: Chagas’ disease, cysticercosis/taeniasis, echinococcosis, food-borne trematodiasis, human African trypanosomiasis (sleeping sickness), leishmaniasis, lymphatic filariasis, onchocerciasis (river blindness), schistosomiasis, soil-transmitted helminthiasis (ascariasis, hookworm, trichuriasis), guinea-worm and scabies. Such diseases affect millions of people in developing countries where one of the main problems concerning the control of these diseases is diagnosis-based due to the most affected areas usually being far from laboratories having suitable infrastructure and/or being equipped with sophisticated equipment. Advances have been made during the last two decades regarding standardising and introducing techniques enabling diagnoses to be made in remote places, i.e., the loop-mediated isothermal amplification (LAMP) technique. This technique’s advantages include being able to perform it using simple equipment, diagnosis made directly in the field, low cost of each test and the technique’s high specificity. Using this technique could thus contribute toward neglected parasite infection (NPI) control and eradication programmes. This review describes the advances made to date regarding LAMP tests, as it has been found that even though several studies have been conducted concerning most NPI, information is scarce for others.

Onchocerciasis Elimination: Progress and Challenges

Onchocerciasis is a parasitic infection caused by the filarial nematode Onchocerca volvulus and transmitted through the bites of black flies of the genus Similium that breed in rivers and streams. The impact of mass treatment with ivermectin and supplemented by vector control in some countries has changed the global scene of onchocerciasis. There has been reported progress made in elimination of onchocerciasis in central and southern American countries and in some localities in Africa. The target for elimination in the Americas has been set at 2022 while for 12 countries in Africa this is expected in 2030. This review was conducted to examine the current status of onchocerciasis elimination at the global level and report on progress made. Literature searches were made through PubMed, articles in English or English abstracts, reports and any other relevant articles related to the subject. The global burden of onchocerciasis is progressively reducing and is no longer a public health problem in some regions. However, programs are challenged with a range of issues: cross-border transmission, diagnostic tools, Loa loa co-endemicity, limited workforce in entomology and maintaining enthusiasm among community drug distributors. More concerted effort using appropriate tools is required to overcome the challenges.

Status of parasitological indicators and morbidity burden of onchocerciasis after years of successive implementation of mass distribution of ivermectin in selected communities of Yeki and Asosa districts, Ethiopia

Background

Control and elimination of onchocerciasis requires regular follow-up and evaluation of community directed treatment with ivermectin (CDTi) program implementation. This research was aimed to assess the epidemiological status of onchocerciasis in disease endemic communities of Asosa and Yeki districts of Ethiopia after 5 and 15 years of successive CDTi respectively, and to evaluate the decline in infection and morbidity burden.

Methods

A community-based cross-sectional study was conducted from August 2017 to January 2018 (i.e. within 2–7 months since the last treatment) using interview, physical and parasitological examinations. Pre-CDTi epidemiological data were obtained from studies conducted prior to the launch of CDTi.

Results

A total of 3002 individuals (1567 from Asosa and 1435 from Yeki) were included. No infection was detected from Yeki. In Asosa, the prevalence of infection was 1.6%. The geometric mean intensity of infection was 0.02 mf/mg of skin snip. The prevalence rates of dermatitis, depigmentation, nodule, and atrophy in Yeki were 33(2.3%), 57(4%), 37(2.6%) and 11(0.7%), respectively. The prevalence rates of papular dermatitis, depigmentation, palpable nodule, atrophy, and blindness in Asosa were 94(6%), 38(2.4%), 30(1.9%), 28(1.8%) and 2(0.1%), respectively. Five years of CDTi had significantly reduced prevalence and intensity of infection by 91.8% (p < 0.001) and 99.7% (p < 0.001), respectively. Moreover, CDTi reduced prevalence of papular dermatitis by 95.9% (p < 0.001), palpable nodule by 90.5% (p < 0.001), and atrophy by 30% (p = 0.6) in Yeki. Similarly, CDTi reduced prevalence of papular dermatitis by 88.6% (p < 0.001), depigmentation by 90.3% (p < 0.001), atrophy by 89.5% (p < 0.001), and blindness by 90% (p < 0.001) in Asosa.

Conclusions

Fifteen years of successive CDTi had brought the infection from high to zero in Yeki. However, thorough entomological and serological data need to be generated to ascertain whether complete interruption of parasite transmission has been attained, and for considerations of an evidence-based CDTi cessation. Five years of CDTi in Asosa has significantly reduced the infection and morbidity of onchocerciasis to very low level. We, hereby, recommend biannual CDTi to continue in Asosa and its surroundings until the infection transmission is fully interrupted.

Identification of Human-Derived Attractants to Simulium damnosum Sensu Stricto in the Madi-Mid North Onchocerciasis Focus of Uganda

Human landing collections (HLCs) have been the standard method for the collection of black flies that serve as vectors for Onchocerca volvulus, the causative agent of onchocerciasis or river blindness. However, HLCs are inefficient and may expose collectors to vector-borne pathogens. The Esperanza window trap (EWT) has been shown to be a potential alternative to HLCs for the collection of Simulium damnosum, the principal vector of O. volvulus in Africa. To improve the performance of the EWT, sweat from individuals highly attractive or less attractive to S. damnosum sensu stricto was examined by gas chromatography and mass spectroscopy. Twelve compounds were identified which were solely present or present in increased amounts in the sweat of the highly attractive individuals. Two of these compounds (naphthalene and tert-hexadecyl mercaptan) were found to be attractive to S. damnosum s.s. in behavioral assays. Traps baited with these compounds outperformed those baited with the current standard bait of worn socks. Using these newly identified compounds as baits will make the EWT more efficient in collecting vector black flies and may enhance the potential utility of the EWT as a local vector control measure.

In Silico Design and Validation of OvMANE1, a Chimeric Antigen for Human Onchocerciasis Diagnosis

The public health goal of onchocerciasis in Africa has advanced from control to elimination. In this light, accurate diagnosis is necessary to determine treatment endpoints and confirm elimination, as well as to conduct surveillance for the identification of any possible recrudescence of the disease. Currently, the monitoring of onchocerciasis elimination relies on the Ov-16 test. However, this test is unable to discriminate between past and active infections. Furthermore, about 15-25% of infected persons are reported to be negative for the Ov-16 test, giving a misleading sense of security to false-negative individuals who might continue to serve as reservoirs for infections. Therefore, we opted to design and validate a more sensitive and specific chimeric antigen (OvMANE1) for onchocerciasis diagnosis, using previously reported immunodominant peptides of O. volvulus, the parasite responsible for the disease. In silico analysis of OvMANE1 predicted it to be more antigenic than its individual peptides. We observed that OvMANE1 reacts specifically and differentially with sera from O. volvulus infected and non-infected individuals, as well as with sera from communities of different levels of endemicity. Moreover, we found that total IgG, unlike IgG4 subclass, positively responded to OvMANE1, strongly suggesting its complementarity to the Ov-16 diagnostic tool, which detects Ov-16 IgG4 antibodies. Overall, OvMANE1 exhibited the potential to be utilized in the development of specific diagnostic tools-based on both antibody capture and antigen capture reactions-which are indispensable to monitor the progress of onchocerciasis elimination programs.