What does the COVID-19 pandemic mean for the next decade of onchocerciasis control and elimination?

BACKGROUND

Mass drug administration (MDA) of ivermectin for onchocerciasis has been disrupted by the coronavirus disease 2019 (COVID-19) pandemic. Mathematical modelling can help predict how missed/delayed MDA will affect short-term epidemiological trends and elimination prospects by 2030.

METHODS

Two onchocerciasis transmission models (EPIONCHO-IBM and ONCHOSIM) are used to simulate microfilarial prevalence trends, elimination probabilities and age profiles of Onchocerca volvulus microfilarial prevalence and intensity for different treatment histories and transmission settings, assuming no interruption, a 1-y (2020) interruption or a 2-y (2020-2021) interruption. Biannual MDA or increased coverage upon MDA resumption are investigated as remedial strategies.

RESULTS

Programmes with shorter MDA histories and settings with high pre-intervention endemicity will be the most affected. Biannual MDA is more effective than increasing coverage for mitigating COVID-19's impact on MDA. Programmes that had already switched to biannual MDA should be minimally affected. In high-transmission settings with short treatment history, a 2-y interruption could lead to increased microfilarial load in children (EPIONCHO-IBM) and adults (ONCHOSIM).

CONCLUSIONS

Programmes with shorter (annual MDA) treatment histories should be prioritised for remedial biannual MDA. Increases in microfilarial load could have short- and long-term morbidity and mortality repercussions. These results can guide decision-making to mitigate the impact of COVID-19 on onchocerciasis elimination.

Valuing the Unpaid Contribution of Community Health Volunteers to Mass Drug Administration Programs

Community health volunteers (CHVs) are being used within a growing number of healthcare interventions, and they have become a cornerstone for the delivery of mass drug administration within many neglected tropical disease control programs. However, a greater understanding of the methods used to value the unpaid time CHVs contribute to healthcare programs is needed. We outline the two main approaches used to value CHVs’ unpaid time (the opportunity cost and the replacement cost approaches). We found that for mass drug administration programs the estimates of the economic costs relating to the CHVs’ unpaid time can be significant, with the averages of the different studies varying between US$0.05 and $0.16 per treatment. We estimated that the time donated by CHVs’ to the African Programme for Onchocerciasis Control alone would be valued between US$60 and $90 million. There is a need for greater transparency and consistency in the methods used to value CHVs’ unpaid time.

Transitioning from river blindness control to elimination: steps toward stopping treatment

The transition from onchocerciasis control to elimination requires country programmes to rethink their approach to a variety of activities as they move from addressing morbidity to addressing transmission of the parasite. Although the 2016 WHO guidelines provide extensive recommendations, it was beyond the scope of the document to provide guidance on all aspects of the transition. This paper will discuss some of the important issues that programmes are grappling with as they transition to elimination and provide some potential approaches that programmes can use to address them. Although there are some data to support some aspects of the suggested approaches, operational research will be needed to generate data to support these approaches further and to determine how programmes could best tailor them to their own unique epidemiological challenges. Good communication between the national programmes and the broader global programme will facilitate the clear articulation of programmatic challenges and the development of the evidence to support programme decision-making.

Elimination of African onchocerciasis: modeling the impact of increasing the frequency of ivermectin mass treatment

The African Programme for Onchocerciasis Control (APOC) is currently shifting its focus from morbidity control to elimination of infection. To enhance the likelihood of elimination and speed up its achievement, programs may consider to increase the frequency of ivermectin mass treatment from annual to 6-monthly or even higher. In a computer simulation study, we examined the potential impact of increasing the mass treatment frequency for different settings. With the ONCHOSIM model, we simulated 92,610 scenarios pertaining to different assumptions about transmission conditions, history of mass treatment, the future mass treatment strategy, and ivermectin efficacy. Simulation results were used to determine the minimum remaining program duration and number of treatment rounds required to achieve 99% probability of elimination. Doubling the frequency of treatment from yearly to 6-monthly or 3-monthly was predicted to reduce remaining program duration by about 40% or 60%, respectively. These reductions come at a cost of additional treatment rounds, especially in case of 3-monthly mass treatment. Also, aforementioned reductions are highly dependent on maintained coverage, and could be completely nullified if coverage of mass treatment were to fall in the future. In low coverage settings, increasing treatment coverage is almost just as effective as increasing treatment frequency. We conclude that 6-monthly mass treatment may only be worth the effort in situations where annual treatment is expected to take a long time to achieve elimination in spite of good treatment coverage, e.g. because of unfavorable transmission conditions or because mass treatment started recently.

Elimination of onchocerciasis from Africa: possible?

Human onchocerciasis, a parasitic disease found in 28 African countries, six Latin American countries and Yemen, causes blindness and severe dermatological problems. In 1987, efforts to control this infection shifted from vector approaches to include the mass distribution of ivermectin - a drug donated by Merck & Co. for disease control in Africa and for disease elimination in the Americas. Currently, almost 25 years later, with the Americas being highly successful and now approaching elimination, new evidence points towards the possibility of successful elimination in Africa. We suggest several major changes in the programmatic approach that through focused goal-directed effort could achieve global elimination of onchocerciasis by 2025.

Ivermectin and onchocerciasis: is it all solved?

The donation of ivermectin by Merck and Co. Inc. has led to one of the most effective private-public partnerships controlling a disease of major public health importance particularly in Africa. The up scaling of ivermectin distribution during the last 15 years has been remarkable with almost 40 million people treated in 2003, many already on their regular annual dose. The tools that have been developed particularly by the APOC programme have been instrumental in this increase. However, ivermectin is a microfilaricide and does not kill the adult worms. Distribution will be needed for at least 25 years and latest estimates indicate that 90 million people need annual treatment if onchocerciasis is to be eliminated as a public health problem. In spite of this incredible progress it is difficult to see how the programme will be sustained, especially after the closure of APOC in 2010. A macrofilaricide destroying adult worms and safe for mass distribution would solve the problem of onchocerciasis.

The effect of 5 years of annual treatment with ivermectin (Mectizan) on the prevalence and morbidity of onchocerciasis in the village of Gami in the Central African Republic

To assess the impact of 5 years of annual community treatment with ivermectin (Mectizan) on the prevalence of onchocerciasis and onchocerciasis-associated morbidity, data collected, before and after such treatment, in the village of Gami, in a hyper-endemic area of the Central African Republic, were analysed. Skin snips from all the villagers treated in 1990 and/or 1995 were used to assess the prevalence and intensity of infection with Onchocerca volvulus. Ocular and dermatological morbidity was assessed by ophthalmological and clinical examinations of the same subjects. Following the five annual treatments, there was a reduction in the prevalence of infection and a dramatic decrease in the microfilarial load of the community. The prevalences of pruritus, onchocercal nodules and impaired vision were all significantly reduced. The results emphasise the long-term benefits of the mass-treatment programmes, particularly for children aged <10 years.

A method to determine the coverage of ivermectin distribution in onchocerciasis-control programmes

Onchocerciasis is a human filarial infection responsible for an estimated 750,000 blind and severely visually disabled people. In some African countries, this disease represents the main cause of blindness, with considerable socio-economic impact on the affected communities. Since the introduction of ivermectin as a microfilaricidal agent, there is hope that visual loss from onchocerciasis can be eliminated through community-based ivermectin-distribution programmes. The African Programme for Onchocerciasis Control (APOC) has now been initiated, by the World Health Organization and World Bank, to distribute ivermectin in 19 African countries where onchocerciasis is endemic. Estimates of ivermectin coverage in distribution programmes for onchocerciasis control have so far been based on the number of treatments given, in any one year, to a target population. There is a need for a standardized method to evaluate, measure and monitor coverage over time. In April 1996, a cluster random-sampling method was used to calculate coverage with ivermectin in an urban population of 30,000 people in the Central African Republic. The method was adapted from that used to determine coverage by the WHO Expanded Programme on Immunization. It proved to be inexpensive and easy to perform, requiring only local equipment and personnel. The method used and results obtained in Bossangoa and the potential use of the technique in other distribution programmes are discussed.

Low-temperature synthesis of zintl compounds with a single-source molecular precursor

Thermolysis of the heterobimetallic phosphinidene complex [Sb(PCy)3]2- Li6.6HNMe2 (Cy = C6H11) at 303 to 313 kelvin gives Zintl compounds containing (Sb7)3- anions. The complex thus constitutes a stable molecular single-source precursor to Zintl compounds and provides a potential low-temperature route to photoactive alkali metal antimonates. The new chemical reaction involved, which is driven thermodynamically by the formation of P-P bonds, has implications in the low-temperature synthesis of other technologically important materials (such as gallium arsenide).

Mectizan delivery systems and cost recovery in the Central African Republic

The Central African Republic (CAR) has a serious onchocerciasis problem. The disease is endemic in three quarters of the country and there is considerable onchocercal blindness in the north-west. The low population density and extreme poverty (the CAR being one of the 20 poorest countries in the world) combine to make mass treatment with Mectizan (ivermectin, MSD) a challenge. Although planned, primary health care (PHC) is not widely developed in the country. Mectizan distribution was carried out in 1993-1994 by mobile teams in order to address the most urgent need, particularly in the north-west. Since then, the strategy has been one of community involvement, using village health workers, chosen by their own communities, to do the treatment. The system has been a stimulus to the development of PHC in some areas, as the co-ordinators of the Mectizan programme are often the only health personnel to visit every village. The long distances between health centres, with a mean of 45 km, are likely to be an obstacle to the population collecting their own Mectizan, within the self-treatment system otherwise in place. Operational research is planned to examine ways in which the population can contribute to cost recovery without there being a reduction in treatment coverage.

Therapeutic trial of four amoebicide regimes in rural Zaire

A prospective comparative trial of four amoebicide regimes was carried out with protozoological control using 300 patients presenting with symptomatic intestinal amoebiasis at a tropical rural hospital during a five month period. 195 (76.2%) of 256 treated supplied three follow-up stools. Of those treated with Metronidazole and Oxytetracycline 10.9 per cent continued to excrete Entamoeba histolytica while with Di-iodohydroxyquinoline and Oxytetracycline the figure was 25.5 per cent falling to 20.0 per cent when Dehydroemetine was added and with Clioquinol and Oxytetracycline 27.5 per cent continued to excrete Entamoeba histolytica. These figures with the absolute numbers of patients involved do not show any one of the regimes used to be significantly more effective than the others in unclassified symptomatic intestinal amoebiasis. We conclude therefore that in the rural situation the cheapest regime should be preferred as the standard one, namely Clioquinol and Oxytetracycline. However, in view of the reported serious side-effects of Clioquinol, Di-iodomydroxyquinoline and Oxytetracycline could be considered as the second cheapest and with slightly better results.

The effect of postoperative peritoneal lavage on survival, peritoneal wound healing and adhesion formation following fecal peritonitis: an experimental study in the rat

The effect of postoperative peritoneal lavage on survival, peritoneal wound healing and adhesion formation has been studied in rats both with and without fecal peritonitis. Peritoneal lavage with both Hartmann's solution and noxytiolin through an indwelling peritoneal cannula resulted in a delay in peritoneal wound healing in the absence of fecal peritonitis. There was also an increase in the incidence of adhesions. Induction of a fecal peritonitis followed by operation 2½–3 hours later resulted in 100 per cent mortality within 24 hours. This mortality was reduced by 66 per cent following peritoneal lavage with Hartmann's solution alone, although this resulted in a delay in peritoneal wound healing. Peritoneal lavage with noxytiolin did not reduce the mortality rate.