Modelling the impact of COVID-19-related control programme interruptions on progress towards the WHO 2030 target for soil-transmitted helminths

Abstract

Background On the 1st of April 2020, the World Health Organization (WHO) recommended an interruption of all neglected tropical disease control programmes, including soil-transmitted helminths (STH), in response to the COVID-19 pandemic. This paper investigates the impact of this disruption on the achieved progress towards the WHO 2030 target for STH. Methods We used two stochastic individual-based models to simulate the impact of missing one or more preventive chemotherapy (PC) rounds in different endemicity settings. We also investigate the extent to which the impact can be lessened by mitigation strategies, such as semi-annual or community-wide PC. Results Both models show that even without a mitigation strategy, control programmes will catch up by 2030. The catch-up time is limited to a maximum of 4.5 years after the interruption. Mitigations strategies may reduce this catch-up time by up to two years and can even increase the probability of achieving the 2030 target. Conclusions Though a PC interruption will only temporarily impact the progress towards the WHO 2030 target, programmes are encouraged to restart as soon as possible to minimise the impact on morbidity. The implementation of suitable mitigation strategies can turn the interruption into an opportunity to accelerate the progress toward reaching the target.

Evaluating the potential impact of interruptions to neglected tropical disease programmes due to COVID-19

“…For visceral leishmaniasis in the Indian subcontinent, as well as trachoma and schistosomiasis, interruptions to programmes will therefore undermine the gains made over many years and considerably delay achievement of the 2030 targets. For soil-transmitted helminths 20 there are a range of resurgence rates, approximately in proportion to the inverse of the worm’s lifespan. 21…”

How modelling can help steer the course set by the World Health Organization 2021-2030 roadmap on neglected tropical diseases

“…This has added clout to the call for modelling in the policy arena as well as setting a high bar of best practice for the wider modelling community. Having now gained significant traction, the use of modelling in NTD policy has contributed to new intervention tools 22 , vector control strategies [23][24][25][26] , shaped policy responding to COVID-19-related programme disruptions [27][28][29][30][31][32][33][34][35] and has aided in the development of WHO guidelines 36,37 . For this positive relationship to continue, it is imperative to invest in a mutual understanding through ongoing conversation between policy-makers and modellers, to determine what kind of questions are the "right" questions, how to interpret uncertainty and what the models can and cannot be used for.…”

Impact of Key Assumptions About the Population Biology of Soil-Transmitted Helminths on the Sustainable Control of Morbidity

“…Locations with the same pretreatment prevalence of STH infections may have different levels of worm aggregation and may therefore require different optimal treatment strategies. In areas with a high aggregation of worms among hosts, achieving the morbidity target may require more time or a higher treatment frequency [ 12 ]. Simulation models with the same baseline prevalence but different aggregation levels show that in moderate-prevalence settings with a high aggregation of worms among hosts semi-annual PC treatment may be required to reach the morbidity target by 2030, whereas settings with the same baseline prevalence and lower aggregation can reach the target with annual PC treatment ( Figure 1a ).…”