Malaria elimination on Hainan Island despite climate change

Abstract

Background Rigorous assessment of the effect of malaria control strategies on local malaria dynamics is a complex but vital step in informing future strategies to eliminate malaria. However, the interactions between climate forcing, mass drug administration, mosquito control and their effects on the incidence of malaria remain unclear. Methods Here, we analyze the effects of interventions on the transmission dynamics of malaria (Plasmodium vivax and Plasmodium falciparum) on Hainan Island, China, controlling for environmental factors. Mathematical models were fitted to epidemiological data, including confirmed cases and population-wide blood examinations, collected between 1995 and 2010, a period when malaria control interventions were rolled out with positive outcomes. Results Prior to the massive scale-up of interventions, malaria incidence shows both interannual variability and seasonality, as well as a strong correlation with climatic patterns linked to the El Nino Southern Oscillation. Based on our mechanistic model, we find that the reduction in malaria is likely due to the large scale rollout of insecticide-treated bed nets, which reduce the infections of P. vivax and P. falciparum malaria by 93.4% and 35.5%, respectively. Mass drug administration has a greater contribution in the control of P. falciparum (54.9%) than P. vivax (5.3%). In a comparison of interventions, indoor residual spraying makes a relatively minor contribution to malaria control (1.3%–9.6%). Conclusions Although malaria transmission on Hainan Island has been exacerbated by El Nino Southern Oscillation, control methods have eliminated both P. falciparum and P. vivax malaria from this part of China.

Climate change and parasitic risk to the blood supply

“…Factors driving malaria transmission in urban areas may differ from those in rural areas (Table S1). The impact of climate change on malaria may also be limited by public health control activities 39 . As seen in Hainan China (Table S1), predicting the future malaria burden in a region due to climate change is complicated and will vary depending on elevation, temperature, humidity, and human behavior changes as well as planned public health interventions 38,39 …”

“…The impact of climate change on malaria may also be limited by public health control activities. 39 As seen in Hainan China (Table S1), predicting the future malaria burden in a region due to climate change is complicated and will vary depending on elevation, temperature, humidity, and human behavior changes as well as planned public health interventions. 38,39 Global warming is predicted in models to increase the range of triatomines north and south over the next 30 years (Table S1).…”

Quantifying the impact of interventions againstPlasmodium vivaxmalaria: a model for country-specific use

“…Firstly, the chosen representation of treatment delays assumes that host infectiousness to mosquitoes is constant over time, which is an important simplification in regard to the complex life cycle of the malaria parasites [Gaspoz and al., in prep] and the relaxation of this assumption will be the object of future work. In addition, delays in access to treatment were represented with exponential durations via the ODE formalism and not fixed durations as would have been the case with delay differential equations [Kim et al, 2021, Tian et al, 2022]. Nonetheless, the chosen formalism of the model presents some similarities with a model based on delayed-differential equations, as illustrated in Appendix A for a simpler model with perfect radical cure.…”

“…Various P. vivax models have recently been developed (e.g. [White et al, 2018, Kim et al, 2021, Tian et al, 2022]), but they are not always readily operationalized for being used routinely at country level, either because they don’t include all the above-mentioned interventions, or because their calibration to routine data is not straightforward to implement.…”

The Phylodynamic and Spread of the Invasive Asian Malaria Vectors, Anopheles stephensi, in Sudan

“…stephensi [35]. More importantly, local and international studies have reported that climate change is a major driver for the increase in the transmission of malaria and other vector-borne diseases [36,37]. As a sub-Saharan country where most of the environment throughout the country constitutes deserts and semi-deserts, the survival of diseases vectors is mainly limited to microenvironments surrounding water bodies with grassy covers such as banks of rivers [3].…”