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Tackling the hidden pandemic: anticipating and preventing mosquito-borne diseases

Written by Vikrant Panwar

Image credit:Arne Hoel / World Bank Image license:CC BY-NC-ND 2.0

‘Anticipatory action’ is the new buzzword for humanitarian and development agencies working to avert climate impacts and minimise loss and damage, and may well become a key strategy for dealing with future projected climate extremes. Calls are growing for finance to be allocated before disasters occur – not during a crisis. But there’s been little mention in these discussions of mosquito-borne diseases, which are amongst the biggest killers in low-income countries. Improvements in monitoring and understanding of how these vector-borne diseases spread make anticipatory action to reduce the impacts entirely possible. So why isn’t this on the agenda of anticipatory action proponents?

Risks of a bite

Mosquitoes kill more than one million people per year. They transmit a pathogen that causes diseases like malaria, dengue and yellow fever. The public health agencies that deal with these diseases also now face unprecedented pressures due to COVID-19 cases, particularly in Africa. According to the World Malaria Report 2020, malaria results in more than 400,000 deaths annually, with 94% in Africa alone. Similarly, almost 4 billion people in 129 countries are at risk of contracting dengue which results in an estimated 96 million symptomatic cases and 40,000 deaths every year.

Mosquito-borne diseases have significant economic costs. These are estimated to be at least US$ 12 billion per year, with households losing an estimated 25% of their income in out-of-pocket expenditure on malaria treatment and related travel and diagnosis. Despite these staggering figures, these ‘silent killers’ have failed to grab the headlines.

But this may be about to change. Emerging evidence suggests that climate change is fuelling the risks of mosquito-borne diseases worldwide. With so much focus at COP26 on ‘anticipatory action’ for extreme weather, it is high time the fight against mosquito-borne diseases is recalibrated and public health systems are geared up to better anticipate, prevent and contain diseases.

Global fight against mosquito-borne diseases

Efforts to reduce mosquito-borne diseases have stepped up, with the World Health Organization (WHO) at the forefront. This resulted in a 60% decline in global malaria mortality between 2000-2019, and 21 countries eradicating the disease. In 2001, African governments committed to spending 15% of their budgets on health systems (although few have actually achieved that target), and in 2002, a US$4 billion Global Fund was set up to tackle HIV, TB and malaria. Promotion of insecticide-treated mosquito nets (ITNs) has been key to reducing malaria outbreaks. Most recently, the WHO’s recommendation of a malaria vaccine among children is seen as a ground-breaking development that could prove vital in achieving the target of a 90% reduction in the malaria burden by 2030.

But progress has plateaued in recent years and in parallel, dengue is becoming the most common and the fastest spreading mosquito-borne disease worldwide.

The fight against mosquito-borne diseases is at a “crossroads” and it must be reignited with much greater emphasis on prevention and surveillance, leading to complete elimination.

Can anticipatory action help curb mosquito-borne diseases?

Anticipatory action, taken after there is a forecast but before a disaster occurs (or a crisis becomes acute), has proven to be beneficial in mitigating the adverse effects of disasters. Critical actions have involved providing livestock fodder to pastoralists before a drought, or cash to households before flooding occurs to pay for evacuations and food that will be needed. But perhaps the most important ‘action’ is the provision of information and advice, so people can make better decisions themselves to prepare.

Anticipatory action for mosquito-borne diseases is not a widespread practice in Africa, but the MosquitoNET project in Tanzania is trying to address this by developing community-based approaches to vector surveillance, training individuals to become ‘community entomologists’ and using mobile phones to record and share data. Researchers hope to inform the development of early warning systems for malaria and dengue in Tanzania. These can be used to trigger early measures to control the outbreak – through vaccination programmes, vector control, preventive chemotherapies and effective case management (early diagnosis and treatment).

But anticipatory action is not a ‘silver bullet’ for reducing mosquito-borne diseases or other disaster impacts. Critically, it needs to be complemented with long-term planning and system-wide changes to reduce the risks – including improved water, sanitation and hygiene (WASH) systems, and immunisation programmes. In essence, anticipatory action is not a new undertaking, but it offers a novel and more robust perspective of approaching a crisis, moving from only a relief-focussed approach to a cohesive one with shared responsibilities between communities, governments, and humanitarian and development partners.

What’s next?

Despite continuous efforts, mosquito-borne diseases still pose serious public health risks. Climate change is expected to make these diseases more severe, with rising temperatures pushing mosquitos to unexposed areas. A powerful and collaborative global effort is needed to eliminate malaria and other mosquito-borne diseases from Africa, and eventually from the face of the earth.

Anticipatory action for mosquito-borne diseases means ensuring effective treatment is pre-arranged and delivered to at-risk populations. This will require close collaboration between different stakeholders for prevention and surveillance, as well as adequate financing. Anticipatory action is already a key feature of efforts to prevent malaria and dengue outbreaks, but needs more attention. Equally, other actors interested in anticipatory action have a lot to learn from the efforts of public health authorities and the WHO in surveillance and control of mosquito-borne diseases.