Could 2016 be a bad year for the malaria parasite in Africa?

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A new study led by the University of Oxford suggests that more insecticide-treated nets (ITNs) and improved efficiency in net delivery are needed to achieve universal coverage and make serious headway on the path to elimination in 2016.

The paper, to be published in the journal eLife, suggests that malaria net coverage currently remains well below the 100% universal coverage target. Estimates for the number of nets needed to achieve 100% coverage are also too low, as a result of diminishing returns caused by inefficiencies in net delivery.

A second paper, to be published on the same day in eLife, evaluates progress in Swaziland towards becoming sub-Saharan Africa’s first malaria-free country.

“Insecticide-treated nets, which comprise conventional and long-lasting insecticidal nets (LLINs), are the single most widely used intervention for malaria control in Africa, but coverage remains inadequate,” says Samir Bhatt, lead author of the malaria net coverage study.

“Sub-Saharan African countries at risk of malaria have calculated that 920 million ITNs would be needed across the continent to achieve national coverage targets between 2014 and 2017, but this figure does not take system inefficiencies into account.”

By gathering data on ITN distribution, delivery and coverage, the team has provided new insights into two key inefficiencies, namely net loss and over-allocation.

They estimate that rates of ITN loss from households are more rapid than previously thought, with on average 50% lost after 23 months. An average of 21% of ITNs were over-allocated in 2013 and this has worsened over time as overall net provision has increased.

“Over-allocating nets becomes a major barrier to achieving universal coverage when ITN provision is high, because most new incoming nets simply lead to surpluses in many households while shortfalls remain elsewhere,” Bhatt explains.

The study suggests that the current estimation of 920 million additional nets needed to achieve universal coverage between 2014 and 2017 would in reality yield diminishing returns and a lower-than-expected level of coverage, with only 77% of the population able to access them.

With minimal over-allocation and longer ITN retention times, however, the 920 million nets could approach the goal of universal population access. Improving inefficiencies must therefore be considered in line with providing larger volumes of nets if higher coverage is to be achieved in 2016.

Similarly, the second study, led by Indiana University, suggests that countries with malaria prevention tools must determine how best to deploy them to achieve and sustain elimination, given constrained resources.

This challenge is currently faced by Swaziland, which is on the verge of elimination and, if successful, would provide valuable lessons from its national experience for the rest of the continent.

Using routine national surveillance data from Swaziland, the team estimated individual reproductive numbers and combined fine-grain maps of these numbers with local malaria importation rates to show ‘malariogenic potential.’ This refers to the interaction and effects of receptivity and vulnerability to malaria and is a first in disease elimination.

“Such measures of transmission risk, based on individual people, provide meaningful metrics for planning responses and prioritising areas where interventions will contribute most to malaria elimination,” says lead author Robert Reiner.

“Predictions generated by the approach will also be useful as a baseline for in-development genetic testing and molecular typing models, and can help Swaziland reassess its needs and remain malaria-free as surrounding countries make further progress in 2016.”