To date, the World Health Organisation has certified 38 countries and territories malaria-free. In southern Africa, eight countries – including South Africa and Namibia – have made the elimination of malaria a policy goal.
In recent years, however, progress towards eliminating transmission has slowed in many regions including Africa, highlighting the need for new approaches. Where malaria cases have been reduced to low levels, transmission still occurs due a reservoir of chronic, low density infections in people without symptoms. This means that these infections are largely undetectable through standard surveillance approaches.
This trial, conducted in Northern Namibia, demonstrates how malaria incidence can be reduced by up to 75% in settings where malaria transmission is mostly low, but persistent, and plagued by sporadic outbreaks of higher numbers of malaria cases. Principal Investigator, Professor Immo Kleinschmidt noted:
'The reduction in cases was achieved using existing tools, namely anti-malarial drugs and insecticides, but deploying these in a ‘smart’ way, i.e. in close proximity of newly reported cases.'
During the trial, neighbours of any new malaria case were offered a standard dose of the anti-malarial Coartem® (without first testing whether they carried parasites), and had the interior walls of their houses sprayed with insecticide, regardless of whether their houses had been previously sprayed in the annual spray round routinely carried out in such areas. Communities were randomised to receive either one, both or none of these interventions. Both interventions were shown to be safe and highly effective, alone, and together
On the last mile to achieving elimination, malaria transmission and appearance of asymptomatic and clinical infections become increasingly focal. Targeted reactive approaches, such as reactive case detection (RACD), are likely to form efficient interventions to eliminate infections and prevent onward transmission.
In a low Plasmodium falciparum endemic area of north-eastern Namibia, Kleinschmidt and colleagues at LSHTM (in collaboration with Scientists at the University of California, San Francisco; University of the Witwatersrand in South Africa; the University of Namibia; Namibia Ministry of Health and Social Services; and the University of Texas, Southwestern), applied an innovative approach to test two such interventions: reactive focal mass drug administration (rfMDA) implemented as presumptive treatment with artemether-lumefantrine (AL) and reactive focal vector control (RAVC) by indoor residual spraying of the insecticide pirimiphos-methyl. The cluster-randomized trial was conducted in 56 census unit clusters. It applied a two-by-two factorial design that allowed for a comparison of rfMDA against RACD (rapid diagnostic testing and treatment with AL), RAVC against no RAVC, and a combination of rfMDA+RAVC against RACD.
Because the mosquitoes that carry the malaria parasite are still present, these infections may seed further infections in their immediate neighbourhood, potentially leading to outbreaks of malaria cases. To prevent such outbreaks from leading to wider epidemics, effective focal responses that target high-risk populations, such as those assessed in the Namibian study, need to be mobilised.
While additional studies will help determine the optimal scenarios in which these approaches could be implemented, the Namibian study suggests that reactive focal mass drug administration and reactive focal vector control can be applied in other countries that (i) have Plasmodium falciparum parasite-carrying mosquitoes (ii) are close to eliminating transmission and (iii) have good case reporting systems.
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