RHOST-cRCT, Reactive Household-based Self-administered Treatment Against Residual Malaria Transmission (RHOST)

Achieving malaria elimination presents a challenge because of important gaps in the knowledge about the strategies and tools needed achieve this. While malaria control measures aim to reduce morbidity and mortality in vulnerable populations, interventions to reduce transmission are designed to interrupt transmission of malaria parasites from humans, especially asymptomatic parasite carriers \[1\], to mosquitoes.

The importance of asymptomatic infections in transmission has grown with the awareness that the majority of the human reservoir of infection are asymptomatic carriers \[2\] and these are quite difficult to target \[3\]. Previous malaria elimination campaigns have applied a strategy of mass drug administration: extensive treatment of entire populations, irrespective of their infection status, in one or multiple rounds \[4\]. Although transmission was interrupted in some cases, albeit temporarily \[5\], there is a reluctance to apply this method because the evidence of its impact has been mixed. A Cochrane systematic review of MDAs showed that long term reductions were not possible within the current concept and highlighted the need for studies in low- and moderate-transmission settings and studies that could address potential barriers for community uptake, and contribution to the development of drug resistance \[6\].

More conservative approaches involving screening for infection with a rapid malaria diagnostic test (RDT) and treating only positive individuals; mass screening and treatment, did not have a significant impact on the malaria incidence \[7\], largely due to low test's sensitivity that would miss a large proportion of infected individuals with low parasite densities. Implementing reactive screening on a programmatic scale puts significant pressure on the health system \[8\] and available field-based screening tests lack the required sensitivity for low-density parasitaemia seen with asymptomatic infections \[9\]. More importantly, understanding the local context and adapting intervention strategies may help improve coverage and participation by recipient communities \[10\].

This study investigates a novel approach to reducing residual malaria transmission that combines the elements of reactive treatment of household contacts of a clinical case reporting at a health facility with the active involvement of both patients and their households. The approach to implementation will be developed through formative research that identifies the optimum means of community engagement that will result in the best possible compliance and adherence to the treatment in the household.