A controlled, parallel, cluster-randomized trial of community-wide screening and treatment of asymptomatic carriers of Plasmodium falciparum in Burkina Faso

Abstract

BackgroundIn malaria-endemic countries, large proportions of infected individuals are asymptomatic, constituting a reservoir of parasites for infection of newly hatched mosquitoes. This study evaluated the impact of screening and treatment of asymptomatic carriers of Plasmodium falciparum.MethodsEighteen villages were randomized (1:1) to study arms and inhabitants participated in four community screening campaigns: three before the rainy season ~1 month apart, and the fourth after the rains at ~12 months. On day 1 of campaigns 1–3, asymptomatic carriers in the intervention arm were identified by rapid diagnostic test and treated with artemether-lumefantrine. Outcomes were symptomatic malaria with parasite density >5,000/μL per person-year in children < 5 years and change in haemoglobin between days 1 and 28 of campaign 1.ResultsAt 12 months, the number of symptomatic malaria episodes with a parasite density >5,000/μL per person-year in children < 5 years was not significantly different between arms (1.69 vs 1.60, p = 0.3482). Mean haemoglobin change in asymptomatic carriers during campaign 1 was greater in the intervention vs control arm (+0.53 g/dL vs -0.21 g/dL, p < 0.0001). ANCOVA demonstrated that mean asymptomatic carriage at the cluster level was lower in the intervention vs control arm at day 1 of campaigns 2 (5.0% vs 34.9%, p < 0.0001) and 3 (3.5% vs 31.5%, p < 0.0001), but showed only a small difference at day 1 of campaign 4 (34.6% vs 37.6%, p = 0.2982). Mean gametocyte carriage was lower in the intervention vs control arm at day 1 of campaigns 2 and 3 (0.7% vs 5.4%, p < 0.0001; 0.5% vs 5.8%, p < 0.0001), but was similar at day 1 of campaign 4 (4.9% vs 5.1%, p = 0.7208).ConclusionsSystematic screening and treatment of asymptomatic carriers at the community level did not reduce clinical malaria incidence in the subsequent transmission season, indicating greater levels of parasite clearance are required to achieve a sustained impact in this setting.

Assessing the impact of next-generation rapid diagnostic tests on Plasmodium falciparum malaria elimination strategies

“…Large areas of southern and eastern Africa have EIR values below 4, indicating that repeated MSAT programmes with a high-sensitivity diagnostic test of the order of 2 parasites per microlitre could be considered as an intervention in these areas 43 . However, the EIR in Burkina Faso is much higher than 4, suggesting that MSAT would not be effective even with a highly sensitive diagnostic test (as confirmed in a recent trial 17,18 ). Equally, using a higher sensitivity diagnostic could reduce the number of treatment rounds required to interrupt transmission, thus reducing the operational and financial requirements and potentially increasing the community acceptance of the intervention.…”

“…Two recent MSAT trials, which used RDT screening to identify infections, failed to lead to a sustained reduction in malaria parasite prevalence or disease incidence 17,18 . It has been suggested that this could be at least partly due to ongoing transmission from low-density infections that were undetectable by the RDT or by microscopy.…”

Elevated prevalence of malnutrition and malaria among school-aged children and adolescents in war-ravaged South Sudan

“…18 On the other hand, a recent trial in Burkina Faso indicated no impact of IST on community-wide malaria transmission. 27 Further studies are ongoing to test whether school children can be used to detect and monitor malaria "hotpots" within a community, where localized transmission and re-infection rates are high. This could, in turn, trigger intensive hotspot-focused community interventions to interrupt malaria transmission.…”

Estimation of the Overall Treatment Effect in the Presence of Interference in Cluster-Randomized Trials of Infectious Disease Prevention

“…Hence in this trial, information is collected about the number of sexual contacts that occur with residents of villages outside that of the index subject. Regardless of distance between clusters, if a fraction of the exposures among subjects in the treatment clusters come from outside the cluster the estimate of the randomized treatment effect of an infectious disease prevention strategy will be attenuated compared to what it would have been had the treatment been implemented throughout the population of interest (Tiono et al 2013;Wang et al 2014).…”