Modelling the cost-effectiveness of mass screening and treatment for reducing Plasmodium falciparum malaria burden

Abstract

BackgroundPast experience and modelling suggest that, in most cases, mass treatment strategies are not likely to succeed in interrupting Plasmodium falciparum malaria transmission. However, this does not preclude their use to reduce disease burden. Mass screening and treatment (MSAT) is preferred to mass drug administration (MDA), as the latter involves massive over-use of drugs. This paper reports simulations of the incremental cost-effectiveness of well-conducted MSAT campaigns as a strategy for P. falciparum malaria disease-burden reduction in settings with varying receptivity (ability of the combined vector population in a setting to transmit disease) and access to case management.MethodsMSAT incremental cost-effectiveness ratios (ICERs) were estimated in different sub-Saharan African settings using simulation models of the dynamics of malaria and a literature-based MSAT cost estimate. Imported infections were simulated at a rate of two per 1,000 population per annum. These estimates were compared to the ICERs of scaling up case management or insecticide-treated net (ITN) coverage in each baseline health system, in the absence of MSAT.ResultsMSAT averted most episodes, and resulted in the lowest ICERs, in settings with a moderate level of disease burden. At a low pre-intervention entomological inoculation rate (EIR) of two infectious bites per adult per annum (IBPAPA) MSAT was never more cost-effective than scaling up ITNs or case management coverage. However, at pre-intervention entomological inoculation rates (EIRs) of 20 and 50 IBPAPA and ITN coverage levels of 40 or 60%, respectively, the ICER of MSAT was similar to that of scaling up ITN coverage further.ConclusionsIn all the transmission settings considered, achieving a minimal level of ITN coverage is a “best buy”. At low transmission, MSAT probably is not worth considering. Instead, MSAT may be suitable at medium to high levels of transmission and at moderate ITN coverage. If undertaken as a burden-reducing intervention, MSAT should be continued indefinitely and should complement, not replace, case management and vector control interventions.

Monitoring, characterization and control of chronic, symptomatic malaria infections in rural Zambia through monthly household visits by paid community health workers

“…Given the imperfect detection sensitivity of RDTs [93,94] and the rapid rates of re-infection that can be expected in a setting with such a high EIR [30,95-98], it is unsurprising that at least monthly screening and treatment is required to achieve dramatic reductions of malaria infection burden (Figure 4B), associated symptoms (Figure 7), and presumably transmission [27,99,100], even assuming these two figures reflect genuine impact rather than mere association. However, it is certainly encouraging that the apparent impacts among residents consenting to such frequent testing and treatment, which these associations suggest, compare very well with simulations and field data from annual mass screen and treat programmes [40], and even simulations and field observations of year-long mass drug administration programmes with treatment cycles of only four or even two weeks [19]. It may also be encouraging that, despite their known limited sensitivity, RDTs appear to be sensitive enough to detect persistent malaria infections if each individual is tested often enough (Figure 4B) so that the frequent sporadic surges of detectable parasitaemia characteristic of P. falciparum are captured [101,102].…”

A second chance to tackle African malaria vector mosquitoes that avoid houses and don't take drugs

“…2,54,55 Some notable successes have been reported from areas of modest endemicity [42][43][44][45] where theory suggests that anti-parasitic drugs may have their greatest impact. 50,53,54 Consistent with the post-GMEP view, all theoretical, observational and experimental studies since then confirm that population-wide drug administration campaigns have limited impact upon the high levels of transmission commonly observed in sub-Saharan Africa, even when layered upon an effective vector control intervention [48][49][50] : Previous trials using the combination of MDA and residual spraying in the Sudan savanna of Africa had achieved variable degrees of control, but all had failed to interrupt transmission.…”

“…52 The fact that sporogonic stage infections can persist longer than single complete doses of therapeutic drugs enables P. falciparum populations to partially evade such exclusively human-directed chemical attack for the simple reason that mosquitoes do not take drugs. Although the benefits of controlling reservoirs of human parasite infection with therapeutic drugs are intuitive, appealing, and well established, only limited impact can be expected where high transmission levels persist 18,46,50,53 and the dangers of applying strong selection pressure for drug resistance upon robust parasite populations are also obvious. 50 These observations have a number of very important and direct implications for the final stages of P. falciparum elimination.…”

Malaria in Middle Childhood and Adolescence

“…In this situation, mathematical models of malaria can provide insight because they can simultaneously model multiple interventions and take into account the dynamics of malaria transmission, especially the mass effects of community interventions. For example, modeling of the cost-effectiveness of community-wide IST highlighted its value in medium-high transmission settings among school-age children, but only if it was continued indefinitely (Crowell and others 2013). The combined use of mathematical modeling and economic evaluation can help identify which interventions should be targeted specifically toward school-age children and which interventions should be delivered as part of community-wide malaria control.…”