Reactive case-detection of malaria in Pailin Province, Western Cambodia: lessons from a year-long evaluation in a pre-elimination setting

Hustedt, John; Canavati, Sara E.; Rang, Chandary; Ashton, Ruth A.; Khim, Nimol; Berne, Laura; Kim, Saorin; Sovannaroth, Siv; Ly, Po; Ménard, Didier; Cox, Jonathan; Meek, Sylvia; Roca-Feltrer, Arantxa

doi:10.1186/s12936-016-1191-z

Cited by 49 publications

(51 citation statements)

References 30 publications

(43 reference statements)

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“…At such a large proportion of village screened, targeted screening around an index case only had a marginal gain compared to randomly screening the same proportion of village households. These results are consistent with recent findings from Pailin Province, Cambodia where few cases were detected through reactively screening index houses and neighbours [23]. …”

Section: Discussionsupporting

confidence: 93%

Limitations of malaria reactive case detection in an area of low and unstable transmission on the Myanmar–Thailand border

Parker

Landier

Seidlein

et al. 2016

Malar J

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BackgroundReactive case detection is an approach that has been proposed as a tool for malaria elimination in low-transmission settings. It is an intuitively justified approach based on the concept of space–time clustering of malaria cases. When an index malaria clinical case is detected, it triggers reactive screening and treatment in the index house and neighbouring houses. However, the efficacy of this approach at varying screening radii and malaria prevalence remains ill defined.MethodsData were obtained from a detailed demographic and geographic surveillance study in four villages on the Myanmar–Thailand border. Clinical cases were recorded at village malaria clinics and were linked back to patients’ residencies. These data were used to simulate the efficacy of reactive case detection for clinical cases using rapid diagnostic tests (RDT). Simulations took clinical cases in a given month and tabulated the number of cases that would have been detected in the following month at varying screening radii around the index houses. Simulations were run independently for both falciparum and vivax malaria. Each simulation of a reactive case detection effort was run in comparison with a strategy using random selection of houses for screening.ResultsIn approximately half of the screenings for falciparum and 10% for vivax it would have been impossible to detect any malaria cases regardless of the screening strategy because the screening would have occurred during times when there were no cases. When geographically linked cases were present in the simulation, reactive case detection would have only been successful at detecting most malaria cases using larger screening radii (150-m radius and above). At this screening radius and above, reactive case detection does not perform better than random screening of an equal number of houses in the village. Screening within very small radii detects only a very small proportion of cases, but despite this low performance is better than random screening with the same sample size.ConclusionsThe results of these simulations indicate that reactive case detection for clinical cases using RDTs has limited ability in halting transmission in regions of low and unstable transmission. This is linked to high spatial heterogeneity of cases, acquisition of malaria infections outside the village, as well missing asymptomatic infections. When cases are few and sporadic, reactive case detection would result in major time and budgetary losses.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1631-9) contains supplementary material, which is available to authorized users.

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Section: Discussionsupporting

confidence: 93%

Limitations of malaria reactive case detection in an area of low and unstable transmission on the Myanmar–Thailand border

Parker

Landier

Seidlein

et al. 2016

Malar J

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“…However, there is limited evidence to guide how household-based RCD is conducted and whether it has any impact on transmission [85–87]. Where risk is driven more by behaviours than by household location, malaria programmes could adapt RCD to instead screen and treat social contacts of the index case who engage in known risk behaviours, such as forest work colleagues, as a form of “socio-behavioural RCD”.…”

Section: Introductionmentioning

confidence: 99%

Surveillance and response for high-risk populations: what can malaria elimination programmes learn from the experience of HIV?

Jacobson

Cueto

Smith

et al. 2017

Malar J

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To eliminate malaria, malaria programmes need to develop new strategies for surveillance and response appropriate for the changing epidemiology that accompanies transmission decline, in which transmission is increasingly driven by population subgroups whose behaviours place them at increased exposure. Conventional tools of malaria surveillance and response are likely not sufficient in many elimination settings for accessing high-risk population subgroups, such as mobile and migrant populations (MMPs), given their greater likelihood of asymptomatic infections, illegal risk behaviours, limited access to public health facilities, and high mobility including extended periods travelling away from home. More adaptive, targeted strategies are needed to monitor transmission and intervention coverage effectively in these groups. Much can be learned from HIV programmes’ experience with “second generation surveillance”, including how to rapidly adapt surveillance and response strategies to changing transmission patterns, biological and behavioural surveys that utilize targeted sampling methods for specific behavioural subgroups, and methods for population size estimation. This paper reviews the strategies employed effectively for HIV programmes and offers considerations and recommendations for adapting them to the malaria elimination context.

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“…RCD with antimalarial drugs has previously been shown to have only a minimal or moderate impact on reaching elimination (31)(32)(33)(34). Post-elimination, we find that RCD can help sustain a near-eliminated state, but only under certain performance criteria.…”

Section: Discussionmentioning

confidence: 59%

Effective strategies for preventing reestablishment of malaria in areas with recent elimination and high transmission potential

Gerardin

Bever

Bridenbecker

et al. 2019

Preprint

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Maintaining zero transmission after malaria elimination will be a challenging task for many countries where malaria is still endemic. When local transmission potential is high, and importation of malaria infections continues from neighboring areas with ongoing transmission, malaria programs must develop robust surveillance and outbreak response systems. However, the requirements for such systems remain unclear. Using an agent-based, spatial microsimulation model of two areas in southern Zambia, where elimination efforts are currently underway, we compare the ability of various routine and reactive intervention packages to maintain near-zero prevalence in the face of continued importation. We find that in formerly moderate-transmission areas, high treatment rate of symptomatic malaria is sufficient to prevent reestablishment of malaria. Routine redistributions of insecticide-treated nets and reactive case detection with antimalarial drugs cannot completely compensate for inadequate case management. In formerly high-transmission areas, excellent case management and maintenance of good bednet coverage are both required to prevent resurgence, and outbreak response with antimalarial drugs or additional vector control is also necessary. These results begin to describe the essential criteria for operations that successfully prevent reestablishment of malaria post-elimination and highlight the need for both long-term, sustainable excellence in primary care and comprehensive surveillance that feeds into rapid and flexible outbreak response. Author SummaryThe global community is working toward malaria elimination, but some areas will eliminate before others. Eliminated areas will need to develop intervention programs capable of preventing imported infections from leading to reestablishment, a particular challenge when transmission was previously very high. Past experience has shown that stopping elimination interventions leads to massive resurgence, but it is unclear which interventions must be continued, which can be stopped to conserve resources, and what new interventions should be deployed. Using a simulation model built to capture malaria transmission and intervention history of two areas that recently made enormous progress toward elimination, we tested how well different intervention programs were able to prevent reestablishment of malaria. We found that treating as many symptomatic cases as possible was the single most important intervention to implement. In some contexts, this intervention alone was sufficient to prevent reestablishment. Other areas with historically higher transmission required maintaining vector control to contain mosquito populations. Localized outbreak response with antimalarial drugs or additional vector control was also necessary and predicted to be a highly efficient use of resources. These findings provide quantitative guidance for policy-makers considering how to stratify eliminated areas and plan new operational modes for the post-elimination era.

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Reactive case-detection of malaria in Pailin Province, Western Cambodia: lessons from a year-long evaluation in a pre-elimination setting

Cited by 49 publications

References 30 publications

Limitations of malaria reactive case detection in an area of low and unstable transmission on the Myanmar–Thailand border

Limitations of malaria reactive case detection in an area of low and unstable transmission on the Myanmar–Thailand border

Surveillance and response for high-risk populations: what can malaria elimination programmes learn from the experience of HIV?

Effective strategies for preventing reestablishment of malaria in areas with recent elimination and high transmission potential

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