Improving the efficiency of reactive case detection for malaria elimination in southern Zambia: a cross-sectional study

Abstract

Background: Reactive case detection (RCD) seeks to enhance malaria surveillance and control by identifying and treating parasitaemic individuals residing near index cases. In Zambia, this strategy starts with passive detection of symptomatic incident malaria cases at local health facilities or by community health workers, with subsequent home visits to screen-and-treat residents in the index case and neighbouring (secondary) households within a 140-m radius using rapid diagnostic tests (RDTs). However, a small circular radius may not be the most efficient strategy to identify parasitaemic individuals in low-endemic areas with hotspots of malaria transmission. To evaluate if RCD efficiency could be improved by increasing the probability of identifying parasitaemic residents, environmental risk factors and a larger screening radius (250 m) were assessed in a region of low malaria endemicity. Methods: Between January 12, 2015 and July 26, 2017, 4170 individuals residing in 158 index and 531 secondary households were enrolled and completed a baseline questionnaire in the catchment area of Macha Hospital in Choma District, Southern Province, Zambia. Plasmodium falciparum prevalence was measured using PfHRP2 RDTs and quantitative PCR (qPCR). A Quickbird ™ high-resolution satellite image of the catchment area was used to create environmental risk factors in ArcGIS, and generalized estimating equations were used to evaluate associations between risk factors and secondary households with parasitaemic individuals. Results: The parasite prevalence in secondary (non-index case) households was 0.7% by RDT and 1.8% by qPCR. Overall, 8.5% (n = 45) of secondary households had at least one resident with parasitaemia by qPCR or RDT. The risk of a secondary household having a parasitaemic resident was significantly increased in proximity to higher order streams and marginally with increasing distance from index households. The adjusted OR for proximity to third-and fifth-order streams were 2.97 (95% CI 1.04-8.42) and 2.30 (95% CI 1.04-5.09), respectively, and that for distance to index households for each 50 m was 1.24 (95% CI 0.98-1.58).

Sociodemographic and Economic Traits That Affect Malaria Prevalence in Sussundenga Village, Mozambique.

“…In this study, malaria prevalence was 31.6 % for Sussundenga Village, higher than the prevalence recorded in Chimoio city [16] of 20.1 % In the neighboring Zimbabwe, malaria prevalence was 19.5 % in Mutare and 50.9 % in Mutasa districts in 2016. [17] and in Zambia a study reported parasite prevalence between 0.7 and 1.8 % [18]. And 34 % in…”

Sustained Malaria Transmission despite Reactive Screen-and-Treat in a Low-Transmission Area of Southern Zambia

“…Many of these findings are consistent with prior findings using epidemiologic and genetic data to identify focal transmission and can inform the National Malaria Elimination Programme on how to efficiently deploy interventions to interrupt transmission and achieve malaria elimination. 9 , 10 , 12 , 21 , 22 , 38 Many previous studies have focused on the spatial extent and methods for screening and timing of potential follow-up visits in programs. 21 , 23 , 39 , 40 Reactive screen-and-treat is now being implemented across several sub-Saharan African countries using similar methods as in southern Zambia.…”

“… 9 , 10 , 12 , 21 , 22 , 38 Many previous studies have focused on the spatial extent and methods for screening and timing of potential follow-up visits in programs. 21 , 23 , 39 , 40 Reactive screen-and-treat is now being implemented across several sub-Saharan African countries using similar methods as in southern Zambia. 9 , 11 , 16 These have led to improved surveillance and an identification of an increased number of parasitemic individuals but have yet to successfully reduce transmission or achieve elimination.…”

“…However, it is unclear to what extent reactive screen-and-treat is effective in further reducing transmission and eliminating the parasite reservoir. 9,17,19,[21][22][23] To assess the spatial and temporal effectiveness of reactive screen-and-treat in a low-transmission setting within the catchment area of Macha Hospital in Choma district, Southern Province, Zambia, the screening radius was extended to 250 m, and follow-up visits were added at 30 and 90 days. The 250-m radius was chosen based on a previous study where 92% of cases were detected within this range.…”

“…However, it is unclear to what extent reactive screen-and-treat is effective in further reducing transmission and eliminating the parasite reservoir. 9 , 17 , 19 , 21 – 23 …”