Geo-epidemiology of malaria incidence in the Vhembe District to guide targeted elimination strategies, South-Africa, 2015-2018: a local resurgence

Abstract

In South Africa, the population at risk of malaria is 10% (around six million inhabitants) and concern only three provinces of which Limpopo Province is the most affected, particularly in Vhembe District. As the elimination approaches, a finer scale analysis is needed to accelerate the results. Therefore, in the process of refining local malaria control and elimination strategies, the aim of this study was to identify and describe malaria incidence patterns at the locality scale in the Vhembe District, Limpopo Province, South Africa. The study area comprised 474 localities in Vhembe District for which smoothed malaria incidence curve were fitted with functional data method based on their weekly observed malaria incidence from July 2015 to June 2018. Then, hierarchical clustering algorithm was carried out considering different distances to classify the 474 smoothed malaria incidence curves. Thereafter, validity indices were used to determine the number of malaria incidence patterns. The cumulative malaria incidence of the study area was 4.1 cases/1000 person-years. Four distinct patterns of malaria incidence were identified: high, intermediate, low and very low with varying characteristics. Malaria incidence increased across transmission seasons and patterns. The localities in the two highest incidence patterns were mainly located around farms, and along the rivers. Some unusual malaria phenomena in Vhembe District were also highlighted as resurgence. Four distinct malaria incidence patterns were found in Vhembe District with varying characteristics. Findings show also unusual malaria phenomena in Vhembe District that hinder malaria elimination in South Africa. Assessing the factors associated with these unusual malaria phenome would be helpful on building innovative strategies that lead South Africa on malaria elimination.

Figure 1

The study localities across Vhembe District in Limpopo Province, South Africa. Maps were produced by the authors using QGIS software (version 3.10.1., QGIS Development Team 2020. Open-Source Geospatial Foundation Project), OpenStreetMap and Shapefiles downloaded from websites^,.

Figure 2

Smoothing and Identification of malaria incidence patterns from July 2015 to June 2018. Observed incidence localities (A), smoothed incidence localities (B), smoothed incidence localities of patterns (C) and smoothed cumulative incidence by pattern (D): very low (blue), low (green), Intermediate (orange) and high (red).

Figure 3

Smoothed incidence localities and cumulative incidence for each pattern from July 2015 to June 2018: Very low (A—blue), Low (B—green), Intermediate (C—orange) and High (D—red).

Figure 4

Spatial distribution of malaria incidence pattern localities in Vhembe District: very low (blue), low (green), intermediate (orange) and high (red). Maps were produced by the authors using QGIS software (version 3.10.1., QGIS Development Team 2020. Open-Source Geospatial Foundation Project) and Shapefiles downloaded from websites^,.