Residual malaria transmission dynamics varies across The Gambia despite high coverage of control interventions
Date
2017-11
Journal Title
Journal ISSN
Volume Title
Publisher
PLOS ONE
Abstract
Over the last decades, malaria has declined substantially in The Gambia but its transmission
has not been interrupted. In order to better target control interventions, it is essential to
understand the dynamics of residual transmission. This prospective cohort study was conducted
between June 2013 and April 2014 in six pairs of villages across The Gambia. Blood
samples were collected monthly during the transmission season (June-December) from all
residents aged 6 months (4,194 individuals) and then in April (dry season). Entomological
data were collected monthly throughout the malaria transmission season. Ownership of
Long-Lasting Insecticidal Nets was 71.5% (2766/3869). Incidence of malaria infection and
clinical disease varied significantly across the country, with the highest values in eastern
(1.7/PYAR) than in central (0.2 /PYAR) and western (0.1/PYAR) Gambia. Malaria infection
at the beginning of the transmission season was significantly higher in individuals who slept
outdoors (HR = 1.51, 95% CI: 1.02±2.23, p = 0.04) and in those who had travelled outside
the village (HR = 2.47, 95% CI: 1.83±3.34, p <0.01). Sub-patent infections were more common
in older children (HR = 1.35, 95% CI: 1.04±1.6, p <0.01) and adults (HR = 1.53, 95%
CI: 1.23±1.89, p<0.01) than in younger children. The risk of clinical malaria was significantly
higher in households with at least one infected individual at the beginning of the transmission
season (HR = 1.76, p<0.01). Vector parity was significantly higher in the eastern part of
the country, both in the south (90.7%, 117/129, p<0.01) and the north bank (81.1%, 227/
280, p<0.01), than in the western region (41.2%, 341/826), indicating higher vector survival.
There is still significant residual malaria transmission across The Gambia, particularly in theeastern region. Additional interventions able to target vectors escaping Long-Lasting Insecticidal
Nets and indoor residual spraying are needed to achieve malaria elimination.
Description
Keywords
sub-Saharan Africa, Gambia, (HR = 1.51, 95% CI, 1.02±2.23, p = 0.04), Predominantly, Residual, Malaria Transmission, Dynamics, Interventions
Citation
Mwesigwa J, Achan J, Di Tanna GL, Affara M, Jawara M, Worwui A, et al. (2017) Residual malaria transmission dynamics varies across The Gambia despite high coverage of control interventions. PLoS ONE 12(11): e0187059.