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. 2017 Aug 3;12(8):e0182189.
doi: 10.1371/journal.pone.0182189. eCollection 2017.

Substantial asymptomatic submicroscopic Plasmodium carriage during dry season in low transmission areas in Senegal: Implications for malaria control and elimination

Makhtar Niang  1 , Laty Gaye Thiam  1 , Rokhaya Sane  1 , Nafissatou Diagne  2 , Cheikh Talla  3 , Souleymane Doucoure  2 , Joseph Faye  3 , Fode Diop  1 , Abdoulaye Badiane  3 , Babacar Diouf  1 , Diogop Camara  1 , Fatoumata Diene-Sarr  3 , Cheikh Sokhna  2 , Vincent Richard  3 , Aissatou Toure-Balde  1
Affiliations

Substantial asymptomatic submicroscopic Plasmodium carriage during dry season in low transmission areas in Senegal: Implications for malaria control and elimination

Makhtar Niang et al. PLoS One. .

Abstract

Background: In the progress towards malaria elimination, the accurate diagnosis of low-density asymptomatic infections is critical. Low-density asymptomatic submicroscopic malaria infections may act as silent reservoirs that maintain low-level residual malaria transmission in the community. Light microscopy, the gold standard in malaria diagnosis lacks the sensitivity to detect low-level parasitaemia. In this study, the presence and prevalence of submicroscopic Plasmodium carriage were investigated to estimate the parasites reservoir among asymptomatic individuals living in low transmission areas in Dielmo and Ndiop, Senegal during the dry season.

Methods: A total of 2,037 blood samples were collected during cross-sectional surveys prior the malaria transmission season in July 2013 (N = 612), June 2014 (N = 723) and June 2015 (N = 702) from asymptomatic individuals living in Dielmo and Ndiop, Senegal. Samples were used to determine the prevalence of submicroscopic Plasmodium carriage by real time PCR (qPCR) in comparison to microscopy considered as gold standard.

Results: The prevalence of submicroscopic Plasmodium carriage was 3.75% (23/612), 12.44% (90/723) and 6.41% (45/702) in 2013, 2014 and 2015, respectively. No Plasmodium carriage was detected by microscopy in 2013 while microscopy-based prevalence of Plasmodium carriage accounted for only 0.27% (2/723) and 0.14% (1/702) in 2014 and 2015, respectively. Plasmodium falciparum accounted for the majority of submicroscopic infections and represented 86.95% (20/23), 81.11% (73/90) and 95.55 (43/45) of infections in 2013, 2014 and 2015 respectively.

Conclusion: Low-density submicroscopic asymptomatic Plasmodium carriage is common in the study areas during the dry season indicating that traditional measures are insufficient to assess the scale of parasite reservoir when transmission reaches very low level. Control and elimination strategies may wish to consider using molecular methods to identify parasites carriers to guide Mass screening and Treatment strategies.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Study design for determination of Plasmodium carriage in Dielmo and Ndiop villages.
Fig 2
Fig 2. Melt curves analysis showing the qualitative detection and discrimination of the four malaria species (P. falciparum, P. vivax, P. malariae and P. ovale) using nested real time PCR.
Fig 3
Fig 3. Frequency of submicroscopic Plasmodium parasite carriage according to age groups.
See this image and copyright information in PMC

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