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. 2015 Jan 8;9(1):e3413.
doi: 10.1371/journal.pntd.0003413. eCollection 2015 Jan.

Systematic review of sub-microscopic P. vivax infections: prevalence and determining factors

Qin Cheng  1 , Jane Cunningham  2 , Michelle L Gatton  3
Affiliations

Systematic review of sub-microscopic P. vivax infections: prevalence and determining factors

Qin Cheng et al. PLoS Negl Trop Dis. .

Abstract

Background: Sub-microscopic (SM) Plasmodium infections represent transmission reservoirs that could jeopardise malaria elimination goals. A better understanding of the epidemiology of these infections and factors contributing to their occurrence will inform effective elimination strategies. While the epidemiology of SM P. falciparum infections has been documented, that of SM P. vivax infections has not been summarised. The objective of this study is to address this deficiency.

Methodology/principal findings: A systematic search of PubMed was conducted, and results of both light microscopy (LM) and polymerase chain reaction (PCR)-based diagnostic tests for P. vivax from 44 cross-sectional surveys or screening studies of clinical malaria suspects were analysed. Analysis revealed that SM P. vivax is prevalent across different geographic areas with varying transmission intensities. On average, the prevalence of SM P. vivax in cross-sectional surveys was 10.9%, constituting 67.0% of all P. vivax infections detected by PCR. The relative proportion of SM P. vivax is significantly higher than that of the sympatric P. falciparum in these settings. A positive relationship exists between PCR and LM P. vivax prevalence, while there is a negative relationship between the proportion of SM P. vivax and the LM prevalence for P. vivax. Amongst clinical malaria suspects, however, SM P. vivax was not identified.

Conclusions/significance: SM P. vivax is prevalent across different geographic areas, particularly areas with relatively low transmission intensity. Diagnostic tools with sensitivity greater than that of LM are required for detecting these infection reservoirs. In contrast, SM P. vivax is not prevalent in clinical malaria suspects, supporting the recommended use of quality LM and rapid diagnostic tests in clinical case management. These findings enable malaria control and elimination programs to estimate the prevalence and proportion of SM P. vivax infections in their settings, and develop appropriate elimination strategies to tackle SM P. vivax to interrupt transmission.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Prevalence of LM (light microscopy, blue bar) and SM (sub-microscopy, red bar) P. vivax in cross-sectional surveys.
The total height of each bar (blue + red) represents the PCR prevalence. Countries where data were collected and their corresponding references (detailed in Table 1) are shown on the x-axis.
Figure 2
Figure 2. Prevalence of LM (light microscopy, blue bar) and SM (sub-microscopy, red bar) of sympatric P. falciparum in cross-sectional surveys.
Total height of each bar (blue + red) represents the PCR prevalence. Countries where data were collected and their corresponding references (detailed in Table 1) are shown on the x-axis.
Figure 3
Figure 3. Relative proportion of SM (sub-microscopy) P. vivax in cross-sectional surveys.
Countries where data were collected and their corresponding references (detailed in Table 1) are shown on the x-axis.
Figure 4
Figure 4. Relative proportion of sympatric SM (sub-microscopy) P. falciparum in cross-sectional surveys.
Countries where data were collected and their corresponding references (detailed in Table 1) are shown on the x-axis.
Figure 5
Figure 5. A) Comparison of SM (sub-microscopy) P. vivax and SM (sub-microscopy) P. falciparum prevalence (mean with 95% CI) in 31 cross-sectional surveys.
B) Comparison of relative proportions of SM (sub-microscopy) P. vivax and P. falciparum (mean with 95% CI) in 31 cross-sectional surveys.
Figure 6
Figure 6. Relationship between LM (light microscopy) and PCR determined P. vivax prevalence in 31 cross-sectional surveys.
Figure 7
Figure 7. Relationship between LM (light microscopy) and SM (sub-microscopy) P. vivax prevalence in 31 cross-sectional surveys.
Figure 8
Figure 8. Prevalence of LM (light microscopy, blue bar) and SM (sub-microscopy, red bar) P. vivax in clinical malaria suspects.
Total height of the bar (blue + red) represents the PCR prevalence.
Figure 9
Figure 9. Prevalence of LM (light microscopy, blue bar) and SM (sub-microscopy, red bar) P. falciparum in clinical malaria suspects.
Total height of bar (blue + red) represents PCR prevalence.
See this image and copyright information in PMC

References

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