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Fitsum G Tadesse
Malaria and Neglected Tropical Diseases Directorate, Armauer Hansen Research Institute, PO Box 1005, Addis Ababa, Ethiopia
Corresponding Author
ORCiD: https://orcid.org/0000-0003-1931-1442
License:
This work is licensed under a CC BY 4.0 License. Read Full License
Background: As countries move to malaria elimination, detecting and targeting asymptomatic malaria infections might be needed. Here, we investigated the epidemiology and detectability of asymptomatic Plasmodium falciparum and P. vivax infections in different transmission settings in Ethiopia.
Method: A total of 1093 dried blood spot (DBS) samples were collected from afebrile and apparently healthy individuals across ten study sites in Ethiopia from 2016 to 2020. Of these, 862 were from community and 231 from school based cross-sectional surveys. Malaria infection status was determined by microscopy or rapid diagnostics tests (RDT) and 18S rRNA based nested PCR (nPCR). The annual parasite index (API) was used to classify endemicity as low (API>0 and<5), moderate (API ≥5 and <100) and high transmission (API≥100) and detectability of infections was assessed in these settings.
Results: In community surveys, the overall prevalence of asymptomatic Plasmodium infections by microscopy/RDT, nPCR and all methods combined was 12.2% (105/860), 21.6% (183/846) and 24.1% (208/862), respectively. The proportion of nPCR positive infections that was detectable by microscopy/RDT was 48.7% (73/150) for P. falciparum and 4.6% (2/44) for P. vivax. Compared to low transmission settings, the likelihood of detecting infections by microscopy/RDT was increased in moderate (Adjusted odds ratio [AOR]: 3.4; 95% confidence interval [95%CI]:1.6-7.2, P=0.002) and high endemic settings (AOR=5.1; 95%CI=2.6-9.9, P<0.001). After adjustment for site and correlation between observations from the same survey, the likelihood of detecting asymptomatic infections by microscopy/RDT (AOR per year increase = 0.95, 95%CI=0.9-1.0, P=0.013) declined with age.
Conclusion: Conventional diagnostics missed nearly half of the asymptomatic Plasmodium reservoir detected by nPCR. The detectability of infections was particularly low in older age groups and low transmission settings. These findings highlight the need for sensitive diagnostic tools to detect the entire parasite reservoir and potential infection transmitters.
Keywords
Plasmodium infection, elimination, asymptomatic, transmission, nPCR, detectability, density distribution
Figure 1
Figure 2
This is a list of supplementary files associated with this preprint. Click to download.
- Additionaltable3.docx
Supplementary Table 3. GEE model for association of malaria infection prevalence using all methods combined (nPCR and/or microscopy/RDT) among community survey samples with sample characteristics such as gender, age category, level of endemicity from 2016-2020, Ethiopia
- Additionaltable2.docx
Supplementary Table-2. Concordance of RDT and Microscopy detected samples compared to nPCR among the study participants, 2016-2020
- Additionaltable1.docx
Supplementary Table 1. School based prevalence of asymptomatic malaria in selected sites from different transmission settings using nPCR and microscopy/RDT from 2016- 2018, Ethiopia
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CURRENT STATUS: Published
View the published article at Malaria Journal.
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Posted 13 Oct, 2020
No community comments so far
Editorial decision: Minor Revision
On 20 Dec, 2020
Review #1 received
Received 06 Dec, 2020
Reviewer #1 agreed
On 15 Nov, 2020
Reviewers invited
Invitations sent on 26 Oct, 2020
Editor assigned
On 07 Oct, 2020
Submission checks complete
On 06 Oct, 2020
Editor invited
On 06 Oct, 2020
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Subject Areas
Infectious Diseases
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A new preprint design is coming!
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See the published version of this preprint at Malaria Journal.
This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Research
Fitsum G Tadesse
Malaria and Neglected Tropical Diseases Directorate, Armauer Hansen Research Institute, PO Box 1005, Addis Ababa, Ethiopia
Corresponding Author
ORCiD: https://orcid.org/0000-0003-1931-1442
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Published
View the published article at Malaria Journal.
Version 1
Posted 13 Oct, 2020
No community comments so far
Editorial decision: Minor Revision
On 20 Dec, 2020
Review #1 received
Received 06 Dec, 2020
Reviewer #1 agreed
On 15 Nov, 2020
Reviewers invited
Invitations sent on 26 Oct, 2020
Editor assigned
On 07 Oct, 2020
Submission checks complete
On 06 Oct, 2020
Editor invited
On 06 Oct, 2020
First submitted
On 03 Oct, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Infectious Diseases
License:
This work is licensed under a CC BY 4.0 License. Read Full License
View the published article at Malaria Journal.
Background: As countries move to malaria elimination, detecting and targeting asymptomatic malaria infections might be needed. Here, we investigated the epidemiology and detectability of asymptomatic Plasmodium falciparum and P. vivax infections in different transmission settings in Ethiopia.
Method: A total of 1093 dried blood spot (DBS) samples were collected from afebrile and apparently healthy individuals across ten study sites in Ethiopia from 2016 to 2020. Of these, 862 were from community and 231 from school based cross-sectional surveys. Malaria infection status was determined by microscopy or rapid diagnostics tests (RDT) and 18S rRNA based nested PCR (nPCR). The annual parasite index (API) was used to classify endemicity as low (API>0 and<5), moderate (API ≥5 and <100) and high transmission (API≥100) and detectability of infections was assessed in these settings.
Results: In community surveys, the overall prevalence of asymptomatic Plasmodium infections by microscopy/RDT, nPCR and all methods combined was 12.2% (105/860), 21.6% (183/846) and 24.1% (208/862), respectively. The proportion of nPCR positive infections that was detectable by microscopy/RDT was 48.7% (73/150) for P. falciparum and 4.6% (2/44) for P. vivax. Compared to low transmission settings, the likelihood of detecting infections by microscopy/RDT was increased in moderate (Adjusted odds ratio [AOR]: 3.4; 95% confidence interval [95%CI]:1.6-7.2, P=0.002) and high endemic settings (AOR=5.1; 95%CI=2.6-9.9, P<0.001). After adjustment for site and correlation between observations from the same survey, the likelihood of detecting asymptomatic infections by microscopy/RDT (AOR per year increase = 0.95, 95%CI=0.9-1.0, P=0.013) declined with age.
Conclusion: Conventional diagnostics missed nearly half of the asymptomatic Plasmodium reservoir detected by nPCR. The detectability of infections was particularly low in older age groups and low transmission settings. These findings highlight the need for sensitive diagnostic tools to detect the entire parasite reservoir and potential infection transmitters.
Figure 1
Figure 2
This is a list of supplementary files associated with this preprint. Click to download.
- Additionaltable3.docx
Supplementary Table 3. GEE model for association of malaria infection prevalence using all methods combined (nPCR and/or microscopy/RDT) among community survey samples with sample characteristics such as gender, age category, level of endemicity from 2016-2020, Ethiopia
- Additionaltable2.docx
Supplementary Table-2. Concordance of RDT and Microscopy detected samples compared to nPCR among the study participants, 2016-2020
- Additionaltable1.docx
Supplementary Table 1. School based prevalence of asymptomatic malaria in selected sites from different transmission settings using nPCR and microscopy/RDT from 2016- 2018, Ethiopia
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